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YOUR RESEARCHOctane
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Recommend number is a ron number
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Suggestion
However the car has knocksensors that pull timing so that there will be no engine damage from running 91.
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Suggestion · Original poster
I'm under the belief that although I can run 93 octane, under race conditions and particularly on hot days, 100 octane would be the choice.
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Suggestion
I wouldn't mind picking up some additive if it would help my car run better.
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Suggestion
Use only an octane high enough that will allow you to run maximum spark advance with no ill effects.
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Suggestion
In a high compression engine that most likely doesnt have a knock sensor it would be safer to use higher octane gas, specially under racing conditions on a hot day, you might produce more power but more importantly you will prevent detonation..
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I have race prepped 3.8L 964 engine in my 92 964 with 280 RWHP.
I'm under the belief that although I can run 93 octane, under race conditions and particularly on hot days, 100 octane would be the choice.
Does this sound accurate? I always thought the octane an engine ran was a function of timing/ignition and increasing the octane would have no positive affect. This was the first time I heard it may make the engine run more efficiently, hence cooler.
Is this plausible? Am I generating more HP with 100 octane, or would I need to "chip it" to yeild a HP gain? If chipping it would help, who would make the "chip of choice"?
It depends on a number of factors but primarily compression ratio. If you have a particularly high compression, the engine will need high octane gas to make max power. Using lower octane gas will require some timing to be pulled to prevent detonation. For lower compression engines, they can use optimum timing on lower octane gas with no detonation so there is no performance gain from going to higher octane.
Ian
If your timing is not being retarded with 93 octane fuel, then using a higher octane will give you no performance benefit. However, the higher octane will provide you with more protection from knock on hot days. More of an insurance than anything else.
In a high compression engine that most likely doesnt have a knock sensor it would be safer to use higher octane gas, specially under racing conditions on a hot day, you might produce more power but more importantly you will prevent detonation..
Use only an octane high enough that will allow you to run maximum spark advance with no ill effects. Any higher is not only a waste of $$$ but foolish in that you are consuming a slower burning fuel than needed and the results will be LESS potential power.
Should those of us living in California, where 91 is the most you can get from most stations, be adding an octane booter? I'm speaking 996 (this IS the 996 board, after all), I think I've heard that the engine was designed for 95 octane, right?
I've been sticking with Chevron Supreme 91, because I've fallen for the marketing hype on Techron and the quality of Chevron gas. I wouldn't mind picking up some additive if it would help my car run better.
I'm not sure, but I think this may be apples and oranges. I might be wrong, but I think the manual gives you a RON number for octane, whereas what you see on the pump is an average of RON and MON. Remember that octane isn't a substance, it's a property. The octane rating shown on the pump here is usually 5 or so points lower than in the rest of the world, so 95 octane in Germany is equivalent to ordinary 91 octane premium fuel here.
With my 997S I have found the engine to perform with less noice when I have ST104 (octane additive) added to the tank. 91 is typical California but Porsche suggests 93 as the minimum. With the VarioValve engines the octane is less an issue, but you do trade away performance/HP/mileage.
Again, read the manual. Porsche's recommended number is a RON number. Pump octane is an average between two scales, RON and MON. Your 91 pump is the same as the 95 Porsche recommends.
You are right the averaged (as california rates it) is 93. However the car has knocksensors that pull timing so that there will be no engine damage from running 91.
You do not
need
to use a booster. But you could use a booster.
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