[Carl Morris]

I've been on straight E85 for over a month now, and am planning to go back to 91 after Bandimere next Wednesday. This last couple of days of temps in the 30s have allowed me to make a few observations I couldn't make before.

Yes, it's a bit slower to start, but I expected that. If/when Cobb gives us control of the cold enrichment, a lot of that can be tuned out.

At full boost in the midrange it feels soggy. I logged on the way home from work expecting to see flatline timing due to overboost. Instead what I see is wacky fuel pressures. Apparently I'm at the limit of my fuel system on straight E85, whether that's due to a mechanical limit or perhaps some reduction in capacity due to old filters/pickup socks/whatever. I don't notice it in hot weather, but in the cold at 18psi the low pressure side oscillates all over the place between 90psi and 50-60psi. Not enough to set a code, but it looks like it's having a hard time regulating. Then, on the high pressure side, when full boost hits, I'm requesting about 2500psi and only getting about 1900. This wasn't happening in the warmer weather.

I'll be curious to see what Shiv starts selling for the fuel system. In the meantime, if it's this cold next Wednesday I'll probably go faster if I switch to 50/50 to reduce the fuel system load about 20%.

[raceyBMW]

Is that because of thickening of the E85 during lower temps you think?

Curious to see logs if you have them to see what this looks like.

[Carl Morris]

I don't think ethanol thickens in the cold. You will see cold starting issues, I think because it doesn't evaporate as easily in the cold. But because it takes about 40% more volume pumped for the same amount of airflow, it uses the fuel system a lot harder than gasoline. I do have logs, I'll edit one and post it.

[Carl Morris]

It's short, but it's the whole time I was at WOT.

[richpike]

Are you running 100% for convenience? It seems like most the dynos I've seen peak on power around a 50/50 mix.

-Rich

[Carl Morris]

Mostly as an experiment because I can since Cobb made the scalar value accessible. I agree that you get most of the gains with 50/50, but I am able to run a bit more timing with 100%. I'm curious if most of the people who peaked at 50% were able to try more? Unless they were running a Cobb they probably couldn't.

[richpike]

Cool. IIRC, I've read of a few folks running the Vishnu DME flash and dyno'ing at 50/50 and 100% and not seeing too much gain, but just bring able to fill up with 100% E85 would definitely be ideal.

On a random, but related, note, is there anyway to tell if someone has run E85? EG, is the gas a different color, etc? Or would the dealer have to do a fuel test?

-Rich

[Carl Morris]

As far as I know the only way to tell is if they still have a higher than normal concentration of ethanol in the tank. Once it's all burned out and you're on straight gasoline I think you're good.