mike13

iTrader: (27)

How does the PCM decide which table it's using? Is it by knock? Also on hptuners is there a method or device to make sure your running the high octane tables?

Thanks this is all new to me

sroach20

iTrader: (31)

when the maf fails it goes low. in hptuners you copy the high to low.

foff667

iTrader: (2)

In most LS1 applications you can log the knock learn factor to see if you are using the high or low octane table, our help file has a nice description of how the high/low tables work.

Mike454SS

iTrader: (4)

You should only do this if you're tuning the VE tables (and thus have the MAF failed), and copy them back when you're done. If you're just copying them and leaving them, thats very irresponsible in the tune as it's not leaving the PCM any choice when something does go wrong.

mike13

iTrader: (27)

So I would only be using the low octane table if I had a failure, certain codes and knock? If you where running on the low table would the pcm automatically switch to high octane if the failure or condition changed?

backchannel

doesn't it still use knock retard to lower timing--just reverts back to high table instead of learning to stay in low table?

Mike454SS

iTrader: (4)

Knock retard pulls timing for a set time, and then gives it back, and with bad gas, that will result in knock again and again and again...with proper functioning low octane tables, when the car knocks enough, the PCM will give up and run solely off the low octane tables until you fill the tank...then it will try again...knock retard can't function until it see's knock...so it has to let it come back and knock...what would you rather have your engine do?

macca_779

Think of the initial detection of knock in the same way as STFT's. They'll fix it for the moment but wont remember for later. Then think of Adaptive Spark (The blend between high and low spark tables) as LTFT's.. That's about as simple a description as I can think of off hand.
If you don't know how fuel trims work, that description probably wont help you.