93 or 100 octane

[MNBoxster]

Originally Posted by lexuspilot

If your engine was retarding it's timing because of insufficient octane(knocking), then adding a higher octane would increase power.

The question might be "Where you really buying the 91 octane you thought you were buying?"

Sorry, but using the butt dyno means using butt logic not labratory logic. The very long post above lays the ground work to assume that you have been buying crappy 91 only to then try excellent 100. My money would say there is a power difference in that case.

Hi,

Not to Flame you, but you seem to have totally missed the point, which is: There is no more power in Gasoline of a higher octane, and that switching to a higher octane will not give your engine more power.

The energy contained in all gasoline is basically fixed. I say basically because there are some Octane Boosters, such as Methanol, which actually contain less energy than an equal volume of lower Octane Gasoline, but they have a higher Octane Rating. So, the case can be made that there is more power (energy) in Regular Gas (87 Octane) than there is in some higher Octane Gasolines, but never vice-versa.

Your arguement that switching from contaminated gasoline to gas which is not contaminated will give your engine more power is pure Pretzel Logic or, as in your words, "Butt Logic". Your statement forces me to believe that you weren't actually serious, but only stated it Tongue in Cheek.

Obviously, if you are buying contaminated 91 Octane Gas, which causes your Engine Management to retard the timing, the car will underperform. But, that is not even relevant to the discussion. What if you had faulty Ignition Wires? Do new Ignition wires contain more Power? That's essentially what you're saying.

Happy Motoring!...Jim'99

[larez2]

I don't think lexuspilot missed your point - he never said there was any more power in the higher octane gasoline. I thouhgt his points were totally relevent - most gas station in CA only offer up to 91 octane gas. If you use gas with a lower octane than recommended - 91 in our case, where 93 is recommended and your car is not performing optimally on the 91 octane, then changing to 93 octane from 91 octane will make a difference relative to what is was before - the difference manifests itself with the feeling of restored/more power. And, I do not mean it magically makes engine higher compression. True, replacing faulty ignition wires will not make your engine "more powerful", but what it will do is restore power and smoothness relative to what is was before (with faulty ignition wires). In either case you feel a difference.

The answer to the original question from Steven Choi is, 93 or 100 octane makes no difference because our cars are only rated for use with 93 octane. Also, mixing them doesn't help or work/not recommended. Most gas stations in California only offer up to 91 octane - the way to increase the octane to the recommened 93 is with octane boosters or with Toluene.

Larez2

[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