A differant jetting idea

bh

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#1
Has anyone out there ever had their bike jetted by a tuner with a dyno and one of those exaust gas anaylizer things? My uncle is buddies with a national flat track mechanic who can do this for me. Anyone had any experance with this? Thanks in advance.
 
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#3
It would be quite an extensive process what with multiple carb circuits/throttle postions.

If it's done right it should work pretty well. There have been references to tuning with 'sniffers' before. It's generally considered a rather esoteric hi-falutin' way of doing it.

...not something you'll have access to on your next trail ride!

If you learn something in the process it would hold you in good stead when the temps drop 30ยบ and/or barometric pressures change a few inches of Hg.

A bit easier to get that learnin' if your 'hinder is your response gauge. ;)
 

bh

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#4
I realize that the experance would be valuable but I just siezed mine and I think it was runnin to lean. Now im kinda scared of doin that again. And I would only use it as a base setting.
 

palmer69

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#5
If you do it, you'll be my hero! Some real science. I think it's a great idea. I wish I had access to the machinery to do it. I'd love to see some real world dyno comparisons with all the popular mods: airbox lid on/off, snorkel on/off, holes drilled, torque ring, jetting etc. etc.

Do it, do it, do it, do it....
 

Rich Rohrich

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#6
The exhaust gas analyzers that sniff the tailpipe react too slowly to be of any use for transitional throttle settings. With a little work you could get a baseline for WOT that could be of some value when making future mods. Some people use these to set the CO level for idle on four-stroke singles but I've never seen anyone that had much success on a two-stroke single and this type of equipment. Probably due in large part to how erractic the scavenging is at idle on two-strokes.

A wideband O2 sensor connected to a fast data acquisition system is the only affordable way I know of to do it for the average racer. Even that isn't cheap, but it can be used provide real world data from the track or the trail. The karting guys have used wideband technology for years with great success.
 

Jim Crenca

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#7
Rich had documented both the limitations and practical issues invloved with trying to use an exhaust gas temp device as well as an O2 sensor in a 2-stroke application. My experience with karts & drag cars was that an exhaust gas temp probe and data storage worked OK for WOT measurements but probably no better than cutting a plug open.

For you tuners out there; if the thread in Advanced Tech is still around, you will find an incredible SAE paper presented by Honda that talked about a "detonation counter" found by Mr R.; sounded like many data aquisition sensors and proprietary micro processors.

Rich, is the little $200 box I see on the hi tech kids modified imports documenting any real data?
 

Rich Rohrich

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#8
Originally posted by Jim Crenca
Rich, is the little $200 box I see on the hi tech kids modified imports documenting any real data?
Jim - It really sort of depends on the O2 sensor that is attached to it . Unheated two state sensors are common in these inexpensive units. They basically generate a voltage based on the differences in oxygen between a reference slot the to outside air and the oxygen the sensor element sees in the exhaust stream. The problems start with temperature. The sensor's curve is sensitive to temperature and it's really only accurate over a fairly narrow air/fuel ratio range near 14.7:1 (i.e chemically correct combustion). Sensor response time varies greatly with temp as well. The better dashboard units will have a heater element built into the sensor powered by 12 volts that will stabilize the sensor temps to keep them responding quickly, but they are still subject to the narrow accuracy range of the basic sensor design.

The next step is to go to a ~$300 wideband heated O2 sensor and feed that data into a fairly fast ( up to 1000hz) data acqusition system like the Drack Evo 3 ( http://www.aim-sportline.com/moto/logger.htm )

The wideband sensors due to much more advanced circuitry can accurately measure air/fuel ratios from 10.5:1 all the way about to about 50:1 and they can respond to changes in a/f ratio quicker.

So I guess the basic answer to your question is maybe they are getting useful info. :)

They are fun to play with either way. What's really fun is connecting a laptop computer to the OBDII clip under your dash and reading all the sensors in real-time while you drive. It's really enlightening to watch what happens to the O2 sensors (before and after the converter) and the ignition timing as the MAP sensor and TPS readings change and the various temperatures are manipulated. It's a great way to kill a rainy day when you can't go riding. :)
 

bh

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#9
Thanks for the feedback I think I will go ahead and try it if it doesn't cost too much.
 

Jim Crenca

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#10
It would cost lots to do it right.
I would suggest that you pay a good local mechanic to jet the bike properly the old fashined way (which can not be done properly in the dealers parking lot).
 

bh

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#11
Yeah I've had some time on my hands today and I have been reading lots on jetting and I think I can do it myself without too much trouble. I don't think I'll sieze it again I reckon maybe that was a test that told me it was too lean! So when I put my bike back together I'll go a couple sizes richer on the main. Thanks again. I have no idea what I whould do without DRN
 
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#12
Originally posted by bh
I realize that the experance would be valuable but I just siezed mine and I think it was runnin to lean. Now im kinda scared of doin that again. And I would only use it as a base setting.
bh which model KDX and what year? are you running 32:1? where in ohio do you ride, SE in Wayne NF by any chance?

I've got an 03 KDX 200 running Sunoco 94 and Castrol TTS @ 32:1. Have removed the snorkel and rejetted to 45 pilot and 155 main as per the tech section with great success in better power and throttle responce.....but my last ride I began to notice sort of a pinging noise when I have to chop the throttle from high RPM. It could be chain slap as I had about 2.5" slack, or maybe the KIPS valve shutting or the throttle jet needle slide getting sucked back closed by vaccum. I do not have any area to do a plug chop at all and I am afraid I am hearing detonation and am on the lean side.

I am not that concerned with running on the ragged edge of tuning. I would prefer to have a jetting setup that keeps me safe @ 1000 feet from 20F to 90F for SE Ohio year round. Or maybe at the worst a summer and winter setup.

My buddy also has a dynojet in his garage. He and his crew all have VMax's on the bottle putting 150-170RWHP. We've done my SV and other sport bikes, I could easily see doing a 1/4, 1/2, 3/4 and WOT plug chop along with the exhaust sniffer he has on the dyno except I don't know what happens w/ knobby tires on the dyno drum.
 
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#13
re: 'If it's done right it should work pretty well'

That's my way of saying it isn't going to be done right...probably can't be done right...and if it COULD be done right...it still most likely aint' going to be done right.

But I didn't want to rain on his parade.......;)

btw...what happens with a knobby tire on a dyno drum is nothing. ...cuz you change it to something with no knobs. Well...not an absolute necessity I 'spose, but that's been my observation of dyno runs with off-road machines.

A further btw..you can seize a 2-smoke even without a too-lean jetting setup. Worked for me!

Where it seized (I don't mean 'tearing up knucklesnapper in 3rd gear @ WOT) will tell a good tuner/mech what happened.
 

bh

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#14
Hey mad_german I live in Adams county and ride mostly on about 600 acres that my parents and grandparents own. When I siezed mine (93kdx 200) I was running a 150 main and a 48 pilot with 32:1 93 octane pump gas. For some stupid reason I never even opened up my carb till it siezed! Seemed to run good and that was the first time I really held it open for a long amount of time. At least I learned a lesson.
 

bh

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#15
Oh yeah I have a PC pipe, air box lid removed, Boyesen power reeds, and using Klotz Super-techni plate oil.