e85
 

Whats the difference internally on an engine that can run it and one that cant? What if I did anyways?

There are several changes made to engines that run E85, but pretty much any gasoline engine CAN run it. It just doesn't run it as efficiently as an engine designed for E85.

E85 engines have:
- increased compression with compression ratios in the mid to high teens
- have different ignition timing
- larger injectors
- run at a different air/fuel ratio than gasoline

Those are only some of the differences.

So a car that can run both changes ignition timing and air fuel ratio based on whats in the tank?

Correct. I believe the flex fuel vehicles have a sensor that basically tells how much of the fuel is ethanol vs gasoline. From there, it can guestimate ignition timing and AFR.

Could it be the o2 sensor is different for the flex fuel version of my vehicle?

The ECU determines what *kind* of gasoline it's using by:

1) electrolysis-analysis of the gasoline (older ECU's)
2) ignition-advance and "ping"-analysis (newer ECU's, especially with turbo's).

I think the sensor to detect are gone now I think the car figures it out (GM anyway) more or less by long term fuel trim. For the most part as long as your LTFT doesn't get to high you won't get a check engine light.

I blended some E85 Monday in my Cobalt XFE(non-ffv) and was around E55, after about 40 or so miles it threw a CEL, put in a couple more gallons of E10 when I could and brought it down to E45, light stayed on, next day 3 more gallons of E10 for E35 and the light cleared itself.

http://www.speedperf6rmanc3.com/cont...evel_Study.pdf

Interesting read on ethanol blends and non-FFV cars. I've had 50% blends in all my cars without any issue other than an occasion CEL

http://cumminsengines.com/uploads/do...nal-report.pdf

Here's another good read. Planet e85 has some info on conversion kit and conversions just using larger injectors to avoid the CEL.

As said, newer cars can adapt more easily to e85 because of the variable valve timing, cam phasing, lift control, turbo charging, direct injection, etc.

The only real changes, today, are in the programming.

Agree, IMO every car sold in the US should be Flex Fuel, nothing like competition to make everyone better.