Quote:
Originally Posted by ZM2
Something to keep in mind is we’re on the bleeding edge to find a high Emix that works on the track for long runs. The temps are much higher than the street guys going for big hp on a run or two.
That’s not to say you’re not right, but I can easily run E35 with the stock HPFP on a hot track day. Altho, it craps out on me on E26 below 60F ambient.
Doubtful the xdi 35 can run E85 on the street on a cold day, but maybe it’s enough for a warm track day once the IATs are up? Not sure.
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The best mixture of ethanol would probably be no higher than 85% unless running a top cylinder lube, even at 85% a top cylinder lube is recommended to ensure the alcohol doesnt cause corrosion and strip the seals of moisture and lubrication, since ethanol is an extremely effective solvent. The reason why more ethanol is better is because you get the evaporative cooling effect when ethanol burns helping to cool the cylinder.
The amount of ethanol the xdi 35 can support is mainly dependent on how much air your turbo is flowing, more than likely it will not be able to push over E50, and E30 range is where it is probably operating "happiest" and able to meet the fuel demands especially when the ecu fuel dumps when it things egts are too high.
I also looked at your logs, maybe if you targeted a bit richer afrs in the mid to high 11's you would get cooler cylinder temps, generally speaking I always had my cars (subarus and evos) in the past tuned to run richer. But with the new bmw's I am not quite sure where the happy point is with afrs since my main tuning experience with this platform was with a jb4 and bench flashes where you really had zero control over these things. But anyways a richer afr may help you out in keeping cylinder temps lower and thus lower coolant and oil temps.
Note: alot of people are misinformed due to the piggyback tuning scene, that these cars like to run lean and run like crap when tuned to run rich. The misconception comes in because the piggy backs were unable to modify AFR's to make the car run richer so the tuners just said the car hasn't seen any issue running lean (~13 range) so people misinterpret that as the car likes to run lean (it was also probably tuned that way to get better fuel economy especially since these motors are DI so they can get away running a bit leaner as the fuel is sprayed directly into the cylinder). No this is not true, the car has no issue YET, running lean but that doesn't mean it likes to run lean. Next they say the car runs like crap when it is tuned for richer afrs, yes that's true but it's only misfiring because the HPFP is crashing, if you had an upgraded hpfp that wouldn't be an issue. We are lucky with the m2 since bmw has tuned this car to run significantly richer than stock F Series n55's which were regularly hitting the 13 range. But still the afr's do reach the high 12's at times and sometimes do hit 13, and I believe it would really benefit these cars to run a bit richer and never hit the 13's under load. A final thing to note is that I am not talking about off throttle and idling afrs which are fine to be lean, as you wouldnt want your car idling super rich burning fuel for no reason.
As a final rant there is so much misinformation spread by the piggy back tuning world since it was the first method of tuning for these cars that it really does bother the crap out of me. The most famous one is "how much meth do I need to hit X amount of power"....... The misconception with this is that people dont realize that with this platform the meth is supplementing fuel, and you can make the same power spraying distilled water as well (factoring in the fact that you have sufficient fueling), or spraying more 50% meth, instead of the popular trend of running 100% meth which really is only heard of on the bmw platform. This really bothers me when I hear you need 100% meth to hit the power level and water isn't helpful meth is, while in reality you need more meth because the car needs more fuel.