A/F ratios inconsistent

davelaub25 · Post by **davelaub25** » Sun Sep 13, 2009 1:38 pm

I'm new to this board and fairly new to tuning as well. I was wondering if any one has experienced very inconsistent A/F readings. I've ruled out the sensor itself. The engine I'm practicing on is a stock B16 w/IHE. I thought it would be easy to start with being the stock maps should be close to what I need. That's not the case though. I ride around logging AFR on the map and get one set of readings then make another run without changing anything and get a completely different set of readings. Any ideas on what could cause this?? I was thinking an exhaust leak, but haven't had any luck finding one. The other possibility I was considering was fuel pressure. There is a walbro in the tank, with a FP regulator holding the pressure at about 30psi @ 24 inches of vacuum. The pressure rises as the vacuum drops but its hard to see whats going on during driving because the gauge is under the hood. Any suggestions are appreciated. Thanks in advance.

Almighty-Si · Post by **Almighty-Si** » Sun Sep 13, 2009 2:25 pm

Did you adjust battery offsets, ect/iat corrections?

davelaub25 · Post by **davelaub25** » Sun Sep 13, 2009 2:49 pm

I think I did the offsets correctly. I adjusted them so that it Idled at the same afr no matter what voltage the battery was at by turning on and off various accessorys. I havent really touched the ect/iat compensation. I kind of assumed the stock settings would suffice. Anywhere I can read about proper way of setting them?

xenocron · Post by **xenocron** » Sun Sep 13, 2009 6:39 pm

Almighty-Si wrote:Did you adjust battery offsets, ect/iat corrections?

Why would he have to adjust any of these on a stock motor with I/H/E?

davelaub25 · Post by **davelaub25** » Sun Sep 13, 2009 9:22 pm

That's why I started with this motor. I figured it would be easier than jumping right into a highly modified motor with larger injectors and increased compression and displacement. It seems to me that there might be something else going on. Any ideas?

ninezeroteg · Post by **ninezeroteg** » Sun Sep 13, 2009 9:30 pm

How much of an inconsistency are we talking about here? Some inconsistencies are to be expected due to ambient air temps, barometric pressure changes, etc...

davelaub25 · Post by **davelaub25** » Sun Sep 13, 2009 10:06 pm

Well here's an example. 1st full throttle run AFRs around 13.4-13.7 Next attempt no changes I wind up leaning out to about 14.3. So I guess almost a full point.

ckretvix · Post by **ckretvix** » Sun Sep 13, 2009 10:22 pm

Sure your wideband doesnt have a bad ground/is calibrated correctly?

Almighty-Si · Post by **Almighty-Si** » Sun Sep 13, 2009 10:43 pm

xenocron wrote:Why would he have to adjust any of these on a stock motor with I/H/E?

The settings never worked for me, I always had to adjust them to get the car to idle properly after driving for a bit.

davelaub25 · Post by **davelaub25** » Sun Sep 13, 2009 10:53 pm

ckretvix wrote:Sure your wideband doesnt have a bad ground/is calibrated correctly?

I've checked that it's calibrated. I hadn't thought to see if it was a grounding issue. I do have a ground loop in the electrical system somewhere. You can hear what I assume is the fuel pump through the speakers. Could that cause problems with other electronics?

xenocron · Post by **xenocron** » Mon Sep 14, 2009 7:54 am

Almighty-Si wrote:
xenocron wrote:Why would he have to adjust any of these on a stock motor with I/H/E?
The settings never worked for me, I always had to adjust them to get the car to idle properly after driving for a bit.

Calvin, any insight on this? I would say there should be ZERO that needs to be changed in the correction stuff...these are all set at the factory and since all of this stuff is based on factory code, there should only be a need to fiddle with the main fuel and ignition maps.

xenocron · Post by **xenocron** » Mon Sep 14, 2009 7:56 am

davelaub25 wrote:
ckretvix wrote:Sure your wideband doesnt have a bad ground/is calibrated correctly?
I've checked that it's calibrated. I hadn't thought to see if it was a grounding issue. I do have a ground loop in the electrical system somewhere. You can hear what I assume is the fuel pump through the speakers. Could that cause problems with other electronics?

Post logs that show these inconsistancies along with the calibration and you'll def be able to get more help. Look at everything thats going on thats DIFFERENT in each run and draw certain conclusions based on those differences. Work out AS MANY of these issues and inconsistancies you can on the street first, and then get the car on a dyno where you can hold other factors consistant along with being able to watch fuel pressure and other things along those lines.

davelaub25 · Post by **davelaub25** » Mon Sep 14, 2009 12:30 pm

Thanks for the advice. When setting up the fuel correction tables I followed this order: 1. Let the car fully warm up. Set fuel map so the car idles around 14.7 2. Let the car cool off then start back up 3. While the car is warming up adjust fuel correction for ECT/IAT so that the car holds the same AFR during the warm up process. 4. Turned on various accessories to change battery voltage and watch AFR to see if inj. offset needs to be adjusted. Does that sound correct? I'll try to get some logging in after work today. This morning before I left for work I had the laptop hooked up during warm up. The AFRs swung from 13.6 to 14.3. I tried to see what had changed but I was unsuccessful. To me it seemed that none of the readings changed enough to bump from one cell to the next on ECT and IAT as well as battery offset. Are the values in these tables interpolated?

xenocron · Post by **xenocron** » Mon Sep 14, 2009 1:39 pm

I make the basemap and start the car let it warm fully (with no other corrections), get it to idle around 13.5-14.0 or wherever it will idle the MOST stable without changing anything else. Then I turn on ALL accessories possible trying to get the voltage to go down, might even unhook the Alternator cable from the fuse box if I am feeling crazy and get the AFRs to stay as stable as possible or possibly go a little richer and thats ok (but not leaner, if your Alt ever fails you want the battery table to compensate too rich if anything). Then I tune the car fully then. And then if time permits let the car cool fully, and THEN play with the ECT warmup tables, cranking trims, etc...generally they are pretty close though.

davelaub25 wrote:Thanks for the advice. When setting up the fuel correction tables I followed this order: 1. Let the car fully warm up. Set fuel map so the car idles around 14.7 2. Let the car cool off then start back up 3. While the car is warming up adjust fuel correction for ECT/IAT so that the car holds the same AFR during the warm up process. 4. Turned on various accessories to change battery voltage and watch AFR to see if inj. offset needs to be adjusted. Does that sound correct? I'll try to get some logging in after work today. This morning before I left for work I had the laptop hooked up during warm up. The AFRs swung from 13.6 to 14.3. I tried to see what had changed but I was unsuccessful. To me it seemed that none of the readings changed enough to bump from one cell to the next on ECT and IAT as well as battery offset. Are the values in these tables interpolated?

davelaub25 · Post by **davelaub25** » Mon Sep 14, 2009 2:28 pm

I'll try that tonight. I'll start from scratch (again) and follow that order. I hope this isn't asking too much but is there any way someone could post a datalog of a properly running car? One that is tuned and behaving properly. I'd like to look at it to get an idea of what I should expect to see. Again, thank you everyone. All your help is appreciated.