VE table tuning IAT compensation?

[Xjas]

When tuning my VE table I did two runs on different days and found my VE table pretty close on the first run but the second run I had about an 8-10C increase in average IAT temp and the VE AFR error was lean by around 5% over most of the table.
How do I adjust for this change in IAT?
Do I make changes to the cylinder charge temp bias and filter? If so how do I work out what changes to make.
Or should I be changing the Flow Rate Modifier vs IAT table?

[cgibs60]

That's what long term fuel trims are for. A 5% swing either way is fine. I would honestly find the average between between the two and use those values.

Do you have massive temp swing from morning to night? Summer only car? Spring, summer, fall car? If the temperature is faily constant I would just do the above. If you drive it year round with all 4 seasons I would get a summer tune(less air) and a winter tune(more air).

[Xjas]

Thanks for the reply.

I have been reading into adjusting the temperature bias to compensate but it seem like its a bit of guessing to get it right but I will just have to persist with it.
I figured although my VE is out with the loggs of the VE AFR error from different days I can take the differenece in error from each day (logged against MAF airflow) and that will tell me how far off the temp bias is but the difference is the % change in air mass rather than temp bias error, now I need to work out how to convert that to temp bias error.
Does anyone know how the temp bias is used to calculate MAT, is it simply
ECT x Bias + IAT x (1-Bias) = MAT
or is it more that complicated than that?

[carlrx7]

i think you can log predicted MAT

[Xjas]

Yeah you can but I still need to know how its calculated, so I can figure out the required bias number once I know MAT error.

[benno25]

I had a similar issue and had some luck changing the temperature bias table. My AFR's were going lean with higher IAT's also. I slowly raised the bias table and re adjusted VE until I got more consistant AFR's with changes in IAT. It took some time though and I didn't use any calculation to determine how much to change the bias table, just kept on raising it a bit at a time until fuelling got more consistant.

Cheers
Benno

[carlrx7]

send a pm to redhardsupra or chris@hptuners

[mstrfdsstr]

this is driving me crazy to i tuned in the maf -2% @ 88 degrees in afternoon at work that nite went to leave started the car so rich my eyes were tearing up.WTF!!!!