[Joshinator99]

Originally Posted by KingLT1

The LT4 engine is on the edge of knock even with 93 due to it's aggressive timing table. Even if ECT and MAT are within check they will still see some KR unless it's cool/cold out. The 100 octane helps prevent KR. ECU doesn't default to low timing tables if it sees some KR either. It has to see a specific amount at different loads for that to happen.

I agree if the MAT's are high then it will pull timing regardless, but that isn't what Josh or myself was talking about. GM tunes these engines to knock and rely on the knock sensors save them. They are fed a lot of timing and have the knock sensors set to be very sensitive. Yes that sounds stupid I know...not sure what the theory is behind that but that is what they have done. The LT1 does the same shit. I have seen it tuning a few different combinations myself a long with other reputable names in the business.

Bingo.

[SSUNDVL]

pump gas has a lot of variables and 93 octane at 1 station in one area and another station in another area might be drastically different.

[radz28]

Originally Posted by KingLT1

The LT4 engine is on the edge of knock even with 93 due to it's aggressive timing table. Even if ECT and MAT are within check they will still see some KR unless it's cool/cold out. The 100 octane helps prevent KR. ECU doesn't default to low timing tables if it sees some KR either. It has to see a specific amount at different loads for that to happen.

I agree if the MAT's are high then it will pull timing regardless, but that isn't what Josh or myself was talking about. GM tunes these engines to knock and rely on the knock sensors save them. They are fed a lot of timing and have the knock sensors set to be very sensitive. Yes that sounds stupid I know...not sure what the theory is behind that but that is what they have done. The LT1 does the same shit. I have seen it tuning a few different combinations myself a long with other reputable names in the business.

I think LT4s start pulling timing just before 150* at MAT. And MAT is different than IAT or IAT2. Even though I see 90* at IAT2, the MAT is extrapolating something like 150* or whatever, and I can see the ECM pull a could degrees of timing at that point, until the PCM sees coolant, ambient, and inlet temps start coming down (there are more inputs, if I recall, but you get the picture).

Wouldn't it be fair to assume a strategy to utilize 100-octane better would be to raise the High Octane table timing (at specific points) knowing MATs are going to start retarding at a particular temp, and let the MATs pull timing down to the relative level GM wanted? That's how I thought of it anyways. I've seen 21* WOT on a ZL1 with a can of Racegas concentrate blended with 91 octane and see MATs pull a couple degrees once temps are into the lower 150*s.