E85: E70, E74, E80...changing pump mixture a problem for tuning?

[scheides]

How the hell do the flexfuel chevy's do it? I imagine they have a little module in the gas tank or fuel line that measures ethanol content and then adjusts a/f's for it...would it be possible to hook up something like this to AEM EMS and then just use something like the nitrous controls (or something more progressive, not just on/off) to add or remove fuel? Obviously that would be a lot more tuning time, but would be really cool if it would work!

[Shane@DBPerformance]

Yea, there is a fuel composition sensor that tells the ECU the alcohol content and temperature of the fuel. They are expensive though. It can also be done using O2 sensor fuel trim and a knock sensor, but that approach won't be the best on a performance vehicle.

[scheides]

Hrm, so would tuning to straight E85 and then just running rich as the blend changes be an option? Any idea on how this would affect performance?

[Goat Blower]

You could, but like Shane said, knock resistance and cooling properties go down with less Ethanol, so you'd really have to be safely tuned at E85 to make it work. If you're constantly tuning by your wideband, it would work.

There's another thing that has come up when using E85, a lot more poo in the oil overflow tank. Looks like you have to change it very regularly. I think I'm going to route mine directly into the exhaust to take care of this.

[Jakey]

Does an AEM have an input for a fuel composition sensor? I know that a MegaSquirt can be setup as flex fuel.

[Halon]

You could, but like Shane said, knock resistance and cooling properties go down with less Ethanol, so you'd really have to be safely tuned at E85 to make it work. If you're constantly tuning by your wideband, it would work.

There's another thing that has come up when using E85, a lot more poo in the oil overflow tank. Looks like you have to change it very regularly. I think I'm going to route mine directly into the exhaust to take care of this.

Pardon my ignorance, but where is this oil overflow? Do you just mean catch can?

[Halon]

It may not be as perfect as being on a dyno, and being able to actually read the gains on the meter, but I don't see why using a wideband setup and a good functioning knock sensor, one couldn't just tune it decently on the street. I don't feel like paying hundreds of dollars, multiple times throughout the year, to perfect a tune on a dyno. that is going to be changing quite a bit I will go to the dyno to get good tunes once or twice throughout the summer, but in between I will be adjusting it myself when I notice changes.

Also, do you have any links to the way you know to test it?

[rst95eclipse]

My question is: where can you buy E98 then?

[Jakey]

Do you just mean catch can?
Yes. People running high concentrations of ethanol are reporting their catch cans filling up abnormally fast.

[Jakey]

My question is: where can you buy E98 then?
That's the big question. Try to find a local distributor. Swifty's buddy Jake Montgomery has been able to get by the 55 gallon drum out in Idaho. With all of the ethanol we have around here, one would surely think that it could be purchased at high concentrations.