Jetting with EGT or O2?

[EnduroDude]

I am playing with the idea of monitoring Exhaust
Gas Temperatures or O2 content for jetting changes.

Is anyone having good or bad luck using EGT or O2 for
jetting? With research I have learned that 1100 degrees EGT
is optimum but won't those temps be lower during 1/4 or 1/2
throttle settings as apposed to 3/4 and wide open?
And what about sensor placement?

O2 on 2 strokes is optimum @ 12:5 to 1, But I am thinking
an EGT sensor will out last an O2 sensor in that
environment.

 

[EricGorr]

Theres a raging debate about that. Some tuners believe in placing oxygen sensors in the convergence cone of the pipe, others claim it won't work because there is so much raw fuel traveling through a pipe because of short circuiting.
Karters use temperature sensors to monitor exhaust gas temperature to shut the engine down before a seizure occurs. I use an OPTAK, a now defunct company that made a combo EGT/RPM gauge designed for the harsh off-road motorcycle environment. Its very difficult to get a dirt bike up to temperature, and the 1100F target can only be achieved at wide open throttle. When riding enduros through the woods the average EGT is 400-600F measured 6 inches from the exhaust face of the piston.
I advocate the Ride and Feel jetting method, because throttle response is subjective to rider skill.

 

[EnduroDude]

Originally posted by EricGorr
Theres a raging debate about that.

Hi Eric,
I asked this same question on www.iATN.net as I do allot of technical brainstorming there that is job related.

There Larry McCoy wrote:

You may have run across it already, but this guy's site is
one of the best I've found http://www.eric-gorr.com/

I talked with him on the phone once, he couldn't be a nicer guy, and he really knows his stuff.

Guess Larry is right, how nice to take time in your busy schedule.
For a couple years I handled consumer automotive questions on-line and it was tough!

Some tuners believe in placing oxygen sensors in the convergence cone of the pipe, others claim it won't work because there is so much raw fuel traveling through a pipe because of short circuiting.

What section is considered the "convergence"?
I work with late model automotive EFI systems and I don't understand what you mean by "short circuiting"
If there is too much raw fuel in the exhaust that would tell me the combustion is being fed more than it can handle and thus be too rich on fuel and the O2 will read that.

Karters use temperature sensors to monitor exhaust gas temperature to shut the engine down before a seizure occurs. I use an OPTAK, a now defunct company that made a combo EGT/RPM gauge designed for the harsh off-road motorcycle environment.

Hrmmm...so you do use one for evaluation

Its very difficult to get a dirt bike up to temperature, and the 1100F target can only be achieved at wide open throttle. When riding enduros through the woods the average EGT is 400-600F measured 6 inches from the exhaust face of the piston.

I have not installed one just yet but 6" seems to be way to far and would be the reason temps drop off at slower speeds. For Enduro type of ridding I would think the closer the better. The farther down you go EGT's have the opportunity to cool.
Many race car engines have them in the port rather than the header.

I advocate the Ride and Feel jetting method, because throttle response is subjective to rider skill.

That is what I have always done but seems to me there is room for improvement with todays technology.
Your input is extremely appreciated Eric and once again thanks for taking time.

Matt

 

[EricGorr]

Matt, the convergence cone is the last cone in the pipe. Roadrace tuners in the Netherlands started the trend of fitting a Lambda sensor in that cone to get an accurate reading on the oxygen content without the threat of reading a rich mixture from short circuiting gasses. Short circuiting occurs mostly at lower rpm. Unburnt mixture gasses exit the transfers and short circuit out the exhaust because the plugging wave (compression wave) isn't strong enough or at the proper frequency to push the unburnt gasses back into the cylinder before the piston closes the exhaust port. Thats why the EPA is critical of 2-stroke engines, short circuited hydrocarbon emmisions.

I wish that Sean Hilbert of REV! Motorcycles was here to read and respond to this post because he gave me a better explanation a few years ago, but I've forgotten some of the details since then. Perhaps DOC or Phildirt are reading this and can add their opinions. They are much more qualified than I am to answer the EGT vs. O2 debate. Those guys have performed extensive dynamometer testing on 2 stroke engines, measuring the temperature, and purity of the exhaust gasses in accordance with rpm, load, throttle position, etc.

Regarding the 6 inch spacing of the temperature probe, its sort of an unwritten standard and I think that it has more to do with the flame travel down the pipe, giving a false reading.

As far as the OPTAK is concerned, I still use it occasionally. Its more usefull to observe what rpm range and temperature that a particular rider attains on certain sections of the track. The use of jetting computers was banned by the FIM and AMA by 1994, and I suppose thats my fault because we used it in a few 500cc GPs during practise and some of the Italian teams blew a gasket crying foul. The sad truth is not many factory mechanics can actually ride a bike or jet it.

 

[Rich Rohrich]

Here's a thread that had some interesting info on the subject:

http://dirtrider.net/forums3/showthread.php?s=&threadid=37556

 

[EnduroDude]

Originally posted by Rich Rohrich
Here's a thread that had some interesting info on the subject:

http://dirtrider.net/forums3/showthread.php?s=&threadid=37556

Thanks for the link but when I click on it I get this error message:
DRN Forum Message
Sorry!
You'll need to become a member of the forums (it's free) before accessing these topics. You can register [ by clicking here ].

Already a member but not logged in? Enter your log-in below: Login with username and password:


I am logged in so don't know what to do about that???

 

[EricGorr]

The link worked fine for me. Theres a good post by Sean Hilbert that explains the O2 question.
Thanks for the link Rich, as usual you know where all the goodies are hiding!

 

[EnduroDude]

Originally posted by EricGorr
The link worked fine for me. Theres a good post by Sean Hilbert that explains the O2 question.
Thanks for the link Rich, as usual you know where all the goodies are hiding!

Still does not work for me, possibly because I am only a "registered member" at the moment? I also notice as a registered member I can't search old posts so maybe I can't "view" them either??

 

[EnduroDude]

Eric,
What are your thoughts on this tool:
http://www.aimracingproducts.com/page4.html

 

[Rich Rohrich]

You can find the above thread in the Advanced Technology Forum the Subject is "Injected two strokes"

As for the O2 sensor setup you listed. Unless you use a heated wideband O2 sensors like the Bosch LSM 11 or NTK L1H1 all you can "accurately read" is the exact Lambda point and only when the exhaust has heated the sensor element to the correct temperature. Cheapy narrow band O2 sensors have a HUGE temperature dependent slope in their outputs once the O2 content starts moving away from Lambda. So as a device for trying to setup an engine for best power mixture, the simple O2 sensors are a poor choice. It's hard to tell from the link you sent but based on the pricing this appears to be a narrow band setup. Make sure you check with the company and get the specs on the sensor before you spend you money. An alternative that you might want to consider is http://www.jandssafeguard.com/monitors.html . This device is designed to work with the Bosch LSM 11 sensor . More info on this is available from Dr. Dave Redszus at Precision Automotive Research, at (630) 766-4402 .

Eric and I are using the Bosch sensors connected to an 8 channel data acquisition system to take these readings along with MAP, EGT, TPS, intake air temp, and a few other things. We are just using this setup on four-strokes currently though.

Good luck, it's worth the money and the effort to tune this way. :thumb:

 

[EnduroDude]

Originally posted by Rich Rohrich
You can find the above thread in the Advanced Technology Forum the Subject is "Injected two strokes"

Thanks a bunch, lots of good reading there- I even asked Doc a question there about the short circuiting 2 strokes do.

A heated wide band would be better but what about reading short circuited oxygen? I don't get how "oxygen only" is short circuited, one would think it would be a mix of raw fuel and oxygen.

An alternative that you might want to consider is http://www.jandssafeguard.com/monitors.html . This device is designed to work with the Bosch LSM 11 sensor . More info on this is available from Dr. Dave Redszus at Precision Automotive Research, at (630) 766-4402

Cool...thanks!

 

[RustyS]

Originally posted by EricGorr
Theres a raging debate about that. Some tuners believe in placing oxygen sensors in the convergence cone of the pipe, others claim it won't work because there is so much raw fuel traveling through a pipe because of short circuiting.
Karters use temperature sensors to monitor exhaust gas temperature to shut the engine down before a seizure occurs. I use an OPTAK, a now defunct company that made a combo EGT/RPM gauge designed for the harsh off-road motorcycle environment. Its very difficult to get a dirt bike up to temperature, and the 1100F target can only be achieved at wide open throttle. When riding enduros through the woods the average EGT is 400-600F measured 6 inches from the exhaust face of the piston.
I advocate the Ride and Feel jetting method, because throttle response is subjective to rider skill.

How did you arrive at the 6" form the face of the piston (that is what I use) since I installed mine at 6" I have read that the probe needs to be installed before the "wet line" in the head pipe so the fresh air/fuel that is drawn into the pipe does not cool the probe and give false readings.

After reading about the 'wet line' I pulled my pipe looking for the wet
line but only found a dry head pipe, then pulled the head and looked into the exhaust port and could see the wet line before the exhaust manifold.

I know each engine will be different and even the same engine will vary when it has been modified, carb, porting, pipe etc.

How important is the location of the probe to get a accurate reading?

From what I have heard the oxygen sensors dont last long because of the oil and rich mixure when the jetting is off or the engine is cold, too bad there was not a way to shield the sensor until the engine was close to operating temperature....

Thanks

 

[EnduroDude]

Originally posted by RustyS
How did you arrive at the 6" form the face of the piston (that is what I use) since I installed mine at 6" I have read that the probe needs to be installed before the "wet line" in the head pipe so the fresh air/fuel that is drawn into the pipe does not cool the probe and give false readings.

I talked with the R&D department at FMF today and was told 3" from the cylinder head/pipe connection. I asked why there and was told that this simply is a standard and would make for readings that are consistent with what everyone talks about.
I asked if I put it much closer like as in racing automotive applications- right in the port... wouldn't the reading be colder from the "short circuit" pulse? and was told that the extreme combustion temps will out weigh that pulse and the probe will not have a chance to cool.

After reading about the 'wet line' I pulled my pipe looking for the wet
line but only found a dry head pipe, then pulled the head and looked into the exhaust port and could see the wet line before the exhaust manifold.

I know each engine will be different and even the same engine will vary when it has been modified, carb, porting, pipe etc.

How important is the location of the probe to get a accurate reading?

My thoughts are VERY important. I have not installed my EGT yet but plan to using a non contact infrared thermometer to located the hottest spot for installation.

From what I have heard the oxygen sensors don't last long because of the oil and rich mixture when the jetting is off or the engine is cold, too bad there was not a way to shield the sensor until the engine was close to operating temperature....

You could by having the port plugged, after warm-up remove the plug and screw in the O2 sensor and zip tie the meter on just for tunning.
Trouble is with a standard O2 sensor reading 12:5 to 1 ratios will be tough because that is near its limit of readability. A wide heated band O2 sensor is whats needed but that would mean having to have a lighting coil for power and the set up is much more spendy thus shifting the idea back to reading EGT.

For now I plan to jet using the ride-n-feel method along with plug color, record that days temperature, humidity, altitude, barometric pressure and dew point using a Kestrel 4000 pocket weather tool.

Next I will install the EGT and read those temps as optimum for my bike & mods.
Re-jetting for different ridding areas will be calculated on the Kestrel, jets changed and then go have fun but during the fun I will monitor the EGT off and on just to see if my jetting calculations were correct by maintaining my previous optimum temps. and if not than a tweak in calculations will be made before I return to the same ridding area.

I am looking for a battery powered LCD to read the EGT's and so far have only found an LED unit that I can use with a 9V battery but that kind will have a short battery life.

 

[EnduroDude]

Originally posted by EricGorr
Theres a raging debate about that. Some tuners believe in placing oxygen sensors in the convergence cone of the pipe, others claim it won't work because there is so much raw fuel traveling through a pipe because of short circuiting.

I too am wondering about that, the added oxygen from that short circuit charge is an unknown variable since most of it is supposed to be pushed back in the combustion chamber. The amount that doesn't I would think is subjective to pipe design & RPM's.

Still if one were to jet by the ride-n-feel method, crossed referenced with plug color and dial it in good there....couldn't one read the O2 "at that time" as optimum for that bike and modifications, then use that O2 number at other ridding elevations to confirm if any changes to jetting for the new area are correct?
Same way one would use EGT.

 

[tzracer46]

I have used the AIM Spped tune O2 sensor setup, and found it to be a very useful tuning tool. Granted my opinion of it might be a bit skewed as I use it on a 2 stroke grand prix roadracing motorcycle, but here's my 2 cents on it. The sensor is mounted in the center section of the pipe, not in the rear cone. I'm not sure how well it would work on a dirtbike as the sensor needs heat to work properly, and it doesn't get really hot at lower rpms which could give a false lean indication. Any way the gauge gives a reading in volts. on a 4 stroke the voltage reading is generally .5-.6 volts if the engine is jetted correctly. on a 2 stroke the ideal range is usually somwhere in the .3-.35 range. The main thing to remember though is that there is no "magic" number that works for all bikes. What you need to do is install the gauge, and run the bike on the dyno and jet the bike until it makes the best power, and then look at the number on the display. Then when you go to the track watch the disply and jet for the number you found on the dyno that gave the best power. Other things you need to take into consideration are fuel type and brand, and oil type, brand and mixture ratio as these will affect the gauge readout. For example on my 2000 TZ250 my ideal number when running VPC12 & silkolene pro 2 mixed at 25:1 my number was 40. When I switched to VP MR8 with the same oil and mixture ratio my number was 44. Hope my insight helps

 

[EnduroDude]

Originally posted by tzracer46
What you need to do is install the gauge, and run the bike on the dyno and jet the bike until it makes the best power, and then look at the number on the display. Then when you go to the track watch the display and jet for the number you found on the dyno that gave the best power. Hope my insight helps

Thanks for the info, my trouble is that I live and play ride at 4-5 thousand feet but when off to the Enduro events the temps and elevation change enough to warrant a jet change.
I thought if I have the jetting spot on at home, then forecast Air Density for the event, make the jet change at home and then use the instrument with a few short warmed up zips to fine tune to the original number I have at home.
Don't have any dynos around here.

My XR400 worked good everywhere, maybe the RM will too, maybe I am just being picky on having jetting right at all the rides.
I suppose its possible to find a compromise set of jetting but then again thats a compromise.