jdm767

I had a 383 stroker built on an LS1 block. All forged rotating assembly, Trick Flow 220 heads (57cc chamber?), aggressive cam etc etc etc...

The initial tuner did not put a rev limit into the programming. In fact, he wasn't sure what it should be.

So, in consideration of the higher velocity of the pistons at higher RPM, does anyone know what would be an appropriate rev limit?

Second, the builder estimated the compression to be about 11.5:1 and that he could tune it to burn 93 pump gas. Well, it actually is just north of 12:1 and does not like 93 octane! It detonates under load. I'm thinking (a dangerous pass time - I know) that I should mix 93 and race fuel to get the octane up. Your thoughts please?

Thanks in advance!

SVT_Z06

With that kind of compression you can get some great results with E85.

tblu92

The rev limit and the spark timing related to pinging have nothing in common
Typically you want to set the rev limiter or shift point on an automatic car to be "where in the RPM range your cam quits making HP "---Depending on your cam the higher the duration the higher the shift point----Typically a stock cam signs off about 6000 RPM's
A can in the mid 220's duration about 6400 RPM --a cam in the mid 230's about 6500-6700---and a cam larger than 230 can have a RPM limit up to 7000
There is no advantage to run your engine above the RPM range where the cam starts making less than peak HP--Ideally you would want to shift at PEAK HP and have the RPM's drop down only to PEAK TQ when shifting----This is called the "power band"
Now as far as timing and pinging goes- this has nothing to do with RPM shift points or max rev's---- You ideally want to get as much timing as you can get into your engine without any detonation or KR---Based also on the oct level of your fuel and or the static compression of your engine------If you have high compression and pump gas---sure you may not get max HP because of having to limit timing --- but that is your choice on wether or not you want to run race fuel all the time--But the MAX HP RPM levels will not change based on fuel or timing----It is based on where your cam begins to start making less peak HP---

jdm767

Thank you for your response!

I am aware that the rev limit and the detonation are unrelated - I was just asking multiple questions.

We're going to put the car on the dyno next week and will use a wide band to tune it.

I like the idea of E85, but it's hard to find in Connecticut. Not impossible, just difficult.

Race fuel may be the way to go, or even a watered down race fuel (50/50 blend).

Thanks again for your insight! It is very helpful.