93 or 100 octane

[lexuspilot]

You got it....I didn't miss anything. If the maximum power you can get from similar fuel is X. Then with contaminated fuel you only produce, let's say .98x. If you get uncontaminated fuel and produce the maximum power of x then you would be producing MORE power. Not more power than that "maximum" but more than before. Plus, I never said contaminated..I said it may not have actually been "91". In this case the "91" not having the octane for the engine to "tune" to the power.

This is it in a nutshell(can't help but to think of Austin Powers), you may have realized your engines true performance on the 100 octane fuel because the previous fuel did not allow your car to extract the full amount of energy contained in the fuel.


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

[steven choi]

Thanks a bunch Larez2.
Finally someone really understood what my question was..

Thanks.

[MNBoxster]

Originally Posted by lexuspilot

...

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

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