killerv6

can anybody tell me when they when they put that tune in my car what changes it makes to the computer for the engine

NineVettes

If you do a search on this forum, you will see a very definitive discussion about 100 octane tune from GM. Since I live in north Fl, I was thinking of getting this tune for my '19 Z. Idea was to mitigate effects on pulling timing during the warmer months. Getting 93 octane here is no problem, neither is access to 100 octane. After reading the discussion, I think that will keep the stock tune, which evidently will react with some less timing pull using fuel up to 95 octane or so. Of course, that is if I understood the discussion correctly! My concerns with getting the 100 Octane tune is what would happen if you got a bad batch of lower octane fuel - the knock may be severe enough to cause damage.

Higgs Boson

it only changes the amount of spark lead reduced preemptively from intake air temps. this table pulls spark whether there is actual detonation or not, it is proactive not reactive.

the 100 octane tune effectively runs more spark lead at higher intake temps and that is what necessitates the use of 100 octane. the rest of the tune is the same.

NineVettes

So running a bit higher octane will do nothing to mitigate the stock preemptive spark lead from temps? If so, then running higher than 93 on stock tune is worthless?

Mikec7z

yes and no... if higher than 93 octane prevents actual knock, when the 93 alone would not have prevented actual knock, then the higher octane had a purpose... as the engine drastically pulls timing when it detects actual knock.

Higgs is correct tho, it does not change the actual timing so to speak, it stays equal with the stock tune...

the difference is that hotter iat's don't create preventative timing pulls with the 100 octane tune vs the regular tune, which does do the preventative pulls on a more aggressive basis based on the iat's rising.

If you are going to run 100 octane, i say get the tune.

If you are going to run in cool weather and run 93 and dont heat your car up a ton, i also say get the tune... but that is just my 2 cents.

Pacembellum