[Simple5]

As it stands my 550i is my weekend car. I drive it about 3-4 days out of the week. I slapped on the N63 Stage 1 and being in California, we have that crappy 91 octane. I drive it pretty 'spirited' when I do and I only fill up the car about once every 2 weeks due to it not being a daily.

Question: I have the idea of getting a few (5) Gallon gas cans and filling them up at a gas station where they sell 100 octane and doing a (7.5) Gallon 100 octane to (10.5) Gallon 91 octane mix. If I stick to the 7.5 gallon to 10.5 gallon formula then I will only be filling up those gas cans once a month, which isn't too bad...

Will I see any significant improvement on the n63 platform doing this with the BMS Stage 1?

[FenixMike]

Yes and no, the only real way you can tell (besides seat of the pants feel) is to watch the Knock retard from a scanner to see how much timing the vehicle is pulling. Most piggy backs add 3 lbs of boost, which in warm weather is enough to cause mild knock on 91 octane with our cars (im in AZ with a 550 and AJ worked mine on the dyno to make sure it was safe and how much boost to add) but I pull a bit of boost in the summer just because of crappy gas combined with extreme heat, or when available, mix a few gallons of E85 in the tank (30% E85).
I felt a decent difference after a while of driving (1/2 tank or so) and the car was able to feed back in some timing, and at that point you could even add a bit of boost since youre running the higher octane to keep it safe, but as stated, you really want to watch it on a scanner, or have someone really listen to hear if there is audible knock or not. The stations with E85 arent close to my house and im not wasting the money for 100 in the tank (although the reduced fuel economy of E85 sucks, its still only $2.20 a gallon), but from a safety aspect, especially if you arent car saavy and dont understand knock, it isnt a bad idea.

At least either way it will be cheap insurance on the warmer days if youre beating on it in the sun as it likely wont knock with the few gallons of race fuel in it.

[badblack550xi]

As far as I know E85 rusts spark plugs so I wont run it. Altho we have 93 here I always have 100 octane mixed in this way car does not pull timing on stage 2 3.0 psi agressive setting. And at any given time can crank it up to 3.5. What is your stock psi on 91 stage 1 ? 2.25 ?

[550Reasons]

I've been wanting to try out a smalll mix of E85 with 93

[FenixMike]

Originally Posted by badblack550xi

As far as I know E85 rusts spark plugs so I wont run it. Altho we have 93 here I always have 100 octane mixed in this way car does not pull timing on stage 2 3.0 psi agressive setting. And at any given time can crank it up to 3.5. What is your stock psi on 91 stage 1 ? 2.25 ?

E85 doesnt rust spark plugs, destroy gas tanks, or other fuel system components. All urban legends by those too scared to run it, or against it. If you're dumping raw E85 into your cylinders and letting it sit there for 6 weeks with the ability for oxygen to get in, you might have a problem, but at that point I'm sure rusted spark plugs would be the least of your worries. Alcohol cleans engine components, and unfortunately with direct injection you don't see near the benefits that standard port fuel injection sees which is the cleaning of the valves and intake ports... I loved taking my Cobra apart and seeing everything be nice and clean with no disgusting build up (which BMW has a HUGE problem with now on the direct injection cars and I'm sure other manufacturers as well).

[FenixMike]

Originally Posted by 550Reasons

I've been wanting to try out a smalll mix of E85 with 93

no reason not to, just don't exceed your vehicles ability to correct with fuel trims, which on a properly running vehicle is about 30-35%. Beyond that you will likely get a check engine light, and I also don't know anyone who has tested the limits of the 550i fuel system to see at which point its out of fuel, or the duty cycle of the injectors. I ran 30% E85 to 70% 91 octane and it was fine for a few tanks, ended up switching back just because the E85 station isn't near me. Only thing to watch for is E85 is unregulated on mixture so a cheap alcohol content gauge goes a long way to see if you actually have E85, or E70 etc, and also see the ethanol content in your gasoline, most stations its 10% ethanol added to the gasoline. Any cold weather place may run E70 in the winter as it helps with starting (gasoline has a much lower freezing temperature than Alcohol and E85 can cause starting issues in the winter time, so they run more gasoline in the mix) but with just 25-30% its nothing you should notice.

[535_BiTurbo]

Interested in seeing results as well