I was wondering if I could get a general rule of thumb (so to speak) of fuel octane levels to sustain diffrent compression ratios. Starting at about 8:1 thru 16:1.

I know that there are many other thing to take into consideration. Like Altitude, Barometric pressure and a few other things. What I want is just a rule of thumb ( If there is such a thing)?

What and how much will it affect Octane level?

I have read the link from the Home page on fuel additives. Very interesting, But not what I was looking for.

I have heard that LPG (Liquid Propane Gas) is 105 Octane. Is this true?
If so how much compression could you put to it before detonation begins to start?

And last but not lest Has enyone taken a Ford 460 and raised the compression to the Max for LPG to drive as a work truck. Then switched it to sustainable Race fuel for that compession ratio for street RODDIN every now and then. Details Please.

I know that there is alot to cover here. Any information would Gratefully be appreciative.

Thank In Advance.

 

S-A Designs puts out a book called "SUPER POWER, a do it yourself guide to Turbocharging, Supercharging, Fuel-Injection, and Nitrous Oxide". This book is extremely dated. It refers to a 77 chevy as a "late model pickup", and fuel injection talks about mechanical fuel injection. However the rules of physics and chemistry haven't changed since then. It give the 105 octane/propane reference under turbocharging, as a way to cure detonation.

Rule of thumb I've always used for street use is 9.5 to 1 max compression for use with 92 octane fuels. However it's important to realize this is static compression. The actual compression while engine is running is referred to as Dynamic compression and is a whole nother animal. For instance a large lumpy cam will bleed off the compression at low rpms. A tunnel ram can increase it by packing a little extra air in if properly tuned and setup at an appropriate rpm. Turbos or superchargers will radically raise dynamic compression.

I realize that don't help much but it's hard to be specific without details in the first place. If it helps I asked an accomplished local racer once about the propane deal. He thought I could run as much as 12 to 1 compression with a cam designed for streetable rpms(RV or one of comp cams 4x4 line).

If you want a look at that book try checking with summit or one of the online book dealers. It's so old though it may have been updated/replaced.