As the weather gets cooler my truck seems to get into the Knock Retard more often. Is it possible that with the cooler weather my AFR changes enough to affect this. Please advise.

Thanks

 

Are you using the MAF?

 

you'd think with the colder denser air the pcm would command more fuel....which brings us back to the Dr's ?...MAF? Definitely need a MAF to "see" the cold/dense air.

 

This was something I asked about a while back when the 2 bar tuning programs first started appearing. Since you don't use the MAF with them I was wondering if the AFR was corrected for differening IAT's. The answer was yes the computer does compensate for IAT's when running in SD mode.

If you've exceeded the limits of the MAF and have tuned the PE tables to compensate then the AFR will be leaner when the temperature goes lower than it was when you tuned.

 

If you are running OL/SD, EFILive custom cals have an Open Loop VE Multiplier table for IAT(A0014) to compensate for differences between actual IAT and IATs when the tuning was done. You can increase the multiplier for any IAT at which you are going lean.

 

I am still using MAF. I plan to get a wideband to see if Im running lean. My IAT sensor has been relocated to the elbow before the intake. The maf is way upstream well before the blower after the filter.

 

I would think that the MAF would take care of the AFR. In that case there should be less knock with cooler charge temps. Have you modified any of the spark tables? I'm guessing that burst knock retard may be more important with denser air. Then again I only heard about burst knock 45 minutes ago.

 

Most of the OEM computers add timing when the air temps drop. If you log timing you'd likely see that's what is going on. They even have modiifier tables to max allowed based on air temps. This can be eliminated or reduced in the tune.

Jody

 

with the colder denser air, your effective compression ratio also increases, which will cause the knock if you are not running high enough octane for the tune you have going.

 

It looks like I have to make a MAF adjustment perhaps? Im currently running sunoco 94 but it contains ethanol wihch is not good. Also the switch to winter gas also is pointing towards a tuning adjstment.

Please advise.