Thread: Octane Booster?
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      09-10-2008, 05:12 PM   #13
GT3 Tim
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Drives: 2014 MB E63S
Join Date: Feb 2008
Location: Sacramento, CA

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Originally Posted by BMW-M-Mexico View Post
Hmmm! Funny. Where is that dyno? Somehow I doubt that is true. What may happen however is the anti-knock sensor "senses" knock and reduces timing etc... automatically (We now the M3 engine has this sensor). And, for instance, when using lower octane fuel than 93 (that is where the engine is tuned stock), the hp produced will be somewhat less than 414bhp DIN. When the proper fuel is again administered, the engine will not sense knock and will, in time (by no means in a few minutes), return to its regular tune. This may explain why you feel a power increase with improved gas (because somehow shitty gas ended up you your engine) but when using say 104 octane, there is no way the engine can "retune" itself to produce more power than where it is optimized from stock which is 93 octane.
Check out PencilGeeks dyno results with 100 octane and 91 octane. He got a decent increase in power.

I don't totally agree with the last part of your post about the car being tuned for 93 and not producing more power after that. Fact is, the jury is still out on that. PencilGeek proved that octane ABOVE 91 is beneficial. The question is how much above 91....Even though he used 100 octane, it is possible that you would realize no gain in hp above 93....but it is impossible to tell at this point as we only have data for 91 and 100. You may be right in that the car is capable of advancing the timing up to what would be required for 93 octane. But without data for octane in incriments of "1" or so, we cannot be quite sure. Personally, I doubt anything much higher than 93 would be of benefit (actually, the higher the octane, the LOWER the specific energy). So anything much higher than the car can accomodate (timing) could actually result in less power than the theoretical max (93 or whatever it may be).

Anybody want to mix some fuel and toluene (accurately) to achieve octane incriments of "1", drain their tank each time, and dyno test each batch to see what's the best octane level to use? lol

93 may be the max.....but we cannot claim that it is at this point in time, unless there is data to support it. Is there data to support it that I did not see?

edit: Side point....even though we may get a 10hp increase, I doubt you are going to feel it.
Tim <--- apparently likes "3" cars
2014 E63S -- The Rocket
2014 F30 328i -- Kids car
2008 E90 M3 -- Sold
2004 GT3 -- Sold
1997 M3/4 -- Sold
1995 M3 -- Sold