Gasohol and AFR., what setting? what impact? Options

[jk76.914]

I'm still working through my 2500 RPM shudder, and so I'm about to invest in an true wide-band O2 sensor and AFR reader machine. As I calibrate my MPS on my D-Jet, what should I calibrate it to for gasohol?

(I'll keep updating my progress on the shudder in my other thread. This was deserving of its own topic, methinks)

Seems like ALL the stations around here are switching or have switched. I'm pretty sure I have a full tank of the stuff on board now, and my paranoia is questioning whether the switchover hasn't hurt my 914's driveability.

Some facts-

1. a number of car manufacturers warn against starting problems and hot driveability problems. They say that if either is experienced, switch back to 100% gasoline. (Hyundai, Toyota, Lexus, Volvo).

2. They say DO NOT use gasoline with more then 10% alcohol, unless the vehicle is specially designed for it, like the Ford FFV tauruses, etc. Also, DO NOT use gasohol made with methanol, only ethanol.

3. Stoichiometric air-fuel ratio for methanol is 9.0, vs. 14.7 for gasoline. This means that although methanol has less energy per gallon than gasoline, you use enough more of it, assuming you're tuned for it, that your engine will deliver more power, albeit at the expense of higher fuel consumption.

4. Effective octane rating of methanol is something like 113. But since you buy it from a pump labelled 93 octane, you can probably bet the oil company already took advantage of the higher octane and mixed it with some cheap pissy gasoline and is still delivering you the 93.


More interesting stuff here.....

http://www.ext.colostate.edu/Pubs/farmmgt/05010.html

Back to my original question- where should I set my MPS? I found a thread at a Corvette forum website, that recommended 11.7 AFR for gasohol for peak power, vs. 12.5 for gasoline. Anybody have any better info than that????

thanks!
Jim

[jk76.914]

3. Stoichiometric air-fuel ratio for ethanol is 9.0, vs. 14.7 for gasoline. This means that although ethanol has less energy per gallon than gasoline, you use enough more of it, assuming you're tuned for it, that your engine will deliver more power, albeit at the expense of higher fuel consumption.

4. Effective octane rating of ethanol is something like 113. But since you buy it from a pump labelled 93 octane, you can probably bet the oil company already took advantage of the higher octane and mixed it with some cheap pissy gasoline and is still delivering you the 93.

Oops. I meant ethanol in these three places. No responses? Maybe I'm on my own here, eh?

Jim

[fiid]

Hey,

I don't know what the ratios are, so I'll take your word for that...

I do know that there are FlexFuel sensors available, and the megasquirt has some hooks for those sensors. The 914 injectors are supposed to be well oversized (makes D-jet work), so it wouldn't suprise me at all if you could get a megasquirt running with the correct sensor and auto adjusting your mixture..... (IMG:style_emoticons/default/biggrin.gif) That would be a sweet setup.

[Mark Henry]

We use it here, very little effect, about .3 on my WMS wideband

Although ethanol has a higher octain it does burn slower than gas and one nice bonus (for us) is that it runs cooler than gas.

To me it's a non-issue.