MegaSquirt FFV use?

I wonder what exactly is the difference in terms of ECU operation? Is the stoichiometric ratio different for E85? If not, then it's all a matter of properly adjusted injector pulse widths

Peter

E85 is 85% ethanol, so the ratio, and also the curves are different. Most engines can be operated much closer to stochiometric on alcohols than on gasoline, which is why Lycoming aircraft engines only burn 20% more ethanol than avgas rather than the 40% heat value dictates.

ALso you ideally want to be able to run on any arbitrary mix from 100% down to 15% gasoline so that you do not need to have separate fuel systems or purge them when switching fuels.

You must also have higher flow injectors of course as they may be called on to deliver at least 40% more fuel at WOT.

Most Lycoming aircraft engines are air cooled. Many people do run aircooled engines slightly rich, though in most aircraft the engine controls include a mixture control, so the recommendation is to run rich during high powered operation such as takeoff and then lean mixture for cruise.

Modern liquid cooled automotive engines run quite close to stochiometric. Interestingly, gasoline must run pretty close to stoch ratio to burn well, but alcohol allows operation on a VERY rich mixture without ignition problems (ratios gasoline would not light off at). Thus in race cars the engines are frequently set up VERY rich.

Yup, 1938 technology. Although TCM (Continental) built some liquid cooled flat engines all Lycoming aircraft engines in series production are air cooled. The pilot has to ba a FE also and run the powerplant, which should be outlawed, but that's another story.

Moreso with methanol than ethanol. Using water injection works even better but efficiency isn't the point in racing.

As Dave Blanton said, "all engines are liquid cooled...."

Flexible Fuel with MegaSquirt-II has been one of the things we have been working on. Al will be releasing the latest production code revision which has full FFV support within a few days.

For more info see:

- Bruce