Thread: E-85

If I can find E-85 locally I will run it. We'll see how it goes.

i had an e85 tune done on my car, the car runs about 25% richer at idle under o2 sensor control and the exhaust fumes are to die for runs about 30% richer through the fuel map and takes about 8 to 10 degrees more spark timing.

apparently, the easy way is to adjust the injector k value 25% large to make the base injector pulse larger and then fine tune the k value until the idle mixture is burning at 1.0 lamda with o2 sensor disconnected and then adjust the fueling maps and then start winding in more spark advace.

other side effect is the larger amount of exhaust gas volume helping to spool turbos up quicker at highway speeds, the engine is producing so much extra torque that fuel economy is about the same. around town it suffers a fair bit though.

This was after the tune? Why so much richer? Can it not be adjusted?

Its all about the lambda value. With petrol, 1.0 lambda is at 14.7 to 1 but E85 likes around 10 to 1 for 1.0 lambda. most good wideband o2 gauge can read out in lambda for this reason. on boost, you should be on around 0.85 lamda. its all about oxygen content in the exhaust.

if you run e85 the same mixtures as you run petrol, its the equivalent of running stupid figures like 20 to 1 on petrol... too lean and your engine goes bang.

e85 has less energy in it too, so you need to use more of it to make the same power as well. wikipedia has heaps of info on ethanol fuels as well.

Just so no one is confused by VeryQuikSSS's posts, technically the car doesn't run any richer on E85. Or it shouldn't if properly tuned. Actually, because of the higher anti-knock index, you can run leaner than you normally would with gasoline if you felt like it.

"Lean" and "rich" typically refer to having more or less fuel than stoichiometric. This means that with gasoline, if you have an AFR of 14.7:1 your mixture is technically stoichiometric. With E85, as mentioned, the stoichiometric mixture is 9.765:1 which means that you need much more fuel per air molecule to reach a "perfect" combustion.

While the car will need more fuel with E85, technically it's not running "rich" as VeryQuikSSS has described. It just has more fuel.

Now, about the air/fuel ratio, and tuning. Tuning with a wideband sensor and E85 is effectively the same for both gasoline and E85 because the oxygen sensor reads unburnt oxygen, and doesn't care at all what fuel you use. If your Wideband displays lambda, good for you. You can use 1.0 lambda as stoichiometric as you always have and call it a day. You can also feel warm and fuzzy inside knowing your display is technically accurate too.

Those with displays that show air/fuel ratios instead of lambda like "14.7:1", "12.0:1" and "15.5:1" can tune the same exact way they always have as well. While technically the air/fuel ratio while running E85 might be 9.765:1, the display will show "14.7:1". This is technically incorrect, but completely useful and easily interpreted if you just assume you're using gasoline, and use the values you've always tuned to. This means that you can tune to "12.0:1" ratio on the gauge and it will result in the proper amount of fuel being delivered for boost whether you're running gasoline, E85, propane, hydrogen, etc.

I am proud of you BenFenner, you are doing your homework and it is starting to show.

Tuning is something I know a bit about.

^Interesting post above. Nice info.

Very useful information guys. Guess I will try some tuning with E85 as my air/fuel (zeitronix) reads lambda as well.

My tuner explained everything to me when he put the e85 tune in so I have the basics as i manage to fine tune my car with some logging on long trips and the occoasional track day. sorry about my noob terminology but its how i had it explained to me .

gained 18% on the dyno with a back to back run from our premium pump fuel then e85 with the ecu flashed between runs and fuel swapped out. not a bad gain when e85 was 45 cents per litre cheaper here when it was released.