Wideband users: AFRs while driving normally?
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TECH Resident
Joined: Jan 2004
Posts: 832
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From: Castro Valley, CA
Wideband users: AFRs while driving normally? If I watch my wideband gauge, it's all over the place in the lean areas (13-17)while I'm driving normally, cruising on the freeway with very low throttle in fifth or sixth at probably 1500-2100 rpm, no boost. Actually, if I look at the boost gauge it reads -19 (vac) with no throttle and maybe -10 (vac) or so with maybe 10% throttle. As soon as I tip into the throttle and accelerate, AFRs head down where they should be ~12. Once in boost all is well, flat at ~11.5.
I haven't worried about these seemingly VERY lean readings because I thought it was just a by-product of how the wideband sensor reads under very low loads... but I'm not sure. The car is speed density tuned.
Thoughts/opinions? Do I need to worry about this?
I haven't worried about these seemingly VERY lean readings because I thought it was just a by-product of how the wideband sensor reads under very low loads... but I'm not sure. The car is speed density tuned.
Thoughts/opinions? Do I need to worry about this?
11 Second Club
Joined: Oct 2006
Posts: 149
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Is it an open or closed loop tune? If closed loop the switching from rich to lean under cruise is normal as the PCM responds to the narrowband input. If you have an open loop tune there could be an issue with the VE table.
When I cruise my AFR stays around 14.5-14.9. Very rarely do I see 15+ unless I am decelerating. I don't hit richer AFRs unless I enter PE mode, which I have left at stock parameters.
At closed loop there is a proportional fueling that bangs
the AFR around on purpose so the O2 voltages will swing
over center. You are seeing this most likely. If you increase
the filtering of the WBO2 voltage it will average things to
14.7ish just like the PCM is doing, you just can't look too
close as you pass through the sausage factory.
the AFR around on purpose so the O2 voltages will swing
over center. You are seeing this most likely. If you increase
the filtering of the WBO2 voltage it will average things to
14.7ish just like the PCM is doing, you just can't look too
close as you pass through the sausage factory.
Remember too that under about 4000rpm, acceleration enrichment tips in when you accel or even start going up a hill with no TPS change, so your mixture will clearly be different at 45mph under accel as opposed to 45 steady state.
On my Vortech-blown 383, I have been tuning for light load AFR's around 15.50. If I datalog a light accel from 60 to 80, I'll record AFR's around 12.75-13.25 until I finish the accel. Above 4Krpm, there generally is no Accel Enrichment that happens, even when you accel. It's all fuel map and VE tables if you have them. I'm using a Holley 950 Pro with FJO Racing wideband.
Jim
On my Vortech-blown 383, I have been tuning for light load AFR's around 15.50. If I datalog a light accel from 60 to 80, I'll record AFR's around 12.75-13.25 until I finish the accel. Above 4Krpm, there generally is no Accel Enrichment that happens, even when you accel. It's all fuel map and VE tables if you have them. I'm using a Holley 950 Pro with FJO Racing wideband.
Jim
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Joined: Nov 2001
Posts: 2,659
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From: Bellevue, Wa
I think the key is open or closed loop.
If it's open unless your tuner spent a crapload of time driving the car around then likely the VE table isn't quite right. Could be other variables as well, just picking on VE.
Even if he did drive around, SD Open Loop will, at least in my experience, as well as others I know, always be all over the map under light load.
Do you really need to stress over it? Likely not. You may be able to get some better gas mileage with a bit of work but as for engine damage, it sounds like your covered as you say your getting into boost / WOT tuning seems fine.
Take it back to your tuner and see what he says, I would think he will fix it for free since it left not quite right, then again maybe not. Don't know what you guys agreed upon as acceptable results from the tune.
If it's open unless your tuner spent a crapload of time driving the car around then likely the VE table isn't quite right. Could be other variables as well, just picking on VE.
Even if he did drive around, SD Open Loop will, at least in my experience, as well as others I know, always be all over the map under light load.
Do you really need to stress over it? Likely not. You may be able to get some better gas mileage with a bit of work but as for engine damage, it sounds like your covered as you say your getting into boost / WOT tuning seems fine.
Take it back to your tuner and see what he says, I would think he will fix it for free since it left not quite right, then again maybe not. Don't know what you guys agreed upon as acceptable results from the tune.
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