I have a 383 that runs great on pump gas.
When I went to the track, my friend who was also racing, poured some C-12 race gas into my tank. My car did not seem to run as well as usual, especially on the bottom end.
Any thoughts?

 

octane makes the flame burn slower... less detonation with high compression.

it in turn makes an engine that isnt ment to run it slow down because it doesnt make the largest bang for the time in the cylinder... high compression high rpm and its great low compression low rpm and it will bog and burp

ZD

 

Too much octane won't do any damage except to your pocketbook.

 

What do you consider low compression?

 

Uh, octane isn't an ingredient in fuel, It's a number that represents how the fuel burned or performed in a standardized combustion test. I have an old Drag Racing magazine around here somewhere with an excellent article on performance fuels, I'll find it, scan it, and e-mail it to whomever wants to read it. (it is copyrighted, so don't post it publicly!) The higher octane fuels DO NOT burn more slowly, but they are more resistant to detonation, so you can run more advance on your timing if it helps your E.T.'s. (like maybe 38-42 degrees instead of 34-36)

 

oops

sorry for the misinformation... the octane rating shows how detonation resistant the gas is :confused:

now i got myself all confused... got to go find my book about engines

ZD

 

Big Mark,
Thanks for the offer on the magazine copy. Please forward it to
will_shepherd@hotmail.com

 

This is something that will be argued till the end of time. Me, I'm in the "more resistant to detonation camp". However, everytime I've said that, someone has said, "No, it burns slower". So, sometimes I'll say burns slower to avoid conflict. There are two ways of looking at it. If low octane fuel (less resistent to detonation) pre-detonates, the fuel is burned up and expended while the piston is still on the compression stroke. So, one could argue that it "burned quicker". The pre-detonation is caused by the heat build up during compression. Compression causes heat. So the more volatile fuel will spontaneously combust from the heat caused by compression, not from the flame created by the spark plug. The way I would explain it is that it's like burning a candle from both ends. Because you are using two flames and the same amount of fuel, the fuel will be expended faster. There's also a bunch of other crap about sound waves colliding causing the knock, and the power robbing properties of the burn taking place too eraly on the compression stroke but that's irrelivent for this discussion. However, with higher octane fuel (more resistant to pre-detonation from compression), the fuel will not pre-detonate, so the fuel will only burn once the ignition flame started by the spark plug hits it, therefore, it completes it's burn later and at the proper time, propelling the piston back down the cylinder.

As I said, two ways to look at it. More resistent to pre-detonation, or burns slower. One causes the other.

P.S. Time to go get another beer :D :cheers:


[Modified by 79MakoL82, 6:53 PM 10/30/2001]

 

It may take me a few days. I have HUNDREDS of magazines to go through. Enough to make a decent down payment on a vette. Of course, without all those tech articles, I never would've learned enough to change engines, transmissions, leaf springs, do wiring, install stereos, install a home security system, build a workbench, install kitchen cabinets, lay tile...etc. etc. etc.... :)

Well, I looked around and apparently that issue has been discarded. Sorry.

[Modified by Big Mark, 11:45 PM 10/30/2001]


[Modified by Big Mark, 9:01 PM 11/5/2001]