Degree Key

[superbanshee03]

I was wondering what a degree key has to do with running race fuel?

For instance, I have a 3deg key and my compression is 155psi, I just rebuilt mine and had it ported and I am planning on not running RF but kinda confused on what the advanced timing effects. I have herd that running RF is determined by your comp. and timing but dont know about the timming thing, could someone please help me on this!!

[bigboybanshee]

You will be fine running 93 octane with your specs....You would need to run a race gas mix (race gas/pump gas) if your timing was at +7 though. I know the reasoning behind all of it but would be horrible at trying to explain it. Someone else could probably explain this for you a lot better than I could....

[boonman]

The reason you would want/need to run race fuel at any time relies on compression, squish, and timing. In the most basic of terms. What is needed here is resistance to detonation, or pre-ignition. Two different things, but closely related. Now, as the piston is travelling up, it begins to compress the air/fuel mixture. Now, with a low octane mixture, and high compression, what would happen would be the heat of the compression stroke alone is enough to ignite the fuel. So, adding more octane to the fuel's numbers, would increase it's resistance to this. And you would not explode the mixture prematurely. Adding timing advance to this equation, can also lead to a case of the pinging engine. (a "ping" is the noise you would listen for to try to determine, among other things, like a plug check, if you are having a problem with detonation). The increased timing can give you a pre-ignition problem if you aren't running enough octane. It ignites before Top Dead Center and goves you a sonic wave that the engine doesn't like. You will lose power, and cause damage to the engine. So, to much advance, and to much compression can lead to detonation if you aren't running enough compression. You should be fine with your setup on some good 93 octane fuel.

[bigboybanshee]

The reason you would want/need to run race fuel at any time relies on compression, squish, and timing.  In the most basic of terms.  What is needed here is resistance to detonation, or pre-ignition.  Two different things, but closely related.  Now, as the piston is travelling up, it begins to compress the air/fuel mixture.  Now, with a low octane mixture, and high compression, what would happen would be the heat of the compression stroke alone is enough to ignite the fuel.  So, adding more octane to the fuel's numbers, would increase it's resistance to this.  And you would not explode the mixture prematurely.  Adding timing advance to this equation, can also lead to a case of the pinging engine.  (a "ping" is the noise you would listen for to try to determine, among other things, like a plug check, if you are having a problem with detonation).  The increased timing can give you a pre-ignition problem if you aren't running enough octane.  It ignites before Top Dead Center and goves you a sonic wave that the engine doesn't like.  You will lose power, and cause damage to the engine.  So, to much advance, and to much compression can lead to detonation if you aren't running enough compression.  You should be fine with your setup on some good 93 octane fuel.

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[superbanshee03]

Thanks, Boonman

[canyncarvr]

Not specifically related...but one myth about 'race gas' is that a higher octane fuel makes more power than gasoline from the pump.

 

Not necessarily.

 

A higher octane fuel does not make more power than a lower octane fuel, other circumstances being equal (age of the two, moisture content and such). The higher the octane, the more resistant to the sorts of things boonman already said.

 

If you have an engine that does not require a high(er) octane fuel you are wasting your money using a higher octane fuel.

 

Where a higher octane fuel is useful is when combustion pressures (part of which are determined by static compression ratio) generated require such a fuel to prevent pre-ignition, detonation and other such explosive actions.

 

The 'exploding' part isn't good. The compressed fuel charge is supposed to burn...not explode. And it's supposed to burn from a single (hopefully a planned/timed) ignition source.

 

Another by the way...the distillation curve of a particular fuel is more important than the octane number (research or otherwise). The following are the specs of (for example) Trick 114 ...a 'race' fuel:

 

Typical Properties

 

Research Octane (R.O.N.) 114

Motor Octane (M.O.N.) 106

Anti-Knock Index (R+M/2) 110

Reid Vapor Pressure 6.9

Distillation Curve (

Edited February 15, 2005 by canyncarvr