2.5bar SD tune acting pretty weird

[ayousef]

Okay I lost hope trying to figure this out myself so here goes.

I have a 2013 Camaro ZL1 running a closed loop 2.5bar OS, MAF sensor and LTFTs are disabled.

Now assuming I dial in the idle/cruise and coast portions of the VE table using the narrowbands and get them all as close as possible to zero.

What happens is:

1- If the weather gets significantly hotter and more humid (less oxygen in the air) the car actually gets leaner instead of getting richer. In this example the average fuel trims would be -5% on a cold day and get to +7% on the hot day, quite a big swing in the wrong direction. This has been repeatable for quite some time. As a result WOT fueling also gets leaner and I have that measured with my NGK AFX wideband.

2- if the car has been logging positive fuel trims say in the +5% to +7% range and I stop and upload the SAME file into the car, trims instantly swing to an average of say -5%.

All of this doesn't make any sense to me, I do see some AFR swinging when the intake air temps change based on whether im driving on the highway or stuck in traffic, otherwise im confused.

[SultanHassanMasTuning]

Well, first of all your stock map sensors is 3 bar. why would you go Mafless?

[flavorwrench]

I noticed you have the Cylinder Vol. set at 0.87500

[BigDaddyCool]

If you find a solution post it up. It's hard dealing with AFR swings....... mine generally sits around .5 AFR leaner depending on the weather or time of day eg. morning vs night.

I'm rolling at present with my wideband in open loop...... a morning run to work I might run 14.7 pretty stable down the highway, but on the way home around 5-6pm.... sits around 15.2.

This for me occurs in mafless, maf only mode or mixed mode........

[ayousef]

I noticed you have the Cylinder Vol. set at 0.87500

I hope this answers your questions



427 built motor + Whipple 4.0 and dual throttlebodies (ecu sees one throttlebody only)

[ayousef]

If you find a solution post it up. It's hard dealing with AFR swings....... mine generally sits around .5 AFR leaner depending on the weather or time of day eg. morning vs night.

I'm rolling at present with my wideband in open loop...... a morning run to work I might run 14.7 pretty stable down the highway, but on the way home around 5-6pm.... sits around 15.2.

This for me occurs in mafless, maf only mode or mixed mode........

Honestly your problem doesn't sound as bad as mine, my AFR is all over the place. I would upload the exact same file and fuel trims would change, I wouldn't be surprised if AFR moved depending on the time of the day or weather that how SD tunes work, however I expect it to get richer when the weather gets hotter and more humid and leaner when it cools outside and not the other way around.

[flavorwrench]

Holy shit! Well good luck on that one. I suppose starting a thread a thread with "I have a 2013 Camaro ZL1 running a closed loop......" might be a little misleading. I remember seeing pictures of this build a while back on C5 and wondered how one might calibrate that masterpiece. Subscribed, Awesome Work!

[ayousef]

Holy shit! Well good luck on that one. I suppose starting a thread a thread with "I have a 2013 Camaro ZL1 running a closed loop......" might be a little misleading. I remember seeing pictures of this build a while back on C5 and wondered how one might calibrate that masterpiece. Subscribed, Awesome Work!

haha didn't wanna attract too much attention, believe it or not the car is dialed in as nicely as I think is possible without actually being a professional OEM calibrator. I don't know everything but I pick up bits and pieces from here and there and the results have been good. It was definitely a beast to get calibrated, no kidding this car might have 300+ iterations of the calibration lol.

[DRTWRK]

haha didn't wanna attract too much attention, believe it or not the car is dialed in as nicely as I think is possible without actually being a professional OEM calibrator. I don't know everything but I pick up bits and pieces from here and there and the results have been good. It was definitely a beast to get calibrated, no kidding this car might have 300+ iterations of the calibration lol.

You might try logging Air Charge Temp.
I noticed you already have your Cylinder Charge Temperature> Bias table zeroed out. This is also what I have done but I use The Custom OS Main VE>Charge Temp Mult table with as much as a 6.5% swing between 263K and 363K Charge air temps.

This covers variation in temps that we incur here in north Texas. It takes quite a bit of time and patients to adjust for all temp ranges (different times of the year) but was well worth it to realize AFR stability

The VE Charge Temp air multiplier table will do as it says, MULTIPLY your VE table settings by percentage. (Your charge air temps can vary substantially whether your at high speed with plenty of fresh cool air flowing into your intake or sitting in traffic on a 110* day)


I had good results in this table and it really helped out with the large swing in AFR. My AFR will stay pretty stable in all temps now. I also use and log with wide band.