A/F (Air/Fuel) Ratio - Toyota Yaris Forums

Kaotic Lazagna · 09-11-2012, 10:18 PM

At idle and cruising/very light acceleration, my A/F ratio (according to my SG) stays around stochiometric (14.5), but when I floor it (only tried flooring it in 2nd gear starting from ~10mph and in 5th gear starting from ~32mph), it goes to 15-17. That means I'm running lean when I'm flooring it. It should be going <14, right? That means my engine isn't getting enough fuel when I'm flooring it (car doesn't bog or anything, and actually accelerates decently despite my wheel and tire combo being 41.3 lbs). Maybe it's because of where I am in the rpm band when I was flooring it? I was in city streets, so maybe that's why? I'll try flooring it on the freeway in 3rd gear the next time I'm on the freeway. There were a couple of times that it briefly went to 12.8.

I also noticed that if the loop remained closed, and when I was flooring it, that's when it went to 12.8. As soon as the loop went to open, the AF ratio went to 15-17.x.

Should I be concerned about this, or not because I'm basing it off the Scan Gauge, and I'm not too sure where it's getting its readings from.

Kaotic Lazagna · 09-11-2012, 10:21 PM

Mods include K&N SRI (intake pipe and engine side of heat shield wrapped in heat reflective material, if that makes a difference), 2.25" resonator-back exhaust, and NST CR-Lite crank pulley.

Kaotic Lazagna · 09-11-2012, 10:29 PM

More info, I'm using this X-Gauge

Air to Fuel Ratio for CANSF vehicles
GAUGE: A/F Ratio Bank 1 - Sensor 1
TXD: 07DF0124
RXF: 044145240000
RXD: 2808
MTH: 05B900800000
NAME: A/F
note: Ratio of Air to Fuel

eTiMaGo · 09-11-2012, 11:19 PM

From my own experience the Scangauge shows you the "target" AFR of the ECU, not the actual ratio detected by the sensor. SO when it goes open-loop, there's no need for a target AFR and it may show a junk value...

Kaotic Lazagna · 09-11-2012, 11:40 PM

Thanks Thomas! So I'm going to assume that my car does go to being on the rich side when I floor it based on the very brief times it goes to 12.8 while still on a closed loop (so the ECU is making an effort to get the AF ratio there).

CTScott · 09-11-2012, 11:51 PM

Thomas is correct - That is target AFR, as opposed to actual AFR. I can read both with my YarGauge, and they are seldom in the same range. Also, the ScanGauge is pretty slow to poll the ECM, so the data lags quite a bit.

Kaotic Lazagna · 09-12-2012, 12:00 AM

Quote:

Originally Posted by CTScott

Thomas is correct - That is target AFR, as opposed to actual AFR. I can read both with my YarGauge, and they are seldom in the same range. Also, the ScanGauge is pretty slow to poll the ECM, so the data lags quite a bit.

So, with those number that I saw, my car is pretty normal then?

CTScott · 09-12-2012, 12:01 AM

Quote:

Originally Posted by Kaotic Lazagna

So, with those number that I saw, my car is pretty normal then?

Yes. They are normal for target. But, again that really doesn't mean much.

Kaotic Lazagna · 09-12-2012, 12:25 AM

Quote:

Originally Posted by CTScott

Yes. They are normal for target. But, again that really doesn't mean much.

Ah, I guess I'll just delete that gauge. Thanks, Thomas and Scott.

eTiMaGo · 09-12-2012, 09:05 AM

yeah I stopped looking at it pretty quickly too... maybe on some other cars it shows more meaningful information, who knows...

And I don't know if your car does the same as mine did, but you could tell when it's running rich in open loop by the smell that starts to permeate the cabin :D

Kaotic Lazagna · 09-12-2012, 01:50 PM

Quote:

Originally Posted by eTiMaGo

yeah I stopped looking at it pretty quickly too... maybe on some other cars it shows more meaningful information, who knows...

And I don't know if your car does the same as mine did, but you could tell when it's running rich in open loop by the smell that starts to permeate the cabin :D

lol, I thought that was the older car that was traveling in front of me when I was doing the testing. Yeah, I don't ever floor it in such a low rpm

Don't smell anything if I floor it on the freeway tho.

09-11-2012, 10:18 PM	#1
Kaotic Lazagna View User's Garage Drives: '14 GT86, '08 Vitz Join Date: Dec 2006 Location: Central Valley, CA Posts: 9,873	A/F (Air/Fuel) Ratio At idle and cruising/very light acceleration, my A/F ratio (according to my SG) stays around stochiometric (14.5), but when I floor it (only tried flooring it in 2nd gear starting from ~10mph and in 5th gear starting from ~32mph), it goes to 15-17. That means I'm running lean when I'm flooring it. It should be going <14, right? That means my engine isn't getting enough fuel when I'm flooring it (car doesn't bog or anything, and actually accelerates decently despite my wheel and tire combo being 41.3 lbs). Maybe it's because of where I am in the rpm band when I was flooring it? I was in city streets, so maybe that's why? I'll try flooring it on the freeway in 3rd gear the next time I'm on the freeway. There were a couple of times that it briefly went to 12.8. I also noticed that if the loop remained closed, and when I was flooring it, that's when it went to 12.8. As soon as the loop went to open, the AF ratio went to 15-17.x. Should I be concerned about this, or not because I'm basing it off the Scan Gauge, and I'm not too sure where it's getting its readings from.

09-11-2012, 11:19 PM	#4
eTiMaGo vroom vroom View User's Garage Drives: lil red 5-door Join Date: Sep 2006 Location: Bangkok, Thailand Posts: 7,744	From my own experience the Scangauge shows you the "target" AFR of the ECU, not the actual ratio detected by the sensor. SO when it goes open-loop, there's no need for a target AFR and it may show a junk value... __________________ The price of freedom of religion, or of speech, or of the press, is that we must put up with a good deal of rubbish. - Robert Jackson Bye bye 1NZ...

09-11-2012, 11:51 PM	#6
CTScott ULTIMATE View User's Garage Drives: 09 5dr LB, 2x 08 3dr LB Join Date: Oct 2008 Location: USA, CT Posts: 13,460	Thomas is correct - That is target AFR, as opposed to actual AFR. I can read both with my YarGauge, and they are seldom in the same range. Also, the ScanGauge is pretty slow to poll the ECM, so the data lags quite a bit. __________________

09-12-2012, 09:05 AM	#10
eTiMaGo vroom vroom View User's Garage Drives: lil red 5-door Join Date: Sep 2006 Location: Bangkok, Thailand Posts: 7,744	yeah I stopped looking at it pretty quickly too... maybe on some other cars it shows more meaningful information, who knows... And I don't know if your car does the same as mine did, but you could tell when it's running rich in open loop by the smell that starts to permeate the cabin :D __________________ The price of freedom of religion, or of speech, or of the press, is that we must put up with a good deal of rubbish. - Robert Jackson Bye bye 1NZ...

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09-11-2012, 10:21 PM	#2
Kaotic Lazagna View User's Garage Drives: '14 GT86, '08 Vitz Join Date: Dec 2006 Location: Central Valley, CA Posts: 9,873	Mods include K&N SRI (intake pipe and engine side of heat shield wrapped in heat reflective material, if that makes a difference), 2.25" resonator-back exhaust, and NST CR-Lite crank pulley.

09-11-2012, 10:29 PM	#3
Kaotic Lazagna View User's Garage Drives: '14 GT86, '08 Vitz Join Date: Dec 2006 Location: Central Valley, CA Posts: 9,873	More info, I'm using this X-Gauge Air to Fuel Ratio for CANSF vehicles GAUGE: A/F Ratio Bank 1 - Sensor 1 TXD: 07DF0124 RXF: 044145240000 RXD: 2808 MTH: 05B900800000 NAME: A/F note: Ratio of Air to Fuel

09-11-2012, 11:40 PM	#5
Kaotic Lazagna View User's Garage Drives: '14 GT86, '08 Vitz Join Date: Dec 2006 Location: Central Valley, CA Posts: 9,873	Thanks Thomas! So I'm going to assume that my car does go to being on the rich side when I floor it based on the very brief times it goes to 12.8 while still on a closed loop (so the ECU is making an effort to get the AF ratio there).