A/F ratio

[ReTodd]

I'm puting a wideband o2 on my Rev this year but have never dealt with 2 strokes and what the optimal ratios are. So, for a NA 800, what ratios should I shoot for in the low/mid/wot bands? Thanks for any input.


Rt

 

[Anylizer]

IMHO... you would be better off using an EGT gauge than O2. The O2 sensors will deteriorate rapidly because of the oil in the exhaust, the sensor gets contaminated and will not read properly. Egt probes ar not effected by the oil. .02 A.

 

[IdahoPowderHound]

they are very accurate monitoring tools but like he said they wont last long. have an Innovate wideband on my 600 turbo and it only lasted me two seasons.....

 

[ReTodd]

they are very accurate monitoring tools but like he said they wont last long. have an Innovate wideband on my 600 turbo and it only lasted me two seasons.....

Really just want it for a season or so, then it won't matter too much. On my TRX1 we wanted to keep the ratio under about 13/1...just need to know if I want to shoot for the same on a 2 stoker.

Rt

 

[EricW]

My T Dragon runs well in the high 12's to low 13's. I'll see 14 or a little more once in a while but try to not have that happen at WOT. I run Innovate as well with th extended bung at 12 o clock in the pipe stinger. No problems yet on 07 700 or 08 800. It is a good idea to keep the gauge as dry as possible. i've seen guys have good luck wrapping it in a baggie. Good luck. EW

 

[ReTodd]

I'm getting an innovative as well....where did you get the xtended bung? (wow, never thought I'd be asking that)

 

[frock]

I'm puting a wideband o2 on my Rev this year but have never dealt with 2 strokes and what the optimal ratios are. So, for a NA 800, what ratios should I shoot for in the low/mid/wot bands? Thanks for any input.


Rt

I have an AEM O2 sensor on mine as well as an EGT and if I could only have one it would be the O2 sensor. I've had mine for one season without any problems and I've already replaced both probes on my Digitron in the same time. It is very responsive and accurate. I run an 06 M7 chassis with a 900 Engine Tech in it and I see anywhere up to 14.5 - 15% excess O2 at low, 13.5 - 14% at mid and 13% max at WOT (this is the very edge for mine at WOT), 12.5% is much safer at WOT.

 

[ReTodd]

Sounds like the same ratios I ran on my TRX1. I like a lean mid for quicker reving but like to run her closer to 12.5 for those long slow WOT pulls in bottomless snow.

 

[AndrettiDog]

I'm looking for the article, but I read 13:1 was the magic number. I'll post if I find that article.

 

[Reeb]

got one in a box right now. Going to try that over my Digi. With the problems I've had with it, I got a dual KOSO and a 02 AEM this season. Any tips to installation or tips to making them last longer?

 

[Reeb]

Gotta subscribe.

 

[EricW]

On a non-turbo I have been told to mount the sensor in the pipe stinger at 12 o'clock prior to the can. On a turbo'd sled it goes after the unit in the down pipe. I can't find a pic of the o2 in my turbo.

This is the stock location

This is a spare bung and plug that I mounted so the sensor isnt in the pipe when I'm not tuning. Just pull the sensor from the pipe and the cap from the spare bung and switch 'em. Sensor stays stored nice and plug caps off the extended bung. I have had great luck with this as you don't need the thing very often once tuned for altitude/conditions, just takes a sec to switch if you do. I think most of the fouling issues come from all the start up and idleing/loading. If the sensor is in the exhaust stream only when your actually tuning I think it helps a bunch and I'm a pretty fart smeller / smart feller. THIS is the spare bung/plug. THIS is the HBX bung extender.

 

[76FOMOCO]

now this is some GREAT INFO!!! dude your are the cutest fart smeller so far! Thanks.

 

[EricW]

now this is some GREAT INFO!!! dude your are the cutest fart smeller so far! Thanks.

I'm not exactly a brain surgeon, but I am in the medical field......lol

 

[frock]

I like your probe holder idea there EW, very innovative.

I have a single BMP y-pipe, pipe and can on my 900 ET and I mounted my O2 sensor right on the top of the can. It's worked great so far. I use my EGT to confirm my O2 numbers and it's been very accurate and reliable so far.

 

[scarter]

I would recomend 14.7-15.5 in the low and mid RPM ranges. Most of your stock ECU programs for fuel injected sleds are 15.5/1 or leaner for emissions in the midrange. I have found the best throttle response to be around 15/1 in the midrange. I run 12.7 or less at WOT. When it comes to WOT I still check Plugs and pistons for the last word.

The numbers on your A/F guage are an Air to Fuel ratio not a percent excess oxygen.

 

[sanjuansledhead]

14.7 is considered perfect burn or "stoic condition" for gas engines ,that number should not fluctuate w/ boost or octane rateing after inital tuning. How ever changes in boost or altitude will have bearing on this number. One will want to dial in stoic at high load and w.f.o., Also, In A sled you may want to find a guage with tattle tale or memory.

 

[skibreeze]

14.7 is considered perfect burn or "stoic condition" for gas engines ,that number should not fluctuate w/ boost or octane rateing after inital tuning. How ever changes in boost or altitude will have bearing on this number. One will want to dial in stoic at high load and w.f.o., Also, In A sled you may want to find a guage with tattle tale or memory.

Try that in your own sled and then get back to us. Don't forget to bring a friend...... and a tow rope.

 

[scarter]

I am with Skibreeze on this one. A two stroke won't last very long at w.f.o. tuned to 14.7.

And secondly stoich doesn’t change with altitude or boost. It’s a ratio of air molecules to fuel molecules. It does change with types of fuel but that is another topic.

 

[Skinner]

These are the numbers I got from SLP for the M1000. Should be close. Ran them last year and the sled ran Great all year.

Idle: 14-1 to 16-1



Low load part throttle (up to 50% throttle opening) 14-1 to 15-1



Low load part throttle (50 to 65% throttle opening) 13.5-1 to 14-1



High load above 65% throttle opening: 12.2-1 to 13.2-1



The M-1000 can run on the leaner side of these numbers if not leaner. You will need to determine that with plug checks and piston wash.



Thanks,