Octane ratings

Sorry Bill, but that's incorrect. Racing fuels only work efficiently in very high compression engines, or those that are highly boosted through turbocharging or supercharging. The extreme heat and pressure created by the high compression and/or boost cause the high octane fuel to burn faster than it would in a lower compression engine. The burn rate of a given fuel is a function of heat and pressure, it's not constant.

A clogged cat generally just causes a loss of power. I've never heard of one causing detonation and if you think about it, it seems pretty unlikely. High backpressure prevents exhaust gasses from exiting the cylinders efficiently. Exhaust gas that isn't expelled has the effect of reducing combustion temperatures, which is why engines used EGR (Exhaust Gas Recirculation) systems to reduce combustion temps (which reduces the formation of certain pollutants).

That's typical of knocking/pinging problems in general.

Definitely.

"Racing fuel is always ...." is a risky thing to say with so many kinds of racing and different racing fuels.

For example, Formula 1 cars run on plain old pump gasoline, but they rev toward 20,000rpm if not higher.

Their "rac> Just to get it straight......higher octane ratings DOES NOT mean

OTOH, Indy cars burn methanol, which naturally has a very high octane rating.

Hi,

Could you please tell me what "cat" is? Catalytic Converter? thanks so much!

yes

Not to argue the point but my impression is that methanol has a lower octane rating than does regular gas.

Nope. Both Ethanol and Methanol have much higher octane ratings than pump gasoline.

Please allow me to correct myself before I take any more hit on this. When I said "always over 100", I should have said "almost always", and I was refering to petrolium basd gas. My appologies.

On this I will agree to a point, but lower octane fuel that is put into high pressure situation of the race engine will ignite from the heat and pressure alone and not by the spark as it should. That is what I am talking about. I should have explained myself better.

On this point, I have seen it happen more than once. I have seen a clogged cat. turn an exhaust manifold cherry. The EGR is only open when there is almost no load on the engine, and is considered an inert gas, so it doesn't burn again and causes less heat. It is in a loop- back configuration and is not causing back pressure.

agreed, but this could make it worse.

;)

Sorry, I should have said almost, just as you should have. Formula 1 cars run on plain old pump gasoline but with some addatives likeToluene which makes the octane rating shoot way up.

Thanks for the correction. I think I was confused.

Impressions are nice, but facts are better. Your impression is wrong.

Matt