AFRs are rich at operating temp.... 15 min later they are LEAN... what is going on??

[TXjeepTJ]

About to quit tuning all together, I CANNOT tune the VE table for the life of me. I have been trying to tune it on/off for the past 3 years..

Anyways, I just attempted to tune VE again.. I made sure MAF isn't working, as I made the MAF table all zeros. Car still runs and PO103 shows.

I started the car, let it get up to operating temp 190 degrees (I have 160 thermostat) and started logging. The first half of the trip many cells were rich. At idle, my AFR error was NEGATIVE 10. After driving up the highway a few miles and coming back, sitting at a light I saw that now my idle was showing 15.1 AFR (was initially showing 13.7ish)... what would cause this!!?!?!?!?! Pretty much all values that were initially RICH started slowly moving towards LEAN

Log file and tune attached..

Could my wideband be screwing up due to all the heat? This is a single turbo car, 2 bar MAP, my wideband is located about a foot behind the turbo. Something that makes me thing this could be the issue is, I had an issue where the car would stall when going into reverse. I noticed it was going lean, and richening up the 400rpm column solved the issue. Now, after driving for this log file - I pulled into the driveway and saw the idle at 15.1+ AFR. Shifting from park to drive/reverse did not make the car die at all - when before it WOULD die due to it being lean. IDK, this has just been a nightmare experience lol

Chevelle 7-27-2018_6-48pm FLASHED.hpt
Log File 1.hpl

[kingtal0n]

Yes if the wideband is too close to the turbine the high temperature 1000*F+ will cause false rich readings. I've had an AEM unit tell me 11.8:1 when it was 15:1 around 1500*F before I knew better.

Normal operating will cause a small drift from 400*F to 800*F there may be slight difference. I would suggest move it as far away from the heat as possible. A Dyno wideband works just fine at the tailpipe.

Typically less than 5% wander due to normal temperatures.

It is more likely that your voltage at the ECU or injectors is fluctuating, or that your fuel trims need adjusting, especially if you have large injectors and a rough injector delay vs voltage graph. As things warm up, resistance increases everywhere in all electronics, which means lower voltage, which means the same injector on-time as before now gives you less fuel. A large injector like an 1000cc/min as little as .250ms (1/4 of a millisecond) can change the a/f a whole point, especially when the injector is operating near its minimum-pulse-limit.

It is also possible you have active fuel trims. Make sure you are logging all the fuel trims.

I'd say:
1. move the wideband 3-4 feet from turbine like the instructions tell you when you buy one (most say this)
2. make sure all fuel trims are disabled
3. ensure good voltage and good grounds for systems, especially ECU constant power and high quality alternator voltage output signal, make sure voltage isn't fluctuating
4. You can try to smooth the injector delay tables some

If nothing seems to work you can always use the IAT/AFR tables to add fuel when things get hot. There are a couple ways to get creative here as well with IAT placement.

Finally a couple thoughts. the fuel pump pressure could be dropping as the pump wiring heats up (resistance=less volts=less pump head). You wouldn't notice this unless you were logging fuel pressure I suppose.
Something like a filter that "clogs more" as it warms up could also explain this.
Another thing to consider is the 'loading' phenomenon of a combustion engine, where fuel may "hang around" from event to event, showing a rich condition, causing you to remove fuel from the basemap. And then finding out later after running the engine hard, fully warming the port and valves, that now the engine is lean because the ports/valves are too hot to support un-vaporized fuel which no longer enrichens the mixture from cycle to cycle. Some plenums also "fuel share" through the manifold, before often factory injector timing puts fuel on the valve where it vaporizes up into the plenum, at low rpms (and especially with a big cam) you can get a fair amount of fuel traveling up a plenum runner from one event to the next, especially with the reversion of large cam.

[mymonte666]

What type of fuel system are you running? I ask because hotter fuel will be less dense ie less fuel per pulse is goint to be delivered. I had ran into similar issues tunning megasquirt. One car was the iat sensor getting heat soaked due to its location on an aluminum intake manifold. Fixed it by movin the sensor to the charge pipe. The other was bacause of running a small fuel cell with 2 aeromotive a1000's. The system was constantly moving large amounts of fuel to the engine bay, picking up heat and bringing it back to the cell. This issue was resolved for the most part with a fuel cooler.

Check you iat and coolant temp corrections to see if they math your error. I consider a 160 thermostat a bit low imo. In a chevelle you probably have a pretty hefty radiator on there. If your warmed up temperature is barely just getting met, when that thermostat opens that rush of cooler fluid migh be enough to kick you off from your warmed up temp and bounce you back and forth between open and closes loop.
I have seen too cold plugs exhibit similar behaivior too.

Take it with a grain of salt. I am still learning hpt, but have quite a bit of xp with standalones.

[scoob8000]

Where is your IAT? I've read about turbo guys putting it in the intake, and disabling complex model. (tells the PCM to only look at the iat). Just putting it out there to give you some google material.

I chased my tail almost all summer on a NA car trying to tune my VE. I started in the morning when it was cooler, and as the day got hotter it kept correcting leaner, and leaner. Turns out it was the cylinder charge temp screwing me up. It can bias towards the ECT or towards the IAT. Soon as I saw my intake air temp hit 90, it was day and night difference on the AFR error. After sitting and it heat soaking at a red light, I was nearly 10-15% lean.

I agree with mymonte on the fuel temp too. I noticed as it would pick up heat, it would get lean. I 'm speculating, but I think they may be trying to compensate with the charge temp bias tables on cars with return vs return less fuel systems just comparing stock files. It would make sense to me that a returnless system has more time to heat the fuel since it's not recirculating back away from the hot engine.

[kingtal0n]

I looked through my 411 gen3 programming and I couldnt find any IAT or CTS related fuel corrections for when it isn't in PE mode. Maybe I missed it though...

[anniversaryss]

I looked through my 411 gen3 programming and I couldnt find any IAT or CTS related fuel corrections for when it isn't in PE mode. Maybe I missed it though...

Cylinder charge temp or somthing like that.
Theres a Bias and cant remember the second one off hand.
Basically it's kind of a tipping point as to how the fuel corrections are "bias" to.
More for the IAT or more for the ECT.
Scoob had an issue where he would tune to an acceptable error. Then a few munutes later or later in the afternoon when it got hotter and IAT went up he would show way lean.

[scoob8000]

I looked through my 411 gen3 programming and I couldnt find any IAT or CTS related fuel corrections for when it isn't in PE mode. Maybe I missed it though...

I'm not sure if it functions differently in PE vs not (I think it affects everything based on my results), but the table I'm referring to is under Engine > General.

It's also based on airflow, so you could have less correction at higher airflow values.

[lukearmstrong1990]

cylinder charge temperature "complex model" switch under ENGINE>AIRFLOW>GENERAL.

switching it to disabled will make the PCM use only the IAT for fueling corrections instead of an altering bias of influence power between IAT and ECT

[PAPz06]

Did you learn what your solution was? I am having, what seems like, the exact same issue. If you have anything to share about it, I'd appreciate it.

About to quit tuning all together, I CANNOT tune the VE table for the life of me. I have been trying to tune it on/off for the past 3 years..

Anyways, I just attempted to tune VE again.. I made sure MAF isn't working, as I made the MAF table all zeros. Car still runs and PO103 shows.

I started the car, let it get up to operating temp 190 degrees (I have 160 thermostat) and started logging. The first half of the trip many cells were rich. At idle, my AFR error was NEGATIVE 10. After driving up the highway a few miles and coming back, sitting at a light I saw that now my idle was showing 15.1 AFR (was initially showing 13.7ish)... what would cause this!!?!?!?!?! Pretty much all values that were initially RICH started slowly moving towards LEAN

Log file and tune attached..

Could my wideband be screwing up due to all the heat? This is a single turbo car, 2 bar MAP, my wideband is located about a foot behind the turbo. Something that makes me thing this could be the issue is, I had an issue where the car would stall when going into reverse. I noticed it was going lean, and richening up the 400rpm column solved the issue. Now, after driving for this log file - I pulled into the driveway and saw the idle at 15.1+ AFR. Shifting from park to drive/reverse did not make the car die at all - when before it WOULD die due to it being lean. IDK, this has just been a nightmare experience lol

Chevelle 7-27-2018_6-48pm FLASHED.hpt
Log File 1.hpl

[kingtal0n]

I put a 1000ohm variable resistor inline with the IAT so when the engine/sensors/injectors heat soak and the engine starts to lean out I just turn the dial add some ohms and problem solved

Even with the heat soaking in open loop the a/f values top out around high 16's engine still runs normal, so take it or leave it, sometimes I turn the dial sometimes I don't even bother.

[dsmdoctor]

https://ls1tech.com/forums/pcm-diagn...eo-guides.html

[smokeshow]

I put a 1000ohm variable resistor inline with the IAT so when the engine/sensors/injectors heat soak and the engine starts to lean out I just turn the dial add some ohms and problem solved

Even with the heat soaking in open loop the a/f values top out around high 16's engine still runs normal, so take it or leave it, sometimes I turn the dial sometimes I don't even bother.