[Saaaan1]

I have a 2008 E92 335xi coupe (n54, 300bhp) that has zero modifications. I am curious to know whether or not my car can use E85 without causing any issues or malfunctions. If I can run E85, I would probably only do it once every few months. Would I gain any power increase from doing this? And at what ratio of E85 to 93 oct would maximise the power output? Thank you!

[lookalikehuuh]

I presume you are talking about not doing any tuning and just adding E85 on your stock N54?

If this is the case you will see little to no difference at all unless you have low quality fuel or something in your area causing lots of timing corrections on the stock map.

General rule of thumb is that as long as you have a healthy low pressure fuel pump and high pressure fuel pump you can safely run about E30ish level blends without having to upgrade the fuel pump to Stage2.

[Saaaan1]

Originally Posted by lookalikehuuh

I presume you are talking about not doing any tuning and just adding E85 on your stock N54?

If this is the case you will see little to no difference at all unless you have low quality fuel or something in your area causing lots of timing corrections on the stock map.

General rule of thumb is that as long as you have a healthy low pressure fuel pump and high pressure fuel pump you can safely run about E30ish level blends without having to upgrade the fuel pump to Stage2.

So can I put say 30% E85 and 70% 93? Or should I use e30 gas with the same ratio

[Saif2018]

Originally Posted by Saaaan1

So can I put say 30% E85 and 70% 93? Or should I use e30 gas with the same ratio

If your car isn't tuned, E85 is a complete waste of your time and money.

You also log to ensure your LPFP isn't dropping too low, for which you will need MHD

[lookalikehuuh]

Originally Posted by Saaaan1

So can I put say 30% E85 and 70% 93? Or should I use e30 gas with the same ratio

Its somewhat more complex than just adding 30% E85.

So first, you MUST test the E85 content level, E85 ethanol levels can vary from 51% to 83% depending on the season and region of the country you live in. For me in SoCal we just about always get ~E83 at the pump. In Chicago I'm pretty sure you guys will get pretty big differences depending on the season of the year.

Second, you have to keep in mind that most 93 gas stations today already use ~10% ethanol in fuel so you must take that into your calculation. I actually test the gasoline every time and I've seen about 7-10% ethanol at my Shell station.

Once you have both of those number you MUST use a calculator to figure out how much of each fuel must be used to make an approximate proper mix. On my Android device I use an app called "E85 Mix Calculator" which works great. No idea what a good app would be for apple devices since I don't have one.

Keep in mind every time you fill up you have to factor in how much fuel you already have in the tank before filling up or your mix will be thrown off pretty quickly. I've determined that each "line" on the fuel gauge in my car is approx .75 gallons so that's what I use to calculate approx fuel level before filing.

Example of Mixes depending on the season:
Summer: E85 with 83% ethanol, Gasoline with 10% ethanol and 1 gallon of fuel already in the tank that is already E10: 4.36 Gallons of E85, 10.54 Gallons of 93.

Winter: E85 with 51% ethanol, Gasoline with 10% ethanol and 1 gallon of fuel already in the tank that is already E10: 7.76 Gallons of E85, 7.14 Gallons of 93.

Again this is NOT WORTH IT if you aren't tuned and could cause issues for your car since ethanol requires more fuel for the same combustion than gasoline so your car will have to try to compensate. If you tune your car to stage 1+ or Stage2+ with supporting mods then that makes sense but not as much for stock vehicles.

[iqraceworks]

Without getting too technical....NO, you can't run e85 in your car without a tune. Even with a tune, running straight e85 is pretty much worthless since the fuel injection system can't keep up with the flow required (stoich for Ethanol is around 10:1, gasoline is 14.7:1). You need a lot more e85 to get a proper mixture vs. gas.

With a tune and a larger LPFP these cars can run an e40-e60 mix....and that does add power with a proper tune.

Do some research 👍