Problem that i've had is there is a lot of range the fuel content can be. For example it can be as pure as 50/50 mix and up to 90% ethanol.

 

Ahh, no. At least in California, it's required to be at least 75% ethanol (at least where I fill). In reality, there's so much safety margin with a sub-300whp E85 setup that you can just ignore it. For those of us looking for more, it's not hard to fill cans and measure the ethanol content (and then compensate by adding E100 in correct amounts).

 

I've had my afr lean out by nearly a full point after filling up and then richen up by a full point after the next fill up and 13 in boost is bad. 11 in boost is also bad (e85 values)

 

11 afr on the gauge?

 

Brilliant.

For methods to measure E content without getting your hands dirty. I've seen two methods that OEM's have used to measure E content for flex fuel cars. 1 is obviously the flex fuel sensor. They work great, but they're expensive and the ones I've seen go inline in the fuel return line and can only flow a limited amount of fuel. So if your fuel pump flows too well you will have idle issues.

2nd method is a lot more sneaky. They let the car run in closed loop till the long term fuel trim evens out after filling up and then you know how much fuel you needed to add or subtract and you know the stoich of the fuel previously in the tank, so you can determine the stoich of the fuel in the tank. OEM's actually have a look up table for it in the ecu. And with either option in a flex fuel car it will interpolate between the e values (could tune to either e85 or e98) and the gasoline values for commanded lambda, timing, etc. Of course for the straight gas to e85 switch you'll need fuel trims with sufficient range. And if you're using this method manually, dear god stay out of boost until you compensate it.

 

Correct, you can use the standard wideband however tune for different goals (change your tune to accommodate for the new afrs during closed loop) . In boost tune for 12-12.5, 13.5 at 80kpa to atmo and then 16-17 at cruise.

Problem with E85 is sub 11 you might start see pre ignition.

 

absolutely not true. at least not with the stuff we use here. I tune for mid 11's no matter what

 

You're just wasting fuel. I was tuning to ~12.2:1 on E85. Actual AFRs are somewhere in the 8-9:1 range, but my head works in gasoline AFRs so I don't bother switching the wideband translation.

 

I think most of 18psi's E85 tuning is done on Subaru's which might like a little bit richer mixture than mazdas?

Just a guess...

 

I'm not sure how much fuel is wasted between 11.6-11.8 and 12.2 but I'd guess not that much.

And you're right, I'm probably being too conservative staying in the 11's but better safe than sorry. (esp if there is a swing/variation in batches of e85)

(and yes most my tuning is on Scoobs)

 

By "wasting fuel", I mean you're just dumping it into the crankcase and diluting the oil faster than necessary. It's not good or "conservative" or whatever, it's just sloppy tuning. Figure out where it makes the most power and run it there - there's absolutely no need to dump bucketloads of fuel when using E85.

 

So you tune for 12.2 and I tune for 11.8 (just check my fxt maps) and you're saying that .4 afr is the difference between dumping buckets of fuel and a non-sloppy tune? LOL ok.

I'm not arguing with you, its just you're bashing my targets when the difference isn't even significant....And on cars that love to run richer.

Thanks for the input. I actually do plan to experiment with much leaner mixtures on my current miata.

 

11.8 doesn't sound like mid 11s to me. Sounds closer to just under 12.

As far as cars that love to run richer... its not about the car.. its that the fuel igniting while being compressed because its so rich.

 

Not sure if trolling or really that stupid. In any case, I'm not going to waste any more time on this argument. Carry on.

 

Hi

I have no experience tuning E85 on Subaru motors.

But clearly, you are doing it wrong.

I don't care how many reliable, 350+awhp Subarus you have tuned, you obviously have no idea what you are doing and you are a sloppy tuner at best.

Eff you

 

In his defense. Tuning subies rich is common practice. You'll see tunes that people pay good money for commanding as rich as 10.5:1 on 93 octane tunes. I think they're being silly and its way to rich. BUT the fuel mixture thats going to make the most power depends on a metric **** load of factors like combo chamber geometry for example. People think you've built a grenade if you've tuned leaner than 11.

 

I want to see you actually tune any car, much less a modern turbo subaru, and get back to me about what's silly and what's not.

dumbass

Even with miatas there's a whole bunch of peopele on here who pulled out pistons scorched and melted around the ringlands/tops from lean mixture.

 

I apologize for jacking this thread. My posts must seem non sequitur. I know, I should start my own thread that has useful E85 information, mea culpa.



Here is a baby bottle that requires no math:

Echecker - E85 Fuel Test Tube

 

 

Neat widget!

Ok, so how are you bastards even finding E85? Is there some magical website that I'm unaware of that will direct me to this nectar of the gods?