More on octane

[reddelsol]

I didn't buy the mag (cause there wasn't anything else in there I was interested in) but Hotrod ran a short article on octane.

main points that I came away with.

Race gas (and/or as a mixture base) is your best bet for preventing detonation AND enhancing performance.

While they said octane boosters do work, some additives slow the burn rate of the gas. This will prevent detonation but decrease performance. (we don't want that) But, if you don't have alternatives it's likely you would be best served getting rid of knock while sacrificing some performance. Unfortunately, I don't recall what if any gas additives specifically were mentioned. No mention of stuff like Toluene.

Also, in tests on their engines, they found that increased octane helped performance to a certain point with timing increase, but the engines they used all seemed to have optimum points of timing, and bumping up octane levels and timing after that point either produced no more horsepower or even decreased horsepower. Which means to me, no sense over octaning your engine as you might just be wasting money or even lowering your power output.

That's all I remember, (though it was a short article anyway)

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"There's nothing wrong with the car except that it's on fire."

[dbman96]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by reddelsol:

While they said octane boosters do work, some additives slow the burn rate of the gas.
<HR></BLOCKQUOTE>

I was under the impression that Octane is nothing BUT a measure of how slow the burn rate of the gas is. If not I need to have a chat with a couple of my old professors.




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[bobbrown]

I suppose you can think of octane in that respect. That may be closer to the thoretical definition.

Higher octane fuels tend to burn a little longer and require more compression for complete combustion. This is why we advance the spark timing when we are using a higher octane fuel - it allows more time for the fuel to burn. A longer combustion means the burn is taking place over more of the crank revolution, in turn giving more power. This can lead to slightly increased cylinder temperatures.

Increases in the cylinder temperature are only a problem if it leads to detonation. When we retard the spark, we allow for a shorter duration for the fuel to burn. It also allows for more time for the air/fuel mixture to quench the piston domes prior to ignition, further lowering cylinder temps. The shorter burn cycle that results from retarding the spark lowers the cylinder temp, but at the loss of some power.

The best way to think of octane is the gasoline's ability to resist knock or pre-detonation. This is the most practical paradigm when applied to cars. http://www.chevron.com/prodserv/fuel...5Foctane.shtml

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[bobbrown]

I have written a couple of threads on race gas. I have been using it in my car for the last 3 months. Since I don't drive my car that much, I can handle the pricetag of $4/gal. With the race gas I run 18-20 degrees timing BTC with no boost retard. I have no problems with detonation and I get substantially more power. On the dyno I get about 217 at the wheels and that's with only 6psi no other mods except the basic bolt-ons. So I can personally attest to the huge benefits of running race gas. Not only do I have a lot more power, I get better mileage, my engine feels smoother, and my vacuum to boost transition is like glass. I live in the South Bay in NorCal and there's only one 76 station that sells it at the pump. I don't no where else to get it. But if you can find it, it's well worth paying the extra cash as treat for yourself every once and a while. To take full advantage of the 100 octane race gas, advance the shit out of your timing and pull back on the boost retard(if applicable).

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