[LT1Zob]

If any of you were 5th gen guys and gals, you'd probably remember the old days of fuse 5 and 20 pull overnight to reset the fuel tables.

I recently bought a 23 LT1 with 10k miles. I always run premium in my fun cars. I'm fairly certain the previous owner put in 93, based on how he treated the car, but have no way of knowing for sure. And God knows what the dealer put in it.

Any way to "reset" the LT1 and know i'm putting in premium from here on out?

[arpad_m]

Maybe the pro tuners here will know more, but I don't think you can reset fuel table references to force the ECM into the high octane table (happy to be corrected, though). The good news is that the ECM will learn this (from the knock sensors) and move over to the high octane table automatically, the slightly bad news is it may take some time/miles.

[LT1Zob]

Thank you for your response. I’m hoping so.

[Joshinator99]

Arpad is right. Just drive the car with the 93 octane fuel and the engine will slowly add the timing back in (if someone did indeed run 87). Within a full tank of gas you’ll be up to speed I’d say.

[Ray3768]

Having recently come over from a 5th gen as well, I had the same question. I kinda assumed that the updated PCM would have addressed this and it was no longer an issue. So let me add a second question. In my case, the car had 1 mile on it when I test drove it. The fuel gauge was pretty much on E and and low fuel light was on. The salesman had me immediately drive to a gas station and fill it up with 93 octane (using the dealers credit card of course). So my question is what octane fuel does the factory put into a new Camaro SS?


-Ray

[Joshinator99]

Originally Posted by Ray3768

Having recently come over from a 5th gen as well, I had the same question. I kinda assumed that the updated PCM would have addressed this and it was no longer an issue. So let me add a second question. In my case, the car had 1 mile on it when I test drove it. The fuel gauge was pretty much on E and and low fuel light was on. The salesman had me immediately drive to a gas station and fill it up with 93 octane (using the dealers credit card of course). So my question is what octane fuel does the factory put into a new Camaro SS?


-Ray

I don’t know what they put in for fuel from GM, but you will definitely leave WOT power on the table with anything less than 93. That said, during their SAE power testing they undoubtedly ran at least 93 octane. The engine is very high compression and will experience knock retard on low quality gas…heck you can even see some knock retard on 93 in high heat high load situations.

[Ray3768]

Well I wouldn't exactly call 11.5:1 a very high compression ratio. In fact it is exactly the same spec as the gen 1 LT-1 (boy, those were octane limited). The gen 2 LT1 had 10.4:1 static compression ratio and did well with it's port fuel injection (mine did great on 93). Octane sensitivity tends to be due to combustion chamber heat transfer rate and the actual dynamic compression ratio as dictated by the camshaft. Our gen V engines have the added benefit of GDI which allows multiple pulses of fuel throughout the cycle to aid in cooling the combustion chamber (a game changer), which also reduces octane sensitivity. This is a wonderful brave new world in which we live in. Some Mazda engines have a static compression ratio of 15:1. Crazy stuff. My point is that octane sensitivity is not dictated by the static compression ratio, but more so by the dynamic compression ratio or actual cylinder pressure AND the heat transfer rate to the coolant/oil/atmosphere. Remember, thermodynamics is our friend.

-Ray

[LT1Zob]

This one I know from the Corvette forums. I’m in a state that offers 93. There are states like CA and CO that’s don’t offer 93, only 91. So my understanding from vette engineers is that the ecu is optimized to 91 octane. That’s my understanding on my LT4

[Joshinator99]

Originally Posted by Ray3768

Well I wouldn't exactly call 11.5:1 a very high compression ratio. In fact it is exactly the same spec as the gen 1 LT-1 (boy, those were octane limited). The gen 2 LT1 had 10.4:1 static compression ratio and did well with it's port fuel injection (mine did great on 93). Octane sensitivity tends to be due to combustion chamber heat transfer rate and the actual dynamic compression ratio as dictated by the camshaft. Our gen V engines have the added benefit of GDI which allows multiple pulses of fuel throughout the cycle to aid in cooling the combustion chamber (a game changer), which also reduces octane sensitivity. This is a wonderful brave new world in which we live in. Some Mazda engines have a static compression ratio of 15:1. Crazy stuff. My point is that octane sensitivity is not dictated by the static compression ratio, but more so by the dynamic compression ratio or actual cylinder pressure AND the heat transfer rate to the coolant/oil/atmosphere. Remember, thermodynamics is our friend.

-Ray

It’s a major factor. The Gen2 LT1 had tricks like reverse flow cooling to help deal with the high compression, FYI. I know because I had a new ‘97 WS6 that I promptly turned into a 383 stroker with nitrous. But compare that to many other engines and 11.5 is still not inconsequential. And you learn a bit on the road to 1059 WHP…

Originally Posted by LT1Zob

This one I know from the Corvette forums. I’m in a state that offers 93. There are states like CA and CO that’s don’t offer 93, only 91. So my understanding from vette engineers is that the ecu is optimized to 91 octane. That’s my understanding on my LT4

False, the LT4 is octane limited even on 93.

[LT1Zob]

Originally Posted by Joshinator99

False, the LT4 is octane limited even on 93.

Thanks. I’m going off of memory on a forum from a few years ago. If you know for a fact, then 93 is the answer.

[Joshinator99]

Originally Posted by LT1Zob

Thanks. I’m going off of memory on a forum from a few years ago. If you know for a fact, then 93 is the answer.

Yeah so just to clarify, the car can definitely run fine on 91, but you simply won’t get max power…especially in high heat or heavy load situations. Check out some of KingLT1’s posts in this forum…he tunes them regularly and sees it in the data logs first hand. GM made the car usable on 91 of course….but most of us on this board are power junkies haha.