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      06-24-2011, 05:02 PM   #95
Kinzer S13GT
Avid enthusiast... is to put lightly!!
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Drives: Black Coupe
Join Date: Jul 2009
Location: Miami, FL

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Octane is the measurement of a fuels ability to resist burning or igniting. The higher the octane, the higher its resistance. USDM ratings for these engines are calculated using 91 octane fuel. If you are using higher than that (93 here in S.Florida), then you are giving yourself more of a cushion than they even calculated for. IE; its safer! The engine has the ability to make more power on 93 than 91 octane, as the burn is more controllable!
Using direct injection (HDI/DI) effectively increases the octane rating of the fuel supply.
It doesnt eliminate the possibility of pre/post ignition, but Its far more efficient than port fuel injection, in more ways than one! Besides... 22psi, is not being pumped at idle. Thats not even possible on a conventional turbocharger setup. You only see numbers in that level per rpm in heavy duty diesel trucks. Either way... I have seen seen vehicle running 24 psi/g on 93 octane pump gas, on lesser vehicles. There is nothing to worry about here... BMW is not giving arbitrary information here! That 22 psi could be at an average "cruising" output, or it could be a "PEAK" value! I won't know definitively for another few months!