octane boosters

Copy and paste of the most common formulas passed around the net.
Supposed to be based on what is in the OTC bottles...

 

thanks for all the info...

 

So here's what I've been wondering... how do you know what the right octane to run in your engine is? I assume that is a pretty complicated question, but is there some kind of guideline say, based of compression ratio that you can guestimate with?

 

You should run the lowest octane possible that does not detonate/ping.
However, sometimes damaging detonation can be inaudible, so you have to read your spark plugs carefully.

Generally speaking, 8.5:1 should run on 87, 9:1 on 89, and 9.5:1 on 93.
That is my experience anyway...
However, spark plug range, timing, outside temp, and several other things can influence this. An engine with aluminum heads can generally run 1.0 point higher. LSx engines have computer control of timing, knock sensors, and aluminum heads... They run right on the edge with around 11:1 compression. Mine had the lowest available compression with 10.7 and it could ping on hot days in traffic running on 93.

 

I have been mixing AV gas in my tank for years. AV gas is 100+ octane low lead aviation fuel. It is $4/gal. at this time. It gives me a little bit of lead + octane boost. I park my car for the winter and I fill it with AV gas. It will not go bad. I have had a car stored for three or four years and it fired right up and ran great. Some airplanes sit for extended periods of time so they don't want it going bad. Our local airport is small and very handy so it isn't a problem to get it here.

 

Octane Boost

Ratio 411,

Well said!

More octane equals a slower burn rate. Running more octane than needed can carbon up a motor and actually raise the octane requirement over time. It will create it's own need.

My 351 has 8.5 to 1 compression and a lopey cam in it and is just fine with 89 octane. This is what I drag race with. The cam bleeds off enough low speed cylinder pressure, that it doesn't need 93, and it has all the spark advance in by 3000 rpm. If doing highway miles, 87 is fine, because for the most part, you are not on the throttle enough to make it detonate.

If I pull the motor, I am planning on 9.5 or 10 to 1 pistons, depending on steel vs.aluminum heads, and then it will be time for 93 octane.

 

I use nos, ( not the parts store stuff ) as a adi. (anti detonation suppressor). This was used in world war 2 piston engine air craft as a adi.A small shot goes a long way, Not to mention the extra power that comes from the extra fuel that goes with the nos. Try it i promise youll like it. Cost is approx. 4 dollars a pound.

 

another opinion..this has been discussed on the fe board and most are of the conclusion that there is no way that a 12 or 16 oz bottle of anything "off the shelf" is going to have a substantial effect on a 16 gal tank of gas. I don't think the math works out too well, considering that little bottle probably only has 2-4 ozs of any active ingrediants anyway. I just buy a bit of cam2 and throw in a few gallons when I fill up.