Highest compression on 93 octane
 

Running 93 octane what is the highest compression I can run on a NA motor with aluminum heads.

Re: Highest compression on 93 octane
 

I ran 10.5:1 on 93 Octane with a solid roller and never a problem...keeping cylinder pressure under control is key.

Re: Highest compression on 93 octane
 

Currently Have 10.7:1 No Problems

Re: Highest compression on 93 octane
 

Are you guys able to readily get 93 octane at the pump? Around here in California-Nevada I haven't seen above 91 octane for several years. Not talking the occasional race pump but premium gas at the average station.

Re: Highest compression on 93 octane
 

EVERY GAS STATION ON THE ROAD IN HOUSTON HAS 93 OC
ON THE WATER IS A DIFF STORY :(

Re: Highest compression on 93 octane
 

That figures. I didn't know different regions were selling different octanes. We pay some of the highest prices here and they're aso slipping us lower octane as premium. Really sucks sometimes to live in the Republic of Kalifornia.

Re: Highest compression on 93 octane
 

93 is not a problem but sunoco ultra 94 is no where to be found

Re: Highest compression on 93 octane
 

What Ever Happened To Amaco Ultimate That Chit Was The Bomb For Pump Gas. I Remember It Had The Little Window On The Handle So You Could See That You Were Pumping Clear Gas.

Re: Highest compression on 93 octane
 

Amoco Ultimate is around. We have it in 92 Octane here and I have seen it in 93 in LOTO/Missouri.

Re: Highest compression on 93 octane
 

Damn i have only seen a few places around me with 91 oct, let alone 93 on the water. with a set of aluminum heads I have seen as much as 11 to 1 with out any problems.. dynamic comp ratio, quench/squish, head material, engine temp, combustion chamber shape, all play an important part, would i run that on the water probably not..

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