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      01-19-2012, 02:14 AM   #4

Drives: X1, 335i
Join Date: Sep 2006
Location: SF Bay, CA

iTrader: (0)

Originally Posted by DylanMckay View Post
With how long this car has been out and how many tuners have worked extensively with this car, I am surprised to see that nobody has seemed to test what the "ideal" octane is for our cars in a somewhat controlled fashion. I know I have read speculation that our cars are capable of advancing timing to the point where 95-96 octane is needed but is there any evidence of some type of data log where the timing advance levels off? Would be nice to know.

I started using torco because I was sick of 91 octane and not making the full power this car is capable of. i am willing to change my spark plugs every 10k since they get orange deposits if it means I get the full 414 hp this engine is meant to produce. I am just surprised there is no data where the timing curve maxes out and approximatly what octane is needed to run that timing advance consistently given controlled conditions.

My best guess from random searches is 96 octane is the number where anymore does not seem to make a big difference.

I know from my "butt" dyno, going from 91 to 99 octane (which is what it is with torco), the power is unreal and unbelievably stronger, so clearly timing advances well past what 91 is able to deliver.

Any thoughts?
On 91oct (and even 93oct), the DME is rarely able to achieve the desired ignition advance set point due to knock activity. Which is why adding race gas or meth picks up the power it does. When you run it, you feel the advertised power that BMW claims. I just wish they would admit to it not being able to achieve that with US pump fuels. Same goes for the newer Porsche turbos but that's another story.

But even the timing achieved when running race gas isn't necessarily "ideal". There is still room for 2-3 deg more timing between 6000-7500rpm if the DME would allow it. This alone is worth 10-15whp. There is also some gains to be had in the 4000-5000rpm range. But the timing maps were calibrated to run on pump gas so there isn't much reason for BMW to implement these higher advance targets.

Hope that helps..