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NEW WEBSITE on FOUR-STROKE DESIGN

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Posted by: EricGorr

Hey guys, check out this new joint venture between Professor Gordon P. Blair and Hans Herman. Professor Blair is well know for his development of design and simulation software for two and four stroke engines. Professor Blair is a motorcycle racing enthusiast and many case studies are referenced in his books published by the SAE. Hans Herman headed the development team on Nissan’s IRL engine back in the mid-1990s. Hans is highly regarded in automotive racing as a cylinder head and cam specialist.

Their new company, Professor Blair and Associates, offers design and simulation software for four-stroke top end components, and they also offer consulting services.

There are some interesting AVI files on the site, that enable tuners to design a cylinder head and observe a full motion video on the mechanical components.
Its great stuff and I encourage you guys to check it out! If you have any questions of want to start a thread topic and discussion based on the info from the Blair site, please feel free. We’re always looking for interesting things to talk about in this forum.

Rich and I are going to attend a demonstration of the new software on December 9th and we’ll write a tech article on the benefits of the software and how it can be applied for specific applications on single cylinder four-stroke dirt bike engines.

Check out this site by clicking on this link
http://www.profblairandassociates.com/

Check out this AVI file on a 4-valve pentroof head
http://www.profblairandassociates.c...HeadLayout.html

This link is to Amazon and features info on Professor Blair’s latest book “DESIGN & SIMULATION of FOUR-STROKE ENGINES”
http://www.amazon.com/exec/obidos/t...=glance&s=books


Posted by: biglou

Wow! Thanks Eric. Great stuff. :thumb:

btw-Did I notice a little intake valve-piston clash in those AVI's? Maybe the cam chain jumped a tooth!


Posted by: gblair

to Big Lou
you did notice piston and valve clash and the software calculates the extent of that clash so the designer can make the piston cut-outs the correct size and placement...... prof. blair and associates


Posted by: bclapham

Welcome to the the website Professor Blair!

do you have a homepage of youe research group? i am sure it would make interesting reading and refernce also.

Thanks

Bruce Clapham


Posted by: Rich Rohrich

Welcome to DRN Professor Blair and thanks for all your contributions to motorcyling. A lot of us would be would still be rubbing two sticks together trying to make horsepower without your huge body of work. I regularly blame YOU when people ask me why my apartment looks like the Library of Congress :thumb:

Looks like the aggregate Engine IQ of this place just shot WAY UP


Posted by: IrishEKU

Welcome Aboard Prof. Blair!


Posted by: gblair

to B Clapham
..if you go to our web site (www.profblairandassociates.com) you will find a links page which link onb that can take you directly to the QUB web site for IC Engines where I used to work before I retired at the end of 1996.


Posted by: gblair

to Rich Rohrich
..as to your apartment..may I suggest a shovel used with the front door open through which you heave all those ancient QUB papers!


Posted by: gblair

to IrishEKU thanks...!


Posted by: gblair

to B Clapham
...may I also suggest that you will find even more info of interest on the Optimum Power website (www.optimum-power.com) who have much to do with dirt bikes of all kinds, who sell the VIRTUAL ENGINES 2-stroke and 4-stroke engine sumulation software, who design and produce EFI systems for dirt bikes, who sponsor R&D at QUB which I help with, and last and far from least employ at least 4 of my ex-students from QUB in Belfast!


Posted by: bclapham

Thanks for your feedback Prof. Blair, please feel free to come here for a chat at anytime. We have quite a few tuners on here that i am sure will have many questions for you if you have the time to answer Personally, i am very much a begginer at understanding engine performance so i am here to learn.

its also great to see that you look after the old members from the group, i found it most amusing when Eric Gorr told me some of the Thesis titles from your students, porting Kart engines sounds much more interesting than some of the chemistry titles i have read!

regards

Bruce


Posted by: Rich Rohrich

Quote:
Originally posted by gblair
to Rich Rohrich
..as to your apartment..may I suggest a shovel used with the front door open through which you heave all those ancient QUB papers!


... and replace them with WHAT? The fine technical musing of the useless twits at Motocross Action?


Posted by: bclapham

Quote:
Originally posted by Rich Rohrich
... and replace them with WHAT? The fine technical musing of the useless twits at Motocross Action?


Yep, as long as they can get their writings past the peer review process!


Posted by: IrishEKU

Quote:
Originally posted by gblair
to Rich Rohrich
..as to your apartment..may I suggest a shovel used with the front door open through which you heave all those ancient QUB papers!


Rich use a shovel? More like a moded skid loader with one of his special fuel mixes, and hydraulics worked over to apply the most lifting power with no loss to engine output.


Posted by: steve125

Welcome professor Blair! Have there been any new advances with high performance two strokes recently or in the future you would like to share?


Posted by: EricGorr

Professor Blair emailed me with a gracious offer to invite others who might be interested in his software demo session. We came up with a day and time based on the professor’s tight time schedule.
December 8th, Sunday afternoon (Noon to whenever) at the Rolling Meadows Holiday Inn, Fond du Lac Wisconsin, at the corners of Rt.41 and Rt.151
Fond du Lac is 1 hour north of Milwaukee in the great engine building state of Wisconsin.
The size of the conference room for the presentation will be based on how many people email me in advance. There’s no charge for the demonstration.
If you’ve ever read any of Professor Blair’s books or technical papers this is a rare opportunity to meet him and discover the latest design tools in four-stroke engine technology.
Think of it as saving yourself 9,000 miles of driving to and from Belfast Northern Ireland. So on Sunday December 8th, send your wife and kids out to the mall to muddle through the masses of shoppers and come spend an afternoon with one of motorcycling’s most prolific engine innovators.

Email or call me to let me know you’re interested
Eric Gorr egorr@globaldialog.com 1-920-356-0741


Posted by: IrishEKU

Eric,

I can already say that I am sorry that I will miss an awesome conferance. My parents have already shipped a ticket for me to do X-Mass with them. Please post what you learned!


Posted by: cujet

I am thrilled to see Prof Blair here at the forums. Welcome!!! I have so many questions, as I am sure the rest of us do, I hope to see him here often! It is great to have such talented people in the dirt bike world.

I hope it is OK to ask a few questions here. I am a believer in the 5 valve head, is it really worth the 6% peak HP some claim?

Do you see significant increases in output for engines such as the YZ450F? If so, how much?

I have also wondered about an air cooled version of a modern high performance 4 stroke. Is there enough cooling in the air cooled design to allow high outputs? Of course this is a selfish question, as I continue to damage my radiators and cooling lines.

Chris


Posted by: Rich Rohrich

Quote:
Originally posted by EricGorr
Professor Blair emailed me with a gracious offer to invite others who might be interested in his software demo session. We came up with a day and time based on the professor’s tight time schedule.
December 8th, Sunday afternoon (Noon to whenever) at the Rolling Meadows Holiday Inn, Fond du Lac Wisconsin, at the corners of Rt.41 and Rt.151
Fond du Lac is 1 hour north of Milwaukee in the great engine building state of Wisconsin.


Finally a good reason to travel to the Hell of the North


Posted by: EricGorr

Oh RR$ you're such a Nattering Nabob of Negativism about our little unpopulated state, keep in mind that Wisconsin is truely the hub of the motorcycle universe with more motorcycles being manufactured and assembled here than any place in America, yes thats right were bigger than Socal and dam proud of it!

For you other guys dying to ask Professor Blair questions about engines, save them for the software demo because he's a very busy guy with consulting contracts with many of the OEM and aftermarket performance manufacturers.


Posted by: KYHU

Welcome Professor Blair. It's nice to see you on DRN. I was reading some of your papers on two-stroke engines not a week ago !

david


Posted by: gblair

to Steve125
..there is not a lot opf R&D going on these days on 2-strokes as the politicians and the manufacturers move towards mandating 4-stroke engines for just about every type of competition on the grounds of 'better emissions' although as most high performance engines (2st and 4st) emit some 6% CO I don't quite get the total point of the argument.


Posted by: gblair

to cujet
..regarding 5 valve engines the layout is so convoluted that any attempt to 'improve' the porting of the intake ports can be a bit fraught with problems as too heavy a hand with polishing or grinding ports can adversely affect the discharge coefficients of flow into the cylinder and the internal tumble characteristics of the flow which (by giving reduced intake mass flow and less effective combustion) can actually reduce the ensuing power output.
There is somewhat less danger of these effects with 4-valve engines.
..and air cooling is always less effective in any high performance engine than air cooling..two-strokes included.


Posted by: gblair

to cujet
..my apologies..that last piece should say...air cooling is always less effective that LIQUID cooling...


Posted by: gblair

to cujet
apologies again...my fingers won't type adequately this morning....
..air cooling of high performance engine is always less effective THAN liquid cooling..(2-strokes included)


Posted by: steve125

Thanks for answering Professor Blair! One more question I believe it to be fact that the majority of the flow through the transfer port window is at the first few millimeters of the port opening. If so then why are the transfer port windows generally so large?


Posted by: gblair

to steve125
..in a 2-stroke the flow in the first few crank degrees of transfer port opening (how many millimetres depends on the stroke) is normally backflow from the cylinder to the transfer ports and after that cylinder (exhaust) gas has been purged from the transfer ducts through the port the majority of the transfer port flow of fresh charge then takes place until just after bottom-dead-centre with a peak mass flow rate just about or before bdc..now all of that statement depends on the design of the exhaust pipe..but that would be normality in a high performance 2st engine....and as this is a 4-stroke forum I think I should only answer queries on that type of engine here.


Posted by: steve125

Thanks again for the reply, i understand now! Ok Ok no more 2 stk questions here :whiner: Eric or Rich, if Professor Blair would be so kind to answer some advanced 2 smoke questions in another forum can you set that up?  :thumb:


Posted by: SuzookKING

*drool starts pooling around keyboard


Posted by: Rich Rohrich

Quote:
Originally posted by gblair
....and as this is a 4-stroke forum I think I should only answer queries on that type of engine here.



Prof. Blair - Any technology that can promote an interesting discussion is more than welcome in this forum. You have an open door to discuss anything that you think fits the bill. :thumb:


Posted by: gblair

to R Rohrich
...thank you for the thought...and as to your overwhelming paper collection I have rescinded my views on my suggestion for the demise of those old QUB papers...so park the shovel and re-read SAE reference R-186 instead!


Posted by: steve125

Professor Blair, when testing two different expansion chambers on the same bike, a 03 kx 125. On a 3rd gear uphill close to peak rpm and at full throttle, one pipe makes the engine ping and the other does not. Both pipes "feel" to have the same overrev and peak power. The pipe that causes the ping, what is it doing and how can I best tune that out or is it a design problem with the pipe? Thanks!


Posted by: marcusgunby

Prof blair-another 2 stroke question if you dont mind,i have done alot of work tuning(mainly bolt ons) late model Crs-now one problem identified by Eric was the CR needed more blow down timing and we did this by putting a bush( 2mm larger pin than std) on the stop of the PV-now in testing and on the dyno i could feel no difference in the engine either in terms of roll on power or on full throttle-do some engines really not resond well to the 'ideal' blow down timing?could this be due to the CRs PV design not allowing the pv to sit close to the piston therefore the change in PV height really doesnt do much?


Posted by: gblair

gentlemen,
rather than turn this into a 2-stroke tuning forum, perhaps you could get someone to start a 2st tuning section and get your queries answered there...
however....one last 2st time here...
to Steve125 ...it sounds as if the 'pinging' pipe has either too small a mid-section diameter if both tailpipe diameters are the same or if both mid-section diameters are the same then the 'pinging pipe' has marginally too small a tailpipe (either way too much hot exhaust gas is getting trapped in the cylinder and the upshot is 'knocking'!)
..to Mr Gunby
when you raised the blowdown time-area did your mod increase the exhaust period for if it did then you lowered the trapped compression ratio and so it sounds as if one mod cancelled out the other in terms of power output.


Posted by: gblair

..so where are all the 4-stroke tuners...if they have been to that web site (www.profblairandassociates.com) I would have thought they would have a barrel-load of questions by now!..or are they all too heavily into tuning the Thanksgiving turkey that they have not time for extraneous matters like engine tuning....(there is no Thanksgiving Day in the UK)


Posted by: steve125

Professor Blair, the background on the pinging pipe is I almost sent it back to the maker. It had a blockage where the tailpipe connects to the last cone, the weld had burned through and was halfway blocked. I was able to clear most of it out but apparently not enough. The two pipes do share the same mid section diameter and tailpipe diameter. Your analogy is right on and i really appreciate it. Thanks again!......Ok Marcus we better untie all the 4 stroke guys now and let them in!


Posted by: LJW

Is it necesary to use a simulation (Virtual Engines) as a post processor of the 4st Head output data to see real world gains or losses?


Posted by: cujet

So, if the 5 valve head is difficult to get just right all the time, and 4 valves leave a bigger margin for error. What about straight shot intake ports as are common on street bikes and other high performance 4 strokes? Is there a big gain here?

I really do not like air cooling, however I had a hose burst and fill my boot, ouch!

Chris


Posted by: EricGorr

LJW I sent you an email at work inviting you to Professor Blair's software demo 12/8 12 noon in FDL. Hope to see you there! Don't ride your motorcycle, take a car its winter!

Cujet
The obvious problem of straight shot intakes on a dirt bike, you'd have to pitch the top end forward on an abrupt angle. Space is always a problem dirt bike designers are always struggling with. Take for example the exhaust system. On a lot of bikes it swirls around like a snake but still isn't long enough. The intake system is even worse because you've got to clear the rear shock. If you pitch the cylinder forward you'd have to slide the engine backwards which changes the CG of the bike, then you've got a handling problem. And its all interesting stuff for discussions


Posted by: gblair

to LJW
...to simulate the engine performance and get the power characteristics you have to use the VIRTUAL ENGINES approach..but what the 4stHEAD software does is to permit the designer to ensure that what is being simulated is possible to manufacture and is practical to use...ie the valves will fit in the head, the springs will permit the valves to function correctly within known stress limits, the loads and stresses and oil film thickness on the cam lobes will permit them to function durably, that the valves lift over the designed duration to the best possible envelope characteristics, that the valve and ports have the correct time-areas for blowdown, pumping, and overlap to be in the ball park to produce the required power at the required engine speed, and to be able to manufacture that cam with software output that a cam grinder can use to produce the designed camshaft that goes inside the cylinder head.


Posted by: gblair

to Cujet
Eric Gorr has already answered the question from a practical standpoint...but there is no reason why any set of valves, ports and ducts cannot flow well and produce decent tumble characteristics for good combustion and fuel preparation. The problem for the tuner is that the more holes in the head, say three for intake rather than two (eg one has the equivalent problem with 2-stroke multi-port scavenging) the more difficult it becomes to get good flow characteriistics into and through the ports and on into and within the cylinder..hence a 5 valve head is more difficult to optimise than a four-valve head for good intake inflow characteristics.


Posted by: EricGorr

In order to make this thread broader in understanding, I’m going to do some moderator’s tasks here and familiarize everyone with current technology and products that are relevant to this thread.

Professor Blair pioneered the development of engine component design software and engine performance simulators. This process started when researchers bolted-up pressure sensors to engine components, from the tip of the air bell to the end of the tail pipe. They reasoned that monitoring pressure in accordance with crankshaft angle. Other sensors were added to segment time and measure temperatures. All of this has evolved through a number of technical papers into baseline standards for dimensions of things like pipes, ports, valves, etc. By using this technology on an accurate dynamometer (not a Dynojet like you see in the magazines but rather a laboratory type setting that has 100% air control), Professor Blair and the researchers at universities like QUB and American companies like Optimum Power Technologies have refined a series of software products and the top of the line simulator is branded “Virtual” with two different programs for four-stroke and two-stroke engines.

Here is a simple chronology of how GP Blair, QUB, and Optimum software has affected the motorcycle/snowmobile markets.

In 1991 the SAE marketed a GPB book and DOS software set titled “The Basic Design of Two-Stroke Engines” A total of 27 individual programs with the source code were included in the set and it all sold for about $150 The programs were quite innovative and some expansion chamber manufacturing companies still use the plotting program, whereby you design a pipe with the software and send it to a plotter to trace paper panels or directly to a machine tool to cut sheet metal. There was also two basic engine simulator programs that provided pressure trace vs. crankshaft angle graphs, and other helpful information like BMEP, HP, peak temperature, in short way more diagnostic information than you can get from the average dyno.

Commercial companies like TSR adapted the code from the book to come up with a variety of programs that have penetrated the tuning market.

In 1996 the SAE marketed the next GPB book titled “Design and Simulation of Two-Stroke Engines” with an optional software package consisting of a single cylinder, reed valve engine simulator. The book sells for about $90 and the software is $500
In 1998 GPB teamed up with Optimum Power Technologies in Bridgeville Pennsylvania to develop a high-end engine simulator intended for the OEM, aftermarket, and academic markets. The packages sell for $12,000/yr lease. A bit pricey for us backyard tuners but reasonable and essential for OEMs that develop performance engines and aftermarket manufacturers on tight time schedules for developing new products.

In 2001 GPB teamed up with Hans Herman, a famous automotive racing engine builder to come up with this new series of four-stroke component design and simulation tools that are designed to work in concert with Virtual Four-Stroke. Basically it’s a combination of mechanical event simulation like you’d find in a high end CAD program, and design parameters that insure that what you’re drawing will actually work on an engine. These are the products that we’ll be discussing in GPB’s software demo on Dec.8th.

Overall GPB’s influence on the development of two-stroke dirt bike engines has been far reaching. Super Hunky first introduced Rich Rohrich and me to GPB’s work in an article in Dirt Bike magazine, circa 1973. GPB and the Queen’s University of Belfast tuned a Greeves 360 As a high school student with a dismal academic record, I was really excited about the concept of a university where their school sport was motorcycle racing and professors hopped-up motorcycles for school projects. In that era, four-stroke dirt bikes were still strong performers and two-strokes were just coming into their own because they didn’t have a big advantage in power to weight ratios and the powerbands were quite narrow and difficult to ride. Eventually GPB & QUB built a long term relationship with Yamaha and many of their joint research projects turned into product innovations on Yamaha motorcycles, then were eventually adapted by other motorcycle and snowmobile manufacturers and aftermarket accessory manufacturers. Rich and I followed GPB & QUB through the SAE Society of Automotive Engineers. We purchase technical papers and books, and try to trace engineering influences in the motorcycle industry and try to imagine how certain research papers will translate into product innovations. So when you look at late model dirt bikes and see things like reed valves, power valves & resonators, outside air bleeds, exotic port designs, exhaust manifolds with anti-reversion mods, and digital ignition maps, you can be sure that many of these innovations were tested in QUB labs by researchers working under the direction of Professor Blair.

Regarding the Virtual Two-Stroke software package, you can check it out online at
http://www.optimum-power.com/main.htm

And if you’re an engine technology maven you owe it to yourself to take in a demo of the program at a tradeshow where the folks at Optimum display their goods. They’ll probably have a listing on their site but the one place that comes to mind is at the SAE show in Detroit’s Cobo Hall in the middle of January. Virtual is a Windows based program relatively easy to enter data and run simulations upon.


Posted by: cujet

I am sorry I cannot attend! I looked over the site and did not see any 5 valve software, did I miss it? Eric Gorr and gblair, although I am not involved in manufacturing I regularly build engines to very high states of tune. I have a background in turbocharged race cars and fabrication experience. I am one of those guys who designs and builds jet engines with afterburners for various non aviation uses.

gblair, I guess what I meant to ask was, if I were to convert a modern dirt bike 4 stroke engine by way of modification to a straight shot intake port design, would it be worth the effort. I had in mind the CRF450 or YZ/WR450F. My goal has always been to have a lightweight dirt bike with 70 or 80 HP. What I see going on today, the loss of the big bore 2 stroke, leaves me with fewer options. I had always hoped for a modern CR500 with a powervalve and a counterbalancer. Now I am thinking along the lines of a big bore 4 stroke. However bikes like the XR650 are so overweight, and underpowered in stock form.

Chris


Posted by: gblair

to Eric Gorr
...actually the starting point of the work on the 4-stroke cylinder head component design software (4stHEAD) goes back much further than 2001..but that is really only a detail..I offer it only to put the extent of the effort into the correct context.


Posted by: gblair

to cujet
...no you did not miss it...there is no specific 5-valve software in the suite at this moment in time as the number of manufacturers of 5-valve engines is limited and the 2-valve and 4-valve head makers are legion.

..as to designing and making your own head/valves/camshafts then why not but it is not as inexpensive an exercise as doing one for a 2-stroke. As to the straight-shot intake port (as you put it) then E Gorr has already pointed out the packaging problem for you for that engine...and in truth I do not think that the total effort in terms of extra power would be really worth the packaging problems that are entailed on an off-road motorcycle.


Posted by: Ol'89r

Professor Blair.

Welcome to DRN. Thank you for sharing your knowledge with us. Coming from an age where we used degree wheels, dial indicators, clay and a whole lot of trial and error for these kinds of things, I am very enthusiastic about learning more about your programs.

Is there a possibility that you may attend any of the trade shows on the West coast?

We have a pretty knowledgeable group here on DRN and we love to talk shop. Now, this is simply the icing on the cake. :thumb:

Ol'89r


Posted by: gblair

to Ol'89r..
..no plans to go to the West Coast..but I will be in Indianapolis for the SAE MotorSports Engineering Conference next week and also (for 1 day) at the PRI Show....and thence to work in Charlotte NC for a day or two and then golf for a day or two at Myrtle Beach.. before returning to the rain and wind in Ireland on December 17.....so..gentlemen any questions you have need not be posted after December 1 until December 17...that should give you lots of time to think of something difficult...


Posted by: gblair

..oh..and I nearly forgot..to be in WI to meet Mr Gorr and 'friends'!


Posted by: nephron

Professor, your presence is humbling and very much appreciated.

This may be an ignorant and useless question, but what do you think of John B. Heywood? Have you had much interaction with him? My dad, who's a hell of a lot smarter than I am, stole his book from me (Internal Combustion Engine Fundamentals) and went on the lamb. Just curious.

FWIW, you'll need to learn the art of ignoring a certain number of these questions, or the 'ol self-fulfilling prophecy of "excellence begets many questions, and the many questions begets fatigue" (er, you know what I mean :o ).

Best wishes,

Jack


Posted by: gblair

to nephron
...I cannot possibly respond to queries as to 'what do I think of X' as a person, as an engineer, as a racer, or as whatever, so I will simply say..'pass'...and will naturally do so to all such questions....as I am sure you will understand.


Posted by: Swiss

Dr. Blair,
Welcome to the forum. There are 4-stroke tuners on the forum, I just cranked into this post. It is always a problem when you are dealing with someone that has years of comprehensive research into a specific subject to come up with seemingly intelligent questions. I have been looking at purchasing copies of your book and software over the last few years, but have wondered about the cost versus tuning benefits. Most of us can get to modifying various Factory engines, but not to the level or cost as you mentioned earlier of actually designing or building an engine or even just a cylinder head from scratch. We end up modifying various Factory engine designs in search for more or better power while keeping the various mods from self destructing.
Had I gotten your book and software in the past it would probably be easier to post more specific questions on various topics. I have always believed in working with a "complete" engine, in other words, you don't "JUST" add a cam or an aftermarket pipe and expect to achieve the potential of the engine design. I understand that the factories have a LOT of different restrictions on their designs and I have to laugh when someone comes up with the attitude that "Honda" engineers (or others) are so smart that they don't make mistakes or aren't limited by budgets. Or the idea that this or that exhaust system design or cylinder head design is the ultimate for a given engine, when they turn around and change it the following year to something much different. A lot of it is marketing and sales. And of course, the rantings of magazine guys who repeat miss-information that they have gotten from various "Tech" people in the industry. The "typical" exhaust system Dyno Shootout is a good example. 10 different systems with minor and major differences in them, but rarely is a negative word spoken within the test. The conclusion often doesn't match the test data and the results can easily be questioned. A few years ago one of the Dirt bike mags (DB or DR) published a set of dyno tests for systems for the 400 Yamaha. They tested about 11 systems and rated them both on the dyno and at the track. The ONLY changes that they made were the exhaust systems. First of all, the small (hard to read) dyno charts were all done individually, and not overlaid so that direct comparisons could be done. Then they had their rpm lines done wrong and other errors. With a lot of work, I figured out how to correct their problems. One of the pipes showed a clear benefit over all of the others in the dyno testing. Strong low-end, building into a hard hitting mid-range and then making as much top end as any other pipe in the shoot-out.
On the track the testers said that this pipe didn't give much of a power increase in the low end, was hard to ride and pulled too fast into the top. They ended up rating the pipe as about 7th or 8th out of 11 or so systems. This "testing" didn't adjust the rest of the bike to take advantage of the increased performance of the pipe. Things like gearing/tires/suspension changes and overall tuning might have placed the pipe at the top of the ratings, but the riders at the Track were thinking that the pipe was soft at low rpms because it actually hit so hard and pulled strong into the mid and upper rpms. So they rated it hard to ride.
I guess that part of the problems with the magazines is separating the crap from the intelligent information. The "results" from the marketing hype! I still like reading the various tests, but I recognise the "bolt-on" philosophy as a limited way to increase performance.
I wish that I could make it to your "demo", but it is a LONG ways from New Mexico!! I think that as far as getting some specific questions and threads going it is kind of tough, Since I am sure that you have worked with the 5-v Yamaha engines, you might give some comment on the general benefits of 2-v/4-v/5-v head designs. Also some comment might be given about port velocity vs. power output and powerband since there are a LOT of different views about how much velocity is needed for performance and what the eeffcts are on the powerband. Such as if you have small ports and high velocity, what kind of limits are put on the engine for upper rpm performance. It seems sometimes that the larger carbs work well with the 4-stroke engines because of decreased flow resistance, rather than as a result of required air flow through the carb/intake.
Comments on the rpm/piston speed levels of the new Vance and Hines drag bike? Giving supposed piston speeds of about 7,000 fpm?

Maybe this will help to get some discussions going.

Swiss


Posted by: Swiss

Dr. Blair,
Thinking about it, I came up with a couple of specific questions, one for intake tuning and one for exhaust tuning. Both of them concern conical effects on airflow and pulse tuning. Second question will follow this post.

Intake first, when tuning for the various pulse tuning harmonic lengths, what kind of effect would having the 2nd, 3rd and 4th harmonic lengths all tuned for the same rpm. Such as the carb venturi tuned for the 4th, and the end of the bellmouth for the 3rd and a concave airbox (shape focused on the venturi center) at the 2nd harmonic length? Going beyond this, will the shape and length of the carb intake bellmouth affect the powerband similar to the benefits of a megaphone in the exhaust system, in other words, tuning across a wider powerband than an abrupt open end to the carb at the airbox?

Thanks,
Swiss


Posted by: Swiss

Exhaust question.

For the exhaust, I know that the megaphone design positively affects the powerband (IF the design is right), but I have never been able to find any data about the technical data about reverse cones on megaphones. I know that they are needed, but don't have any specifics about how their taper angle and outlet diameter relative to the max megaphone dia. will alter the powerband. I am aware that multiple angles in the primary cone can have effects on different points in the powerband, and that dyno tuning could be done to find gaps or negative regions that can then be affected by exhaust design.
The real question is can a multiple angle reverse cone also be used and to what effect? What general effects do the outlet diameter and the angle have on the power maximum or powerband?

You asked for questions,
Swiss


Posted by: gblair

to Swiss..
you probably will think this is the con to end all cons...but do please buy that SAE reference R-186 textbook of mine and you will get 99% of your questions answered....and after you have read it and you still feel that you have been conned then do ask again...
..the blunt answer to many of your questions are not such as can be answered with simplicity..only a good engine simulation can sort out what is happening in what position in what duct and its effect on the all-important cylinder flow so that I cannot answer you totally directly except to say that my book is full of empirical guidance on many of the very topics that you raise..and clearly I cannot repeat 813 pages worth here in this small space!
..specifically..and in general only the length of a bellmouth will affect the power band and the engine speed for optimum intake ramming unless it is VERY steeply tapered (ie >0.2 mm/mm) in which case there would be modest (increase) of length dimension to achieve the same effect..but it is really the total length from the intake valve seat to the end of the bellmouth which is the effective tuning length.


Posted by: gblair

to Swiss
I have never seen a multiple-angle reverse cone on a four-stroke exhaust megaphone and I have never simulated an engine with one on it so I cannot answer your question.


Posted by: gblair

...and to all you gentlemen..
..it is now 7 pm here in Belfast and I have to go pack a bag to go to the airport to catch a plane to Indianapolis...back again (I hope) on December 17.....so all new questions will remain unanswered until then!


Posted by: Rich Rohrich

Quote:
Originally posted by gblair
to Swiss..
you probably will think this is the con to end all cons...but do please buy that SAE reference R-186 textbook of mine and you will get 99% of your questions answered....and after you have read it and you still feel that you have been conned then do ask again...
..


I can attest to the value of Prof Blair's book Design and Simulation of Four-Stroke Engines SAE #R-186. It goes into great detail from an engine designer's perspective with an eye towards using the accumulated knowledge to make better use of engine modeling as a design tool. It differs from most books of this type by including something that is usually shunned by academics. Included is a large (~80 page) chapter called Empirical Assistance for the Designer of Four-Stroke Engines. This chapter is essentially case study information on a host of deadly serious engine designs including a Nissan IRL engine, Ducati 955, Mathchless G50, F1 and ITC race engines among others.

This adds a lot of valuable information that is usually hidden from those of us who don't get the chance to see the inner sanctum of high-level professional engine builders. It makes for an excellent balance to the engineering theory based portions of the book, and it makes it easier to grasp the basics of using advanced simulation software .


Posted by: IrishEKU

Quote:
Originally posted by gblair
...and to all you gentlemen..
..it is now 7 pm here in Belfast and I have to go pack a bag to go to the airport to catch a plane to Indianapolis...


Professor, have a safe trip and I look forward to hearing how the seminar went.

Thanks for coming to DRN,


Posted by: EricGorr

Just to give you guys an update on Professor Blair's software demo,
I booked a conference room at the Holiday Inn in Fond du Lac Wisconsin with a large screen and projector so we can all see the demo properly. The date is December 8th starting at noon. Enter the lobby and look for the conference room titled "Professor Blair's Software Demo".
I've invited some local Winston Cup engine builders, snowmobile tuners, and an eclectic mix of mechanical engineers interested in motorcycles. I'm looking forward to learning from the interesting discussions that we're likely to have.

Have a safe trip Professor Blair and I hope the weather is warm and sunny on the golf courses of the Carolinas :thumb:


Posted by: SFO

I wish I could attend the 'Scony convention. :whiner: :whiner: :whiner:
One 5V question would be, what about having muliple profiles on your intake cam to manipulate flow and tumble in addition to different valve diameters on the intake side?
AND
Would it be possible to move a valve too quickly and create a cavitation of the airflow behind it, or is the pulse too strong on the backside of the valve face to allow this to happen?
Are we anywhere close to this valve speed or is this the land of pneumatic or solenoid valve actuation?


Posted by: nephron

Quote:
Originally posted by gblair
to nephron
...I cannot possibly respond to queries as to 'what do I think of X' as a person, as an engineer, as a racer, or as whatever, so I will simply say..'pass'...and will naturally do so to all such questions....as I am sure you will understand.


THAT bad, eh? :scream:

As regards my original point of not responding to all questions, looks like you've started with mine.  :thumb:

 


Posted by: 400sxman

hi, i was wondering if you could respond to the "reciprocating mass" post? i'm sure a person of your caliber could settle this thing once and for all with a definative answer. thanks a lot
~Nat


Posted by: EricGorr

400sxman
I think that one of Professor Blair's colleagues Charlie McC responded with a definitive answer to your post on the reciprocating mass. It may not of been what you wanted to hear but it makes sense to me. Theres no magic bullet out there.


Posted by: 400sxman

oh, ok, the problem with the internet is you never know who knows what there talking about, good to know that theres now a definative answer. its not that i won't believe it if i don't like it, its just i don't know who to believe. thats why i asked you in the first place (lol, i didn't understand your answer though ). thanks
~Nat


Posted by: 400sxman

eric, by the way, the kettering university formula SAE engine team may be present, i won't know till the meeting on wednesday


Posted by: EricGorr

Thats great! The more the merrier. We'll just move out of the conference room and into the Tiki bar in the Holidome.
One late edition, Gary Gilbertson hydroforms tapered header pipes and megaphones, he's bringing some samples for us to check out. Funny enough his workshop is only a block away from the Holiday Inn.
This is gonna be so cool :thumb:


Posted by: 400sxman

it was brought up at the team meeting today and every oen wanted to go, unfortunatly, with the term winding down theres exams coming up for all of us on monday and none of us can make it. i'm sorry to miss it, it should have been interesting.


Posted by: bedell99

I was wondering if Professor Blair is still writing SAE papers on "two" stroke tuning. Very informative website. Thank you very much.

Erik


Posted by: SFO

Any update on the PRI show or the BLAIR fourstroke witchcraft seminar?
See y'all at the next superflow seminar...


Posted by: EricGorr

SFO,

A group of 15 lucky gearheads spent 4 hours running through demo simulations of Professor Blair's new component design modules for 4-stroke engines plus a sampling of 2&4-stroke simulations of Optimum's Virtual engine simulators. Incredible stuff! The Professor gave us hundreds of tips on designing engines along with some humorous anecdotes and some excellent racing stories from Ireland.

The software itself stands alone and works well as a plug-in to Virtual 4-Stroke. And the price is very reasonable. For the modules pertaining to cylinder heads, camshafts, and springs its only $6,000 for the set, no license fees or leases, just a 1-time purchase. Theres a German company selling a competing product for $30,000 and it doesn't do half what GPB's software does. Considering the high cost of developing products in the motorcycle aftermarket, GPB's software has quick payback time. I saw a lot of potential for using the software as diagnostic tool for tracing OEM engine failures. Especially ones involving premature intake valve wear on CRFs and catastrophic valve train failures on KTM 400/520s.

When the Professor showed us a 3D flow map of a 5-valve YZF head Rich and I just looked at each other and conversed telepathically about his ealier post about why the 3 valve intake port is so unstable compared to a traditional 4 valve head. It all made sense in an instant and it really scares me to think that guys are out there porting those heads with wild abandon. I'm sure Rich will have some good posts on that subject in the near future.

The 15 people who attended the presentation included some individuals that made the discussion that much more interesting. After 4 hours of staring at formulas, mass flow rates and animated waves in super-position you'd think people would be tired, but we all left the presentation more revved up than a group of kids gorging on Halloween candy!
I think that we have enough material from this one presentation to nurture this forum through the winter.

I'll go out on a limb and say that within a year the state of art in off-road motorcycle aftermarket accessories will be greatly influenced by Professor Blair's software. If the mainstream west coast companies check it out I'm sure they'll realize its something that they can't afford to be without.


Posted by: SFO

Quote:
Originally posted by EricGorr
SFO,


When the Professor showed us a 3D flow map of a 5-valve YZF head Rich and I just looked at each other and conversed telepathically about his ealier post about why the 3 valve intake port is so unstable compared to a traditional 4 valve head. It all made sense in an instant and it really scares me to think that guys are out there porting those heads with wild abandon. I'm sure Rich will have some good posts on that subject in the near future.


I remember a Krause editorial from the '80's regarding a G code interpretation of a stationary paletiser(sp?).
I can only imagine a sublime engine conversation with you guys...


Maybe DW, '03?

Did you talk to Mike Perry?


Posted by: IrishEKU

Quote:
Originally posted by EricGorr


The 15 people who attended the presentation included some individuals that made the discussion that much more interesting. After 4 hours of staring at formulas, mass flow rates and animated waves in super-position you'd think people would be tired, but we all left the presentation more revved up than a group of kids gorging on Halloween candy!
I think that we have enough material from this one presentation to nurture this forum through the winter.

I'll go out on a limb and say that within a year the state of art in off-road motorcycle aftermarket accessories will be greatly influenced by Professor Blair's software. If the mainstream west coast companies check it out I'm sure they'll realize its something that they can't afford to be without.


Eric,

I am really looking forward to reading excerpts of your experiance and RR's under the direction or Prof. Blair's tutelidge. Not to mention his input!

Granted I am working with a couple of stock strokers, I'm sure I can show their owners "The writing on the wall" with your help.

Thanks Eric!


Posted by: Daniniowa

The presentation was really great. I know I didn't get nearly as much out of it as Rich or Eric, but it was still completely awesome. I do have enough college behind me to understand some of the mentions of Moody number when referring to surface roughnesses, Reynold's number when refering to flow, and a few others, but the Virtual 4-Stroke software still seemed easy to use. The 4 Stroke Head software that Professor Blair is selling definately has it's purpose clearly defined and does a great job of it. Watching the spring analysis was very informative. I had no idea that the valve springs have an increasing load, from top to base. It really makes one wonder how much better a progressive rate spring would work. Maybe a spring with a continually increasing diameter to account for the increase in load.

I didn't understand the 3-D flow diagrams, so if Eric or Rich could explain them, I'd be really greatful.

I can't wait for our Virtual 4-Stroke software to arrive. I am a little concerned with how long it will take us to measure everything we need to be able to simulate our engine for our Formula car, along with how long it will take us to learn how to use the software.


Posted by: EricGorr

Dan, glad you could take time from your finals schedule and drive 5 hours for the presentation. I'm a bit embarrassed that none of the team members from the two teams at UW could drive only an hour to see the Professor.
Taking the measurements from an engine isn't that difficult but you'll need a good dial caliper and an inside divider so you can measure the port diameters at different depths. The surface area of the cylinder head can be measured by wetting a peice of 1 sq/mm graph paper and conforming it to the inside of the head, then counting the squares. Rich and I have a Cam Doctor to measure cam lobes. Its a linear encoder and a dial stand. They sell for about $3000. The part that befuddles me is mapping the flow coefficents of the ports. The apparatus that QUB uses is basically a 500 gallon vessel of compressed air that is carefully dumped through a cylinder head to simulate the velocity at the valve, which is way higher than anything that we can staticly simulate on a flow bench test where the valve is set at 5 test points and a mere 10 inches of water pressure is applied. The Professor really drilled that point home. The simulators in the $500-1000 range use data from a Superflow flow bench. Having an accurate port flow map is really the key to an accurate simulation.
Perhaps there is an undergraduate student at QUB that runs this apparatus on a regular basis. Who knows, maybe he has mapped a head like the one you guys use in your SAE car. I know one thing, I'd like to get them to test a slew of YZF heads because I don't think any tuner in this country has a clue as to what makes that thing tick.

SFO - Thanks for introducing us to Mike Perry. He was real helpfull, sounds like he has a similar background as us, a blue collar engineer. I hope his schedule at Kibblewhite frees him up enough to do some of his projects.
We had a good chat with Bob from Cometic on the subject of YZF head gasket failures. They're making a new style head gasket with a layer of quarter-hard stainless steel in the center, and he liked Rich's ideaof replacing the head bolts with studs. We also met a guy from Florida who makes adjustable ignition systems, he was hanging out in the Cometic booth with us.
The machine tool hall was awesome. More later.


Posted by: SFO

Quote:
Originally posted by EricGorr
he liked Rich's ideaof replacing the head bolts with studs


That will probably make top end removal a motor out deal, not that I'd mind...


Posted by: farmboyrr

I truely feel sorry for the engine builds and designers that didn't make it to Professor Blairs' presentation. The infomation he presented was inspiring. I concidered myself lucky to have been able to attend, being just one of the many gearheads that is sometimes overwhelmed by the black arts. I hated to leave the dinner we had with the Professor. I could have listed to his stories for hours. I'm Eric feeling the same.
Thanks again to Professor Blair.


Posted by: IcerDave

I too would like to thank Eric and Proffessor Blair for their time and hospitality. For the short time I was able to attend prior to my leaving for a previous engagement (thanks brett;-) it was an honor to sit in and listen and attempt to comprehend this incredible program. Luckily my two smarter cohorts were able to stay for the duartion. It was also nice to meet a few other influential ppl here.

Thanks Again!

Davestillthawingoutfromlastnight:-)


Posted by: Swiss

Guys,
The easiest way to get the correct port dimensions is to use the port with the valve installed as a mold and fill it with some of the rubber type of molding materials that are available. Use a slick release coating on the port walls and valve stem. Slit the rubber after it sets, in a line up to the valve guides so that the rubber can be pulled out of the port. You then have a 3-dimensional part that can be measured and later compared to your mold of the ported head.

Swiss


Posted by: Rich Rohrich

The newer molding compounds allow you to cold set mold a port in under 15 minutes and remove it intact without using release agents or sliting the mold. I brought some samples of CRF port molds to the Blair conference to show the guys.


Posted by: Lobster

I finally get around to reading this thread, and I find out Professor Blair was in town.......last Saturday, I live in FDL! Crap. I remember one of my instructors used to mention his(your) name during lectures and almost call for a brief moment of silent reverence.

I'm sorry I missed out on such a great oppertunity.


Posted by: gblair

to Lobster
sorry I was in Fond-du-Lac and you didn't know about the talk I gave....too bad....maybe Eric will schedule another when next I visit...but who knows when the wind blows in bad pennies if you will excuse the mixed metaphor!


Posted by: gblair

to all who came to Fond-du-Lac...
I found it pretty humbling to discover that so many came from so far just to hear what I had to say....or maybe to find out what an Irish motorcycle racing engineer/Professor actually looked like! Either way I truly enjoyed the experience and much thanks from me must go to Eric Gorr for organising it....


Posted by: gblair

to bedell99..
yes, I published a paper along with Mr Gustafsson of Husqvarna (chainsaws in Sweden) at the SAE/SETC meeting in Pisa last year (November) on the use of a very, very, compact tuned system for a 2-stroke leaf-blower engine which improved the power by some 10% but brought the fuel consumption down by some 30% and the unburned hydrocarbon emissions down by a factor of 4 so that it could meet EPA emissions legislation without a catalysts yet still using a simple carburetter.


Posted by: gblair

to daniniowa...
...regarding the Cd diagrams (the 3D diagrams you refer to) they are described in great detail in my (SAE R-186) textbook where a full chapter is devoted to such a topic and many such diagrams are displayed and explained.


Posted by: gblair

to Eric Gorr..
..the tank used at Queen's University for the suction of air through the valves and cylinder of the engine is more like 20,000 gallons in volume and can be evacuated to about 14 psi below atmospheric pressure...hence the ability to measure flows across the valves at a 2:1 pressure ratio and the Cd values that accompany it..and then map them as a (Cd-pressure ratio-valve lift) function of both pressure ratio and valve lift as I showed at the FDL meeting or in that (SAE R-186) textbook.


Posted by: gblair

to Swiss...
I must repeat that most of the answers to your questions are to be found in that (expensive?) SAE R-186 textbook and in response to that I would venture to suggest that you probably spend more on those magazines that you deplore for giving you misleading information than the purchase price of this (so-called expensive) book.
In direct answer to your question...I ma not at all familiar with the Vance and Hines drag bike so I really cannot help you there...except to say that in the world I live in about 5000 to 5100 ft/min is very widely regarded as the current piston speed limit..but maybe if you only run for 5 or 6 seconds on a drag strip that could be exceeded.


Posted by: Daniniowa

Our FSAE Virtual 4-stroke software is installed and running, and I now have the book. I will assume, that through reading (and rereading) my understanding of engines will grow quite a bit during the next couple months (and probably fustration at times) before going to competition. 3 semesters of school left, and I look forward to the learning.


Posted by: Rich Rohrich

Quote:
Originally posted by gblair
to all who came to Fond-du-Lac...
I found it pretty humbling


... as did most of us Professor Blair


Posted by: Swiss

Prof. Blair,
I do intend to get a copy of your book. One question that I have at this time is about valve sizes for a given bore. Comparing a 2-v head with a 4-v head, in relation to the bore size is there a set of ratios for the 2-v head and the 4-v head to find the maximum valve sizes for the bore? What kind of typical flow increase can be shown for a 4-v head over a similar 2-v head. Yes, I understand that much of the flow difference is shown in the lower lift range of the 4-valve head, and that the valve angle and lift will also limit the possible sizes of the valves due to their interferance at overlap. I remember in one of those early CAR magazines they were looking at the 4-v heads for one of the Americal V-8 engines (prototype aftermarket stuff) and they gave a so called optimum ration for valve diameters for both 2 and 4-v heads. Can't find that information right now.

Thanks,
Swiss


Posted by: gblair

to Swiss..
..with the valve size ratio, Kie, defined as the ratio of the inner seat diameter (on the valve seat) of the intake divided by that of the exhaust, then the applicable valve size ratio used for either 2v or 4v or even 5v engines is on the order of 1.1 to 1.2. Naturally, for multiple intake or exhaust valves one multiplies the relevant valve seat diameter by the number of those valves (for 2v and 4v the 2 and the 4 multiplier cancels out ot course, but not for 3v and 5v engines). I tend to start a design with about 1.15 for Kie.
..as to flow rate through a valve the maximum flow rate is always around the maximum lift region and so it is in the maximum lift area that the 4v design beats the 2v engine.
...as to the difference in flow rate between 2v and 4v engines of (say) equal design merit, typically a 4v engine will flow some 10-15% more than a 2v engine in terms of delivery ratio (or volumetric efficiencey if you prefer it) and the disparity tends to increase towards the highest engine speeds.
...actually valve interference during valve overlap is only a design concern for 2v hemi-head designs with a large included valve angle (say 30 deg or more) and is rarely a mechanical design problem on 2v wedge head designs (but only if properly designed) or a 4v pentroof design.


Posted by: gblair

to Daniniowa..
I am delighted to hear that you are about to use the Virtual Engines software...good work...


Posted by: gblair

to Mr Rohrich...
thank you for the kind comment...
..mind you the Gordon Jennings quote underneath could be misinterpreted...i.e., am I one of those old go-fast guys referred to with no wrinkles on the inside? (I will confess to lots of wrinkles on the OUTSIDE at the corners of the eyes though and at my age one would expect little else!)


Posted by: gblair

to all...
...I do not understand the clock on these pages...it now says that the time is GMT (is that Greenwich mean time + 13 hours) and that it is 5.16 am in the morning which is indeed correct as it it is now 4.16 pm UK time or GMT. But why is the clock set to that peculiar time?


Posted by: gblair

..I am not really expecting a reply as I have posted about six comments above on the 23 December 2002 and not a response to any of them yet this is the 4th day of January 2003!


Posted by: marcusgunby

Prof blair i have some questions but they are 2 stroke in origin-onto your clock, you have to set you local time in 'your cp' at the top ofd the page, i had a weird issue where it was a few hours out even when set to GMT London-i found out the PCs internal clock has to sychnonise with the net every so often.Mine couldnt find a clock and couldnt schycronise.Its all ok now(i hope)


Posted by: Rich Rohrich

Quote:
Originally posted by gblair
to Mr Rohrich...
thank you for the kind comment...
..mind you the Gordon Jennings quote underneath could be misinterpreted...i.e., am I one of those old go-fast guys referred to with no wrinkles on the inside?


Professor, after meeting you and seeing the enthusiasm you still bring to even a simple get together it's clear to me at least that you ARE one of those old go-fast guys with no wrinkles on the inside :thumb:

Rumor has it that you and the late Mr. Jennings had some spirited discussions about the Isle of Man TT on more than one occasion.


Posted by: Ol'89r

Quote:
Originally posted by gblair
to all...
...I do not understand the clock on these pages...



Somehow, I knew Marcus would answer this one. :thumb:


Posted by: marcusgunby

So far i have been beaten by KTM suspension and CR engines but a silly clock wasnt going to win


Posted by: bclapham

well i dont know what my clock is saying, but by my estimations its about time for a cup of tea!


Posted by: gblair

to Rich Rohrich....
it is interesting how 'slang' is different on the two sides of the 'pond'. A 'wrinkle on the inside' in British slang would be 'a useful tip constituting significant inside knowledge'

..as to the late Gordon Jennings..I always enjoyed reading his articles in the several forums in which he wrote although along with several other technical writers of his ilk I did not always agree with the tuning concluions to which he came. Mind you, and in ammelioration of that opinion, most of Jennings generation did not have the benefit of the 'hindsight' which many of us acquired after some 30 odd years labouring in laboratories! As I recall, I only met him in person once.


Posted by: gblair

...to all you clever people who have helped my clock to tell the correct time..thanks!


Posted by: gblair

to Mr Gunby...
...if you wish to ask a question on 2-stroke ports then please do it in the forum 'porting and flow', where you may be interested I have already posted a 2-stroke porting tip (wrinkle to Mr Rohrich!) for those still tuning that engine which the FIM seems keen to eliminate from the world of motorcycles.


Posted by: gblair

to Mr Rohrich..
...please forgive the poor typing of the words 'conclusions' and 'amelioration' in my last reply to you.


Posted by: Rich Rohrich

Quote:
Originally posted by gblair
to Mr Rohrich..
...please forgive the poor typing of the words 'conclusions' and 'amelioration' in my last reply to you.


No problem :thumb:


Posted by: tightwoods

Great stuff, Dr. Blair!  Interesting and exciting.

tightwoods


Posted by: gblair

..things have gone very quite in here..is all technical curiosity now satisfied?


Posted by: cujet

Not even close

Chris


Posted by: cujet

gblair, I am interested in tuning a 450cc cylinder's intake manifold to 6000RPM on a fuel injected engine. Do you have any suggestions as to diameter and length? Should I stick with OEM port diameter, or go to an optimum size? Would you be willing to share your favorite method for finding the proper tuned length? I have general formula's that have been floating around in my tool box for 20 years. It seems to me that modern experience with high performance 4 strokes may have enlarged the knoledge base on this subject.

TIA,

Chris


Posted by: Rich Rohrich

Quote:
Originally posted by cujet
Would you be willing to share your favorite method for finding the proper tuned length?


The good professor has already done that, AND THEN SOME in his book :thumb:

Design and Simulation of Four-Stroke Engines AUTHOR: Gordon P. Blair

This book provides design assistance with the actual mechanical design of an engine in which the gas dynamics, fluid mechanics, thermodynamics, and combustion have been optimized so as to provide the required performance characteristics such as power, torque, fuel consumption, or noise emission. Many engines (including a number of famous ones) are used as design examples and analyzed.

http://www.amazon.com/exec/obidos/t...=glance&s=books


Posted by: gblair

to cujet...

.as Mr Rohrich has already indicated..but here is more detail...

re intake manifild tuning I have devoted many pages in a book to this topic...formulas and all...so it is all there in black and white...on pages 652-671 inclusive!

http://www.sae.org/servlets/product...ON_SUCCESS=TRUE


Posted by: gblair

to all ..

...it is still very quiet in here...I am beginning to suspect that the users of the new 4-stroke dirt bikes are more loath to partake in 'hands-on tuning' than in the '2-stroke' days when a bit of filing at the ports produced instant and different (you will note I did not say better!)performance characteristics whereas the same 'tuning' approach on a 4-stroke engine has to be conducted in a different and, possibly, a more expensive manner. Any views on those thoughts?


Posted by: luvtolean

Quote:
Originally posted by gblair
to all ..

...it is still very quiet in here...I am beginning to suspect that the users of the new 4-stroke dirt bikes are more loath to partake in 'hands-on tuning' than in the '2-stroke' days when a bit of filing at the ports produced instant and different (you will note I did not say better!)performance characteristics whereas the same 'tuning' approach on a 4-stroke engine has to be conducted in a different and, possibly, a more expensive manner. Any views on those thoughts?


I think you are onto something. To port a 4 stroke head, you must disassemble the valvetrain which requires special tools and/or more money. I never ported my roadrace bike because is was so expensive and the results so unknown(I tried cams and they didn't add any real HP, just altered the HP curve), so I didn't go for it.


Posted by: luvtolean

OK, I have a question. A while back a friend and I were talking about airflow in a cylinder head and I recalled a golf ball problem I did in Fluid dynamics class. We had to calculate the distance a golf ball would go if it was smooth based on the distance it went dimpled. It was a huge difference, with the smooth obviously going a much shorter distance.

So my question is, do you Gblair or anyone else have experience with the flow and power characteristics of a head ported like this?


Posted by: gblair

to LuvToLean...

..the problem is not quite the same...flow in an engine is contained internal flow in a duct.....and if the intake duct shape had a dimpled surface and an identical shape with a mirror finish the upshot in flow terms would be a marginally higher air mass flow rate at the same overall pressure ratio for the one with the mirror finish due to the reduced friction of the mirror finished duct. However, the polishing of the (dimpled as cast) finish of the intake duct permits the 'smoother person' to see and remove bumps and other profile imperfections in the cast shape that would go unnoticed if the finish is left 'as cast' and this tends to improve the airflow.
The golf ball flight problem is different..it is about external flow around a spinning spherical object.....and you will notice that aeroplane wings do not have dimpled but smooth polished surfaces because the flow while also external flow is not around a spinning spherical object and friction reduction all over the surface of the entire device is vital.


Posted by: Ol'89r

Quote:
Originally posted by gblair
to all ..

...it is still very quiet in here...I am beginning to suspect that the users of the new 4-stroke dirt bikes are more loath to partake in 'hands-on tuning' than in the '2-stroke' days when a bit of filing at the ports produced instant and different (you will note I did not say better!)performance characteristics whereas the same 'tuning' approach on a 4-stroke engine has to be conducted in a different and, possibly, a more expensive manner. Any views on those thoughts?


Hi Professor Blair. We're still listening.

My personal views on the subject are, I believe MOST every combination of port design, valve design and angle, cam profile, etc, etc, has already been tried.

I feel the area that will give the modern four stroke its most performance is in engine managment. By taking the power we already have and puting it to the ground. Makeing the power usable. I feel many strides in this area can be made through the use of computor managment. We have already seen this with the ability to re-map the ignition curve in the current 4-strokes.

Modern engines seem to be limited by their own mechanical ability or inability. They are limited by the strength of their internal parts to overcome high RPM's, high head pressures or compression without destroying themselves.

By using a little different technology, such as pneumatic, hydraulic or magnetic actuation for valves we could go beyond this current barrier. Also, new materials could have a big impact in the way an internal combustion engine will perform. Plastics, ceramics, urethanes, not to mention new hardened coatings. How about a plastic engine that weighs about 25 lbs and has no heat transfer problems???

In my own experinence with 4-stroke engines, I have found that the factorys know a lot more than people give them credit for. By changing a port design, seat angle, etc, etc, in a modern 4-stroke engine, more often than not you will cost yourself HP or torque. Small gains can be made , but it is very easy to wind up with something that is un-ridable. In the 60's and 70's we were able to port an engine, change the valve and seat angle, modify the cams and wind up with a better engine. I don't think this is so true anymore.

In the early 70's I was fortunate enough to get to work on the Triumph factory race team. We set up the factory road racers and did the R$D on the road race and dirt track engines. We were able to go to the parts room and get a new part to modify and run on the dyno. We went through a lot of new parts trying to figure out what worked and what didn't. We tried different port designs, valve angles, seat angles, rough ports, smooth ports, tapered ports and induction tracts. Not to mention just about every cam profile configuration you could think of. This is where I first learned that the factory engineers knew their stuff.

How about a design where the cams are adjustable on-the-fly? Where they will automatically advance or retard themselves as needed for the proper torque at the proper time? Or, how about eliminating the cam altogether and using a hydraulic pump and a hydraulically acutated valve, or a rotary valve? This could raise the threshold on RPM's considerably.

How about a hydraulic drive or hydrostatic drive instead of chain drive? How much travel could you have if you didn't have to worry about the drive chain sawing through the swingarm? Two wheel drive?? :scream: Hydraulic traction control?? The possibilities are endless.

I like to keep an eye on the F-1 world because it seems that we are just a few years behind what happens in F-1 They are already trying some of these new technologys in F-1 along with traction control and active suspension. Motorcycles won't be far behind.

These are very exciting times for 4-stroke technology and I feel the best is yet to come. :thumb:


Thank you again for sharing your vast knowledge with us.

Ol'89r


Posted by: gblair

to OL'89R...

..that certainly seemed to stir you into putting 'pen to paper'!

..firstly, there is no doubt that igniton mapping and fuel mapping improves engine performance, and dirtbike engine performance particularly....there I agree with you..
..however, every such change automatically brings the need for differing valve lift profiling (ie cam), intake and exhaust duct tuning to further optimise those fuel and ignition mapping changes...and not all factory engineers are real experts in this area.
...as to the magnetic motor, hydraulic and other valve drive systems, at this juncture most, if not all, are very bulky and some are also engine speed limited...and bulk and weight are death on an off-road bike. While I agree with you that variable valve timing is indeed the tuning key, methods other than mechanical are not yet a racing option.
...as the best route to engine development is through thinking guided by the use of an accurate engine simulation followed by the actual build and dyno test it is quite surprising how much is still conducted in the 'factories' by 'seat of the pants' 'cut and try' methods. The thinking and design culture so prevalent in F1 (as you put it) has not yet permeated all that widely througout the racing industry.


Posted by: techman

Eric, to go back a few posts, referring to the vaccum discharge tank: we used a small version of vaccum extraction for testing a pneumatic servoed system some time ago where we used a water-loss turbine or rotary blade of some sort vaccum pump that could pull a mean vaccum with substantial flow. The water always flowed through the unit and into the drain while it whirred away. We inadvertently made an accumulator of sorts by running the big hose (2" dia I think) up from the basement one floor to a bit of a manifold. We hardly saw a blip in the local vaccum gauge during operation. However, such a system would be limited in duration of sustainable flow to shorter bursts, if the bursts were large flows. But, such a system would be massively more doable and cheaper than a huge vaccum chamber!! One could use a 45 gallon drum or air compressor tank etc as an accumulator.

Regarding ol89er's mention of 2wd, it seemed to slip by whoever read the thread that the Yamaha system generated no front wheel drive torque until the rear spun substantially, as a difference of wheel rpm's was required to generate drive pressure to the front wheel hydraulic motor, at which point the front wheel would start to do some pulling. So on solid terrain you would have rear wheel drive, on sand and goop you have 2wd. I realise the hydraulics to the front are extra weight and inefficient, but throw a big enough motor at it and hp stops being an issue vs having a rideable bike in offroad conditions (I cite the mellowing-tuning of CR/KX500's for controllability) (excepting situations like flat out desert running and super motard where traction isn't such a limiting factor to overall performance). A bit heavier bike is all a matter of perspective after seeing the Dakar bikes in action. The scheme seemed like an offroad limited slip traction control in final effect. I'd like to try out such a beast some day.


Posted by: gblair

..to all..

as in 'Porting and Flow' no action here since 5 February..so I'm off on holiday, I think! The tuning business must be at a low ebb I think!


Posted by: Brianc

Hello Professor,

I was wondering if the ratio of bore to stroke of a given engine size would affect the prefered port diameter and length of the induction system. The example being 187 cc single cylinder engine. One combination is 63.5 mm bore x 59 mm stroke as compared to a bore of 69 mm x 49.5 mm stroke. I am curiuos as whether the increased depth of the cylinder would necessitate a higher gas velocity to properly fill an engine with a longer stroke and smaller bore vs the engine designed with the shorter stroke and bigger bore. Would the volumetric efficeincy of one design be higher than the other design ? Of course all other variables ( porting, carb, cam, etc) are the same .


Posted by: Swiss

Small Honda engines with 2-v heads?

Swiss


Posted by: LEE BAXTER

To Profressor Blair I have an idea in my head about 4st engines.It is a reed inducted four stroke engine which at first thought seemed very simple until I thought I needed a sub-chamber to take care of the gases on the 2nd stroke . Has this been tried or am I barking mad ?


Posted by: gblair

..to Mr Baxter..

..automatic (ie light spring-controlled only) intake poppet valves were very common around the turn of the 20th century. I don't think I know of anyone trying a reed valve to replace the poppet valve as it would suffer terribly during the combustion process. There was a fad at one time of trying them as a kind of automatic turbulence creator in the intake tract behind the poppet valve but they reduced air intake flow and hence power output very considerably.


Posted by: gblair

.to Brianc..

..assuming you are talking about high-speed dirt-bike engines and not a 3600 rpm generating set then oversquare engines more easily permit larger valves and ports than undersquare engines and that all leads to higher airflow and exhaust gasflow rates and, hence, power outputs at higher engine speeds.
There is only a very minor correction for intake tract length for tuning at a particular speed as a function of change of the intake tract diameter. Essentially, intake tract length is more pronouncedly a function of engine speed alone and of the intake valve lift duration. You should read the appropriate section (Chapter 6) of my textbook for a fuller explanation of your entire "question in two parts".


Posted by: Brianc

Thanks for your reply.

That is what I had thought, I was wanting verification because it has been 20 years since I studied high performance engine tuning.

To what textbook are you referring?


Posted by: Rich Rohrich

Quote:
Originally posted by Brianc
To what textbook are you referring?


SAE# R-186 : Design and Simulation of Four-Stroke Engines
This book provides design assistance with the actual mechanical design of an engine in which the gas dynamics, fluid mechanics, thermodynamics, and combustion have been optimized so as to provide the required performance characteristics such as power, torque, fuel consumption, or noise emission. Many engines (including a number of famous ones) are used as design examples and analyzed.

http://www.sae.org/servlets/product...K&PROD_CD=R-186


Posted by: gblair

..to Mr Rohrich...

...you certainly beat me to the punchline there...


Posted by: gblair

to Brianc....

..if ALL other variables were the same (Compression ratio, valve sizes, timing and lift, etc) then the bore-stroke ratio would barely affect the air-flow issue..only the slightly differing surface areas giving slightly different heat transfer effects would change the airflow slightly...although the combustion behaviour in the engine with the lower bore-stroke ratio could well prove to be superior.

..the whole point about a larger bore-stroke ratio is to permit larger valves and lifts so that the engine will produce the 'same' torque but at a higher engine speed and so more power output. If one were designing a generator engine at 3600 rpm the argument in favour of a square, or even under-square, bore-stroke ratio becomes quite compelling in performance and emissions terms.


Posted by: cujet

gblair, I would like to hear your ideas on the these 2 questions. I have formulated my own "facts" on these subjects over the years. However your input is wanted. It would certainly help me to clearly explain these thoughts to others.

1) Small intake ports, websites such as this. http://mototuneusa.com/super_sonic_nozzle.htm
He seems to push making every intake port smaller. He also seems to make statements that smaller ports make more HP.

2) bore and stroke vs. torque. With all else equal. Many people claim that longer stroke engines proudce more torque.

I would love to have your input, and hope you would share some experiences and/or theories to help explain your answers.

Thank you

Chris


Posted by: gblair

to cujet....

...question no.1..I hate to do this to you but the answer is not universal and so much space to this topic is given in that textbook that I have written (SAE ref. R-186) where it is impossible to repeat here what took me many pages to write in that book.

..question no.2...again the answer is not universal and it all depends on what piston speed the engine is designed to produce its peak power. At very high mean piston speeds (say 22-26 m/s) the oversquare design will be the winner and at very low piston speeds (say 10-15 m/s) the undersquare engine can be the winner assuming that it is designed correctly.


Posted by: Swiss

OK Dr. Blair, I just got your book delivered. Of course, now I will have to read it through a few times and then jump back into some math background with extensive study to figure some of the things out. It is of course much more detailed than say a typical Car or Cycle magazine article that just simply explains a rough approximation of how things work and then gives you a generic formula to use for better performance. I look forward sometime to getting your program, but figure that I should understand the background that is explained in the book before I let the computer do most of the Work for me!
A friend loaned me his copy of "Design Techniques for Engine Manifolds by Winterbone and Pearson". While extremely detailed, it constantly refers you to other texts and research articles without giving you the information meeded to understand what is being said. In a quick review of your book, I haven't found this to be a problem at all. Thanks for your detailed analysis and information. Will your book answer ALL of my questions? Probably not, but I doubt that you ever ran out of questions either.

Swiss


Posted by: Swiss

Originally posted by cujet

1) Small intake ports, websites such as this. http://mototuneusa.com/super_sonic_nozzle.htm
He seems to push making every intake port smaller. He also seems to make statements that smaller ports make more HP.

2) bore and stroke vs. torque. With all else equal. Many people claim that longer stroke engines proudce more torque.

Chris/cujet,
I first went to the mototuneusa web site sometime last year and read through his radical new ideas. First of all, I have seen this same type of information printed a number of times over the last 30 years in various car and cycle publications. He hasn't got any new ideas that others haven't worked with for MANY years. Typically, it seems that port sizes and flow speed numbers vary through the years. As various Cycle engines (our normal topic) are developed by the factories AND their race teams, the porting goes through several often repeated steps of development. These same basic 600cc engines that are mentioned specifically on his site are used for daily grocery getters as well as Factory Race Bikes. Some race classes require minimal head/port work on the engines.
Anyway, yes in some cases you can reduce the port size and or change the shape to enhance engine performance in some segment of the powerband. IF this is the ONLY change that you make, then the engine is NOT being optimized, only refined. Will those larger stock ports work with the factory racing cam and carbs and pipe combination? Probably. It is getting harder and harder to beat the factories for performance without some fairly large changes. Small benefits? Yea, these engines aren't perfect from the factory, but smaller ports and "higher" velocities aren't the final answer to the performance questions.

On the "stroker" question, it is a nice relatively small displacement increase for a performance gain. As Dr. Blair mentioned, it is not that simple. It often depends on where you are measuring the gain in performance and very much depends on whether the longer stroke works with the other engine tuning. I have noticed that MOST 4-stroke MX riders aren't using their top end hp except on the start line run. For the rest of the track, they are constantly in the bottom or mid-range of the powerband. A mod that enhanced low and mid-range at a sacrifice of a little or possibly no real gain at the top would work fine for them. It used to be that Open class 4-strokes lacked some peak hp, but with most of them now putting out between 45-50 hp it is a good controllable mid-range that is important. One of the tuners that I have talked with recently said that they are testing smaller exhaust pipe systems on the big Thumpers. He DIDN"T say that they were looking for more peak hp. As Dr. Blair said, it is a pretty complicated issue. Honda played with this issue back in the mid-'70s with their TL250 trials bike. The XL250 engine was considered to be RADICALLY oversquare at that time, but Honda made a Trials bike out of it with a smaller carb, porting, milder cams and a quiet restricted pipe. With bore/stroke ratios in the 1.5-1 ratio and beyond for some Street bike engines, this engine isn't considered Radical anymore. But compared to the other engines on the market at the time, it was! Honda was told that they COULDN'T build a short stroke engine that would produce good torque. Fortunately that didn't stop them from doing it.

Swiss


Posted by: gblair

to Swiss..

..glad you got the book....and of course no book can ever answer ALL of the questions....and as you say I have thought of, and put to myself, many questions since and some even got answered!


Posted by: gblair

to cujet...

..you had better read THAT book again...most of what you want to know is in there...

..and there are no universal rules that smaller (than what) or larger (than what) ports to make more hp....for any engine in the role that is envisaged for it (ie MotoGP, motocross, etc.) there are optimum sized ports, compression ratio, valve sizes, valve lifts and valve lift profiles to optimise the peak hp and the hp spread over a speed range to give the rider the best chance of winning the relevant competition. So don't search for rules, search for understanding of how an engine breathes and produces power to satisfy the 'requirement'....in short it is back to reading THAT book again!


Posted by: Rich Rohrich

Quote:
Originally posted by gblair
don't search for rules, search for understanding of how an engine breathes and produces power to satisfy the 'requirement'


Now there's a quote worth repeating. :thumb:


Posted by: cujet

Gblair, good to hear from you again on this subject. I often make the mistake of not asking very specific questions, and expecting the answer to what I was thinking. A major flaw of mine! The answers I am looking for are not of the "What is best" type. What I was looking for is how you might respond conversationally to the often heard statements: 1) longer stroke makes more torque. 2) smaller ports win races.

I do not like such statements. I have personal experience with short stroke high torque engines. However I have never been able to give a succinct accurate response to such a statement. I suppose I would like to be able to respond with just the right facts to allow the recipient to open his mind a little, without going into too much detail.

When discussing a particular engine I might bore someone to death talking about overlap, lift, duration, valve area, port length, compression ratio and the like.



Chris


Posted by: gblair

to Rick Rohrich...

....I think you mean it is not too bad considering it is from one of those old 'go-fast guys' don't you?!


Posted by: gblair

to Cujet...

...beware of all supposed truisms...and universal rules on engine design that are about as generally applicable as a hot linseed poultice is for curing all carbuncles....and, please, Mr Rohrich, do not quote me on that!


Posted by: Rich Rohrich

Quote:
Originally posted by gblair
to Rick Rohrich...

....I think you mean it is not too bad considering it is from one of those old 'go-fast guys' don't you?!


Something like that Professor.


Posted by: Swiss

Prof. Blair, if you are still monitoring this list? I am working on getting through your book and enjoying it a lot, however, I was wondering about changing parameters in pulse tuning and how they effect the typical formulas. For instance, I have a friend that is racing a 650cc four stroke and running it up to 10k rpms. From a previous dyno chart, he is making strong power up to the rev limiter so we are tuning it for about 8.5k to 9k rpms for max power. Problem is with carburation, as the formulas that I have show that for that displacement and rpm, the ideal carb (single unit) would be in the 60mm range, or a pair of 40-41mm units. Since this is a 4-v head but with a single carb mount, he can only realistically fit a 46-48mm carb on it. You know small limitations like casting port wall thickness and such will probably also keep him from even trying to go to a +50mm or bigger carb anyway. So, what variations can be made to allow for the increased velocity of running a smaller carb with this engine displacement and increased intake velocity. If he runs a 46mm carb, the formulas that I have show a tuned rpm of about 5k with a tuned length of about 19.5" (3rd harmonic, which is of course too long to use). Given the real increase in velocity that using one of the smaller carbs will cause, what variable can I figure out for setting a reasonable length for the increased velocity? I know that your program will probably figure this all out for me, but I probably won't be able to afford the program until sometime next year. Got too many project cars and bikes to fund money into this year.
Thanks for any help.

Swiss


Posted by: Swiss

Rich,
I am working through the book but I would like to see some Pressure diagrams for intake and exhaust systems over a wider rpm range. I now understand that the curves "stretch" as the rpms rise, but I would like to see what kind of Pressure diagrams would be generated from say 3k to 10k rpms with a given engine like a 426/450 Yamaha. It is the progression of the "stretch" in the curves that has me interested. Most of the book charts are for specific rpms or only a couple of close rpm ranges, and not over a full powerband for an engine. If you can work with me on this, I would appreciate it, as I won't be able to afford the programming until I finish a couple of projects. I guess the main info on this is in the area of the book for the ITC single design. Also trying to figure out the general effects of tapered angles in both the intake and exhaust. Have figured out that the taper lessens the amount of the effect, and also shortens the required tuned length, but don't have a firm idea of how much for a given specific angle. In Design Techniques for Engine Manifolds by Wintervone and Pearson, a 13% difference in intake length is mentioned for a tapered Inlet length. I would like to start tying the idea of pressure diagrams and tuning together.

Thanks for any help you can offer.
Swiss


Posted by: gblair

to Swiss...

as you can see I do not monitor this page too often as you are the first questioner for months!

I am afraid that the answer to your many interesting questions can only be answered by using engine simulation software as once one departs from the areas where empiricism has been established it is not fruitful to start second-guessing the motions of pressure waves of differing amplitudes. That is what a simulation is for with empirical rules of thumb reserved for the initial guesses at the input data. Tying pressure diagrams and tuning is what it is all about bout those diagrams can only come from an (ACCURATE) engine simulation calculation when some of the off-design and off-speed input data is computed for their effect on the P-t diagrams and the power, torque and airflow.


Posted by: Swiss

Dr. Blair,
So, does the programming allow for
1. variables such as different length air bells on the intake, and for
2. variations of the meg. length and diameter.
3. will the program allow me to examine the effects on the entire rpm range of various changes? Is this set as separate pressure diagrams for each rpm and then I could string them together, or is there a way to view the differences in an elongated format that would allow me to move horizontally along the rpm time line? Don't know if I am stating this question correctly, as I don't have the program yet to find out what its capabilities are.
4.Also, on another forum, some of the guys were trying to simplify the reverse cone of the megaphone design as simply an Anti-Reversion effect. This doesn't sound right to me, but I haven't actualy seen a good definition of the differences between say a meg without and one with a reverse cone. Or if I have, I can't recall the exact results.
Thanks for your time,
Swiss


Posted by: Swiss

Quote:
Originally posted by gblair
to Swiss...

...as once one departs from the areas where empiricism has been established it is not fruitful to start second-guessing the motions of pressure waves of differing amplitudes. .... Tying pressure diagrams and tuning is what it is all about bout those diagrams can only come from an (ACCURATE) engine simulation calculation when some of the off-design and off-speed input data is computed for their effect on the P-t diagrams and the power, torque and airflow.


Gaining knowledge is painful, but it is getting better! I am seeing what you are saying on the information available from the programming.

Swiss


Posted by: Rich Rohrich

Quote:
Originally posted by Swiss
If you can work with me on this, I would appreciate it, as I won't be able to afford the programming until I finish a couple of projects. I guess the main info on this is in the area of the book for the ITC single design.


Hi Swiss - Sorry, I must have missed this when you first posted it.

I don't currently have my own copy of Virtual Four-Stroke, but I can occasionally get limited access to it through a friend at a university. If you want to outline the specific parameters you wanted to test I can try an coordinate running the test through him. I'm always interested in advancing my knowledge as well :thumb:

In the meantime you might want to have a look at Professor Blair's SAE paper "Exhaust Tuning on Four-Stroke Engine;Experimentation and Simulation" (SAE # 2001-01-1797)

Here's the abstract from the paper :
ABSTRACT
A Yamaha YZ400, 5-valve, 4-stroke cycle, motocross racing, motorcycle engine is instrumented to provide pressure diagrams in the exhaust system which are recorded over the usable engine speed range at full throttle from 5000 rpm to 11000 rpm. The engine produces a maximum of some 34 kW (46 hp) power output. The production muffler-ended exhaust system is replaced with two alternative and more highly-tuned exhaust systems, namely a straight pipe and a straight pipe and diffuser. The complete engine geometry together with these two exhaust systems is simulated using an
engine simulation software package (VIRTUAL 4-STROKE) and the experimentally-recorded exhaust pressure diagrams and performance characteristics of power, torque, etc., are compared with the predictions of the theoretical simulation.
The variation of exhaust system produces differing performance characteristics whose origins the measured pressure
diagrams and recorded performance characteristics struggle to explain. The simulation, on the other hand, not only computes accurately the exhaust pressure diagrams and the performance characteristics over the entire speed range but also explains the origins of the variations in these performance characteristics. This illustrates not only the effectiveness, or otherwise, of this type of exhaust tuning on four-stroke engines but also the effectiveness of an accurate engine simulation as a design and development tool. Finally, from the experimental and simulation evidence presented the paper draws numerical conclusions on empirical design factors for the basics of exhaust system tuning.


Posted by: Swiss

Thanks Rich, I seem to remember this being mentioned several months ago. I will see if I can either obtain a copy of the SAE paper through the local library, or pony up to SAE and order one. It SHOULD alsnwe a fair number of the current questions that I have. Then I will get back with you and see if we can set up some educational testing plans that will give us some of that needed "learnin'".

Swiss


Posted by: Swiss

Rich and Dr. Blair and anyone else that may have an idea. There are always comments made about polishing ports affecting the fuel suspension and mixing etc.. First of all, there is no mixing in the exhaust port, so polishing the exhaust should be fine.
Some thoughts.
Now, for the intake port, at what point does fuel in the intake port begin to separate and pool? Is it a specific or approximate flow velocity? I am sure that it will vary for each engine/port design to some extent. IF the port is a downdraft, will that get rid of the pooling problem? I don't see anything wrong with polishing the TOP and sides of the port and leaving the bottom of the port a satin or slightly rougher finish to prevent separation. Any validity in this idea? Has anyone ACTUALLY tested it? Paul Olmstead of Powroll told me many years ago that a polished port would flow about 1% additional CFM over a non-polished port of the same size. In a typical mid-sized cycle head that can be a couple of CFM (at the 15" that Powroll had their flow bench set for). This amount doesn't seem like much, but race porting of a factory head often ONLY nets a 5-15% gain in intake flow. So, another 1% is anywhere from a 6 to a 20% additional amount of the overall gain.

Comments?

Swiss


Posted by: gblair

to swiss..

..polishing ports is always a good idea as the mirror finish shows up shape imperfections so clearly and then those can be again removed....and has no effect on fuel pooling or mixing...but exhaust ports soon coat over with carbon and the mirror finsih rapidly disappears.


Posted by: gblair

to swiss..

..in the book there are loads of pressure diagrams at different speeds on many engines so that the effects you ask for are (I hope) clearly illustrated.

..as to your friend's engine that solution is a task for VIRTUAL ENGINES software and cannot be answered simply as too many design geometry variables are involved.


Posted by: gblair

to all readers..

I have just written some articles in a magazine called Race Engine Technology and the movies of the pressure diagrams and the CFD calculations within the airbox restrictor pipe are uploaded on to the www.profblairandassociates.com website as a free download to all who want them. You will find them informative on engine tuning..but you really need the Race Engine Technology articles to full understand want you are looking at.


Posted by: Rich Rohrich

Thanks for the update Prof. Blair.

Could you lend some guidance on getting the correct valve area dimensions in the SAE version of Virtual Four-Stroke? I'm attempting to model 5 valve Yamaha engines within the four-valve limitations in this version. I was hoping you might be able to share some advice on keeping the fudge factor to a minimum and the results as accurate as possible.

Thanks.


Posted by: gblair

Quote:
Originally Posted by Rich Rohrich
Thanks for the update Prof. Blair.

Could you lend some guidance on getting the correct valve area dimensions in the SAE version of Virtual Four-Stroke? I'm attempting to model 5 valve Yamaha engines within the four-valve limitations in this version. I was hoping you might be able to share some advice on keeping the fudge factor to a minimum and the results as accurate as possible.

Thanks.


Sorry to be so slow in replying...I have been off elsewhere working recently...as to advice I am not sure exactly what you want and I suppose all I can say is that it is not satisfactory to attempt to model in Virtual Engines a 5-valve engine when the SAE limited-edition model only handles 4 valves. Sorry!...otherwise it's a GIGO job..garbage in is garbage out!


Posted by: Rich Rohrich

Quote:
Originally Posted by gblair
I suppose all I can say is that it is not satisfactory to attempt to model in Virtual Engines a 5-valve engine when the SAE limited-edition model only handles 4 valves. Sorry!...otherwise it's a GIGO job..garbage in is garbage out!


Thanks Professor Blair. I had assumed that trying to trick the limited version of the software into modeling a 5 valve engine was an excercise in futility, but I figured it couldn't hurt to ask.

One more reason to spend my limited development funds on the 4 valve CRF Honda engines I guess.

BTW, I read the RET articles you wrote. It will probably take about 30 re-reads to fully grasp it all but it sure was nice to get that level of detail. Thanks for sharing it with us. You can tell the editors they have at least one new subscriber as a result of your name on the masthead. :thumb:


Posted by: Jason B

Rich, Eric, or Prof. Blair;

I've been lurking in the shadows, reading this thread for about 6 months. I have been also reading alot about 4 stroke engines, as I am a recent convert. I am now going to say the dreaded "C" word, Cannodale! Yes I said cannondale.

Having ridden 250's for a long time, and being a customer of Eric Gorr's, as well as sending several customers his way, I feel that I am qualified enough to know a good motor when I ride one. Even though a 2 and 4 stroke have different characteristics you can tell when your on a turd. Despite what all the "mags" say, the X440 is not a turd. There are plenty of riders of all abilities that do very well on these bikes.

I have a feeling that the Professor has an inside scoop on the development of that motor. Rich, give your opinions as well, as I might have you guys do some head work on it in the future. That is if your up for it. Eric, I will always give, and send as much business your way as I can. You are the "Cats Meow."


Posted by: Rich Rohrich

Jason - You should probably start a new thread in the Thumper forum where you are bound to get more response.


Posted by: klxrdr

Dr. Blair, Rich, Swiss asked a question that I didn't see answered. What are the features-capabilities of the SAE version of Virtual 4-Stroke?

Tried calling Optimum. They were great folks to talk to and could talk my ear off about the commercial version, but they really didn't know much about the SAE flavor.

Is there a demo version of Virtual 4-Stroke (SAE) available?

One of the reasons I ask is that I recently took a test ride on a demo version of Dynomation Four Stroke. There was no program documentation available but the inputs seemed intuitively obvious.

After working with the program for a while I discovered the exhaust entries did not allow for modeling megaphones with a reverse cone, or silencers. I thought this odd given the nature of the program and was wondering if Virtual 4-Stroke SAE had similar limitations?


Posted by: Rich Rohrich

Quote:
Originally Posted by klxrdr
Dr. Blair, Rich, Swiss asked a question that I didn't see answered. What are the features-capabilities of the SAE version of Virtual 4-Stroke?


From the SAE description of the software:

This engine simulation model on CD-ROM, available for installation on IBM PC (or compatible) computers, is based on the theory within the various chapters of the book, Design and Simulation of Four-Stroke Engines by Gordon P. Blair (Order No. R-186). The application of the model is discussed in Chapters 5-7. The engine simulation model will simulate a single-cylinder naturally-aspirated four-stroke engine with the following attributes: almost any two-valve or four-valve cylinder head; almost any intake ducting geometry and simple silencer; and almost any exhaust ducting geometry and simple silencer.

In addition, the model allows the following: Selection from a menu of Diesel and Otto cycle combustion processes; Varying of Otto and Diesel fuelling over a sufficiently wide range; Selection from a limited menu of discharge coefficient maps for valves, etc.; and Selection from a limited menu of diesel and gasoline fuels.

The user can insert input and output data into other graphics packages and retrieve the input data for further design activity. The output data appears as a prediction of the engine performance characteristics, including power, torque, fuel consumption, airflow, emissions and noise characteristics. Users must have Microsoft(R) Excel available on the computer to observe the graphic output data from the simulation.


Quote:
Originally Posted by klxrdr
After working with the program for a while I discovered the exhaust entries did not allow for modeling megaphones with a reverse cone, or silencers. I thought this odd given the nature of the program and was wondering if Virtual 4-Stroke SAE had similar limitations?


The SAE version can model megaphones or any other complex exhaust design.


Posted by: klxrdr

So Rich, can Virtual 4-Stroke (SAE) model a reverse cone of various tapers on a megaphone?

As far as documentation, does the Professors book double as the program user guide?

Is there a demo version of the SAE program available?


Posted by: Rich Rohrich

Quote:
Originally Posted by klxrdr
So Rich, can Virtual 4-Stroke (SAE) model a reverse cone of various tapers on a megaphone?


Yes


Quote:
As far as documentation, does the Professors book double as the program user guide?


There is excellent tutorial and help info with the program, but Professor Blair's book is mandatory to understand the underlying theory and to really take advantage of the program's capabilities.

Quote:
Is there a demo version of the SAE program available?


I didn't see one listed on the SAE website.


Posted by: gwhII

I've gotten here way late and re