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Bko
08-26-2016, 09:24 AM
This is more of a general discussion not expecting to getting answers given to me.

In the B8 S4 forum there a discussion on mixing E85. Looks like its common to run a 30/70 mixture on other places on the internet.
I currently run the Aeb PC-16 tune with a 3 bar FPR. Most people say they found it best to run 2.7-2.8 bar. I look into it but how does FPR affect fuel deliver?

Is there a way to calculate the difference between the 3 bar and 2.7bar. Some numbers I have found online say you need 30% more E85 then regular gas.
Using said calculated numbers could you safely use E85 to get to the fuel delivery of the 2.7 bar using the 3 bar and e85.

Also
I have the race tune (100 octane) could I just calculate for a 30% larger injectors and run straight E85. Being that E85 is close to 100-105 octane. I would think the timing maps for the race tune would be close to what an E85 tune would be? Pry making this to simplistic.

Im going to look into this more, but figured it might be a interesting discussion.

redline380
08-26-2016, 09:27 AM
If you are going to run e85, you need more fuel. Adjusting the regulator is not the proper way. I mean you could potentially cheap an eye on AFR's, but EGT's would probably be out of hand.

Seerlah
08-26-2016, 09:45 AM
Playing the guessing game with fueling is not a smart idea. Worst case scenario, you blow your engine. Not sure worst case...use your imagination. But I can just about guarantee your car won't like it. If there is a concrete formula with the 70/30 ratio, then it would first need to be applied and tested to our car. If you are willing to let your car be the test car, this is how info gets created and spread for another to soak in.

Davdraco1
08-26-2016, 10:00 AM
I thought E85 was closer to 115-120.

MetalMan
08-26-2016, 10:06 AM
I currently run the Aeb PC-16 tune with a 3 bar FPR. Most people say they found it best to run 2.7-2.8 bar. I look into it but how does FPR affect fuel deliver?

Is there a way to calculate the difference between the 3 bar and 2.7bar.

Fuel pressure is related to fuel delivery. There are calculators available online. FYI injectors are generally given their CC rating @ 3bar.
http://www.deatschwerks.com/resources/fuel-calculators/flow-vs-pressure-calculator
So for example on the PC-16, if you're running 315cc injectors @ 2.7bar, actual fuel delivered is 299cc.

redline is right, you can't just increase fuel pressure for E85 to increase fuel availability to sufficient levels. (you would have to run 5+ bar fuel pressure to achieve 30% higher flow compared to 3bar, and this isn't wise)

Running E85 on AEB is tricky. AEB is narrowband, meaning it reads a very small lambda (AFR) range right around stoichiometric. It's much safer to run a wideband when tuning for E85, like what comes on the AWM. You may be able to find a tuner who will tune for E85 on AEB if you have a separate wideband gauge, though.

In conclusion, don't just increase fueling 30% for running E85 and determine that it will be "safe". This is just asking for trouble.

Rodgman15
08-26-2016, 05:13 PM
I run e85 and e98 on AEB. Added a wideband gauge to use for tuning. I also use Maestro 7 which made fuel adjustments easy. Ended up adding roughly 25/30% fuel across the board relative to a pump gas tune. With that being said, you need injectors with that kind of headroom.

walky_talky20
08-28-2016, 11:39 AM
Guys, I think you may be missing his point.

OP does not want to run straight E85. He just doesn't.

OP is running a PC16 tune with a 3 bar FPR, where 2.7 bar is actually recommended. So he is too rich.

OP is wanting to run *some percentage* of E85 to bring down his effective fueling down, instead of actually dialing the pressure back to 2.7 bar.

OP is wondering (A) if it can be mathematically determined what that percentage might be, (B) if this mixing business is safe, and (C) if it will perform the function he wants.

OP thanks you for your input.

Bko
08-28-2016, 06:32 PM
Guys, I think you may be missing his point.

OP does not want to run straight E85. He just doesn't.

OP is running a PC16 tune with a 3 bar FPR, where 2.7 bar is actually recommended. So he is too rich.

OP is wanting to run *some percentage* of E85 to bring down his effective fueling down, instead of actually dialing the pressure back to 2.7 bar.

OP is wondering (A) if it can be mathematically determined what that percentage might be, (B) if this mixing business is safe, and (C) if it will perform the function he wants.

OP thanks you for your input.

This is exactly what I am thinking.
I probably should have not thrown in the part about the 100 octane tune this may have clouded my intentions.
'
I haven't thought of a method to calculate the ratio, but i've been busy this weekend so i haven't looked into it in much detail.