Compression ratio and fuel

arielfal

Member
Hello everyone,

I have a hemi 212 and I've measured everything and calculated a 11.4 to 1 compression ratio.

What would you guys suggest for fuel?

Thanks!
 

flattop1

Dawg 89
93 -100 octane should do it .
Methanol you advance it as it burns slower .
 

arielfal

Member
93 -100 octane should do it .
Methanol you advance it as it burns slower .
Do you think I could get away with 93? I've got everything but a stroke crank in this build. I was targeting 10.5:1 but the "drop in" wiseco piston is actually 0.020 taller than the stock setup and jumped my compression ratio up which is really annoying to me. Already have the thickest head gasket.
 

flattop1

Dawg 89
Watch the plug check , the piston with a light .
Specks on the plug indicate preigniton/detonation .
You Would need a open type plug not the 3910x it would be hard too read .
Nothing too hot to start .
How much advance you have is a factor .
Then there is always octane booster .
 

1fasttiller

Member
Keep timing on the low scale and you'll be fine with 93 octane. If you advance timing upwards of 32-38* I'd be using methanol or race gas.
 

OVALTECH1

Premium User
11.4 to 1 with an aluminum head and 34ish degrees of timing there is no reason 93 pump fuel won’t run that all day long...
 

alvin l nunley

Premium User
Remember; octane is a measure of a fuel's ability to prevent detonation, nothing more, higher octane is not hotter, it is not more powerful, it will just prevent detonation, which is caused by excessive heat and/or pressure. Heat and/or pressure, as they increase, make more horsepower, up to the point where the fuel starts detonating. When a fuel starts detonating, long before you can hear it, the horsepower starts dropping. Preignition, a situation where the fuel spontaneously ignites, before the spark plug fires, is not detonation. Preignition is often caused by too hotter of a spark plug or a deposit in the combustion chamber which is hot enough to ignite the fuel mixture.
 
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