I have practically no knock retard when running 91 octane fuel according to the Scanmaster. Sometimes I get a bit when the engine is cold but thats not an issue.

Just for giggle I put 3 gallons of the cheap stuff 87 octane in to see what would happen. The Scanmaster picked up on a lot of KR for it to be a problem especially at high load like flooring it in 5th or sixth.

The Scanmaster don't lie, so back to the expensive stuff.

I might play around with cheap gas from several different stations to see if there is a certain one that wont cause KR.

 

umm, the LT1 was designed for premium, so, yes, you will see knock with regular

 

This is true, but if it were determined that the engine would run on cheapo with NO knock retard then I would fill up with cheap stuff. The only benefit of high octane is to reduce knocking. There is no more "bang" with the higher octane. Its just nice to have a real time tool the driver if knock is present.

 

The benefit of high octane in your LT1 is higher power because there is no knock retard. Even the Owner's Manual explains it pretty clearly..... you can use low octane fuel, but you will probably lose power.

Next time you experiment, run the 1/4-mile with the knock retard and see how much you lose.

 

It confuses me when people say the LT1 was designed for premium fuel. If he goes in with Tunercats he could pull some timing in certain areas and run cheapo stuff all day. So wouldnt it be safe to say the tuning for 4th gen LT1's was set for premium fuel use?
Also my second question is I thought we had a low octane mode. If we do shouldnt the computer do whatever it is it does to go into this so called low octane mod and not show knock?
Mabey I'm just looking at all this the wrong way?

 

Agreed, I will NOT run fuel that causes KR, my post simply answers the question asked by others with absolute proof that 87 octane will cause KR, at least in my engine. The Scanmaster provides this proof. With the 91 octane I get zero KR in the quarter mile.

I am just experimenting with the octanes cause it comes to no surprise to anyone that gas costs are out of control. If I can find a lower octane cheaper gas that does not cause KR then it should perform the same as 91 octane higher cost premium gas.

If there is a way to determine this then the Scanmaster is the way. As far as a low octane mode, I think the function of reducing the timing is the "low octane mode".

 

The compression of the engine also comes into play. You can't detune compression. You can run regular in mini vans and other vehicles because they have 8-9:1 compression ratio. LT1s have 10.5:1 ratio. It needs the higher octane because 87 will possibly detonate even if the timing is retarded.

 

Good point. Forgot about c/r.