Octane ratings

Just to get it straight......higher octane ratings DOES NOT mean slower burn time, it means that the gas can withstand higher heat and pressure before an uncontroled explosion. The only to use high octane
is to help prevent pinging and detonation in high compression and forced induction engines. Racing fuel is always above 100 octane, and some is as high as 140. This would not work at 8000 rpm if it was a slow burn time. For the problem with the Elantra, check the cat. it may be cloging. If it is, the back pressure would cause more heat and detonation. The problem would be amplified a high rpm or under a heavy load, like going up a hill. Higher octane may help a little, but I don't think it will solve the problem. Get it checked out soon. Detonation and pinging will ruin your engine. Bill
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billyboy24d wrote:

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.
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When I said "always over 100", I should have said "almost always", and I was refering to petrolium basd gas. My appologies.

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.

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.

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"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 "racing fuel" is the same stuff you can get at a gas station although someone is paying a LOT more attention to the quality of every liter used in an F1 car. They are not allowed to use octane boosters or additives.

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PMDR wrote:

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

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Brian Nystrom wrote:

octane rating than does regular gas.
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James wrote:

Nope. Both Ethanol and Methanol have much higher octane ratings than pump gasoline.
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http://www.leeric.lsu.edu/bgbb/7/ecep/auto/m/m.htm Higher octane, less power per gallon
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Brian Nystrom wrote:

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James wrote:

Impressions are nice, but facts are better. Your impression is wrong.
Matt
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cars run on plain old pump gasoline but with some addatives likeToluene which makes the octane rating shoot way up.
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Hi,
Could you please tell me what "cat" is? Catalytic Converter? thanks so much!
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yes
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