Wideband reading 14.2 at crusing

[Dainslaif]

I recently got my wideband hooked up to my car (Innovate LC-1). Ever since I started data logging, at cruise/idle I'm commanding 14.7 but the car hovers around 14.2 AFR, but at WOT it drops down to what I'm commanding (11.8ish). I don't know what would be causing it for sure.

My plan is to put the car into Open Loop / SD mode and tune the VE table by AFR error, then after I get that right around 14.7, go back to closed loop and retune the MAF by fuel trims (or AFR error, both should work assuming I get the VE table right).

Does that sound right, or am I on the wrong track?

Thanks.

[talsayed]

Read this first,it'll help to set AFR wide band meter (whether LC-1,LM-1 or LM-2) [more or less properly].

http://www.hptuners.com/forum/showthread.php?t=22537

http://www.hptuners.com/forum/showthread.php?t=22400

[Dainslaif]

Yep, I did that already, I also recalibrated the wideband just to make sure it wasn't simply reading off. Just to double check I went and plugged the LC-1 into my computer and ran logworks side by side with HPT and the numbers were the exact same, so it's not offsets. Thanks for the suggestion though.

[Stalker L-67]

A HPT guy commented on one of my posts asking pretty much the same question, he said the MAF system is only good to +-.5%. So there you go, that explains the 14.2.

I have also found that raising the histogram count (which ever one your using to calc your AFR error) up to say 10, REALLY helps get you get dialed in. Dont know if that will help in your case but it makes a big difference. Recently I was able to get +-2% using 8 counts.

Hope this helps.

[Dainslaif]

Yeah, I always worked with >10 or 20 hits on my histos, but thanks for the sanity check

I spoke to dont_blink directly (someone with a lot of experiencing tuning an LSJ) and he told me what I was doing wrong before. When I was tuning the MAF by fuel trims I was using the Sensor LTFT to populate the histogram. I'm not sure what that actually is, but there's also a PID for Long Term Fuel Trim, and that was what I should have been using. I ran it on my last log and it read rich across the board, while the Sensor was close to 0.

So, in short, my VE and MAF tables were way off. I guess my previous tuner just wanted to get my car running, and didn't spend any time actually getting the AFR dialed in.

[S2H]

A HPT guy commented on one of my posts asking pretty much the same question, he said the MAF system is only good to +-.5%. So there you go, that explains the 14.2.

I have also found that raising the histogram count (which ever one your using to calc your AFR error) up to say 10, REALLY helps get you get dialed in. Dont know if that will help in your case but it makes a big difference. Recently I was able to get +-2% using 8 counts.

Hope this helps.

.5% is not going to be the difference of 14.7~14.2

[S2H]

heres my cleaned up post of how to correct for offset voltage..

I actually wrote one of these back in 2004....but this was the most recent one I could find with pictures..

http://www.hptuners.com/forum/showpo...4&postcount=1t

[dont_blink]

It's not the sensor causing the issue. It's just the fact that the car needs tuning.

[Dainslaif]

heres my cleaned up post of how to correct for offset voltage..

I actually wrote one of these back in 2004....but this was the most recent one I could find with pictures..

http://www.hptuners.com/forum/showpo...4&postcount=1t

I mentioned before it's not offset voltage. I even went into Logworks (which has no voltage offsets) and compared them side by side - they were equal.

I'm thinking at this point it's a bad WB O2 sensor or an exhaust leak.

[BeermanSS/SC]

exhaust leak would cause lean readings not rich.

[talsayed]

Read this:http://www.hptuners.com/forum/showthread.php?t=22574

[S2H]

exhaust leak would cause lean readings not rich.

actually an exhaust leak would cause it to add fuel....
it cause a false lean reading which the pcm interprets as being too lean....
and then it adds fuel.....which leads to a Rich condition...

but his issue is not an exhaust leak..

[Dainslaif]

exhaust leak would cause lean readings not rich.

Actually, if it was leaking before the factory O2 (which is what I meant and engineer detailed), it would probably add enough to raise it back up to stoich, but it should still read 14.7 on both since there shouldn't be a difference in reading between the two.

It's not the tune either as far as I can tell, although I am getting concerned with the VE table (which is being tuned solely off fuel trims). It's far lower than anyone else's I've seen with similar mods (though to my credit I don't think I've seen a car with a tuned VE table, so it may just be theirs).

At this point I'm pretty convinced it's either the wideband O2 sensor itself or some non-sensor factor involving the factory O2 (since it seems to be pushing the correct AFR at WOT). I picked up a new WB sensor that I'll put in tomorrow and see if the readings are any different, and if that doesn't fix it I'll probably see if I can find an O2 extension and switch bungs around to see if the air just isn't mixing up enough before hitting the primary O2 or something.

[TT_Vert]

Did you figure this out? I have the opposite, reads lean 15.8-16.4@ part throttle unless I put it into open loop, then it is right around commanded. WOT AFR is perfect where commanded.

Dave

[Blizzard242]

Reviving an old thread but I have almost the same exact issue as TT_Vert. I believe I have an exhaust leak after my stock o2 sensors but before my wideband. I'm in the process of fixing this leak but till then, has anyone figured any of this out and maybe the cause isn't a leak?