Offshoreonly.com - Highest compression on 93 octane

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Re: Highest compression on 93 octane

I will have to look this up again but I think 93 is on its out every where.

But back to the question.... Which BTW is a loaded one. I am not sure any one can say safely what max CR on 93 is. way too many factors come into play here. Heck I had a 509 Aluminum head Blown 1000hp with 8.5:1cr and 10psi of boost running on 93 with 30 deg of timing.

Re: Highest compression on 93 octane

With my 540s, aluminum heads - I was told it was ok to run 91 octane with my 10.25 compression. I play it safe and run 93.

Re: Highest compression on 93 octane

I'm in central Oklahoma, and I haven't seen 93 here for quite some time, 91 only. I'm running an AFR headed 410 ci. carbureted SBC, 10.4:1 cr. @ 33 degrees timing. 12.2 air fuel ratio on the dyno. No issues so far with 40+ hours.
91 octane with 10 percent 110 octane gets me 93, and a little more peace of mind.

Fuel blending calculator:
http://www.ranney.com/~mjr/fuel_blend.html

Re: Highest compression on 93 octane

93 octane like hi-test, is on it's way out...
We can thank the Epa and some stuffed shirts trying to justify thier jobs, as well as the oil companies and manufacturers really not being concerned with the performance boat market. Really though, why in heck should any gasoline containing Ethanol or even worse Methanol, be introduced into a boat. A 1987 Mercruiser book that I have describes all of this. They knew 20 years ago of the effects of Ethanol in a boat, also said not to use it, and they even knew it would wreak havoc on a fiberglass tank. I guess this is because somewhere in the U.S. or even elsewhere ethanol had already caused problems.
I heard some senator had major boat problems lately, and is trying to lobby or do something to help the boaters that are suffering never before seen problems due to ethanol.
I'd try to keep the Comp ratio down to at least 9.75-1 and that's pushing it.
Maybe not if you blend some racing fuel, but a bad tank of gas will wreck (detonate) a motor that is on the edge and not having the added cussion of maybe adding 5-10 % race fuel. BBB