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Originally Posted by lexuspilot
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MNBoxster I will turn to you for the relevant question for your noodle. What is the tolerance on octane ratings? I would guess less than 2?
It is like drinking florida beer..sep different.
Cheers
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Hi,
OK, now that you say it another way, I guess we're not in such disagreement afterall.
So far as tolerance on Octane Ratings, I presume you mean the ECU's (or DME's in Porsche parlence) ability to adjust to differing Octane Rated Gas.
If so, there isn't truly one answer. This is because the Combustion Threshold (when Knock occurs) isn't truly static. It is dependent on several factors such as Ambient Temperature, Barometric Pressure and Humidity, cooling system efficiency and so on. Also, if you think about it, an engine knocks usually only under Load or at high RPMs, so you may be fine on a trip to the local convenience store, but climbing a hill or shooting down a Freeway ramp, or on a very hot day, knock may appear.
And, not all gasolines of a certain Octane Rating are the same. This is because any number of Octane Boosters may be mixed with it (such as Toluene, MBTE, or Methanol, etc.). Because of all these things, I suspect most ECU's are capable of compensating for an Octane discrepency of say ± 2-3 points. Hope this helps...
Happy Motoring!...Jim'99