Donald

The Gunk thread is very interesting as well. I learned a few details there. A petroleum expert chimed-in w/some interesting facts

 

 

It's a bunch of things from PCV and EGR to old fuel buildup in tanks before coverting to store E85 to stations mixing their E85 with gasoline that has non-compatible additives. I'm more confused after skimming through that other thread.
Razorlab had opposite results regarding the PCV and EGR, so that leaves old tanks and improper mixing with non-compatible additives for high ethanol concentrations. Please don't make me read again. LOL.
Update: I think it was MrFred, not Razorlab (after seeing his post below. Lol)

 

Here is a summary of the problem.

The most accurate answer we have received IMHO is this pasted here: (Its starts on page 9)
The deposits primarily consist of "Poly Iso Butylene," or PIB, a cleaning additive in the gasoline portion of commercial E85 blends. As far as we know, the ethanol itself doesn't directly cause this type of problem with injector and valve deposits. This PIB additive was never designed for use in high ethanol concentrations.

PIB is designed to soften engine deposits, but below a certain concentration (by total fuel volume) it is actually counter-productive. What happens is that with insufficient PIB by volume, the normal valve deposits don't soften. The PIB actually combines with these normally occurring deposits and makes build up worse.

Running PIB-free E85 is basically impossible in a practical sense. GM engineers ordered special batches of PIB-free E85, but in the real world the E85 still becomes contaminated with PIB because the entire fuel refining and transport infrastructure has traces of it. Still, with this very low PIB concentration E85 deposits can still occur at similar rates.

 

The important thing is that we all understand that using E85 comes with a risk. For me, I will use it as desired (track days) and not all the time.

 

The problem with switching fuel is that it will always be a blend. My local station is actually E79. And if I switch when low fuel light comes on, my mixture will be about E67. If I keep driving for another 15 miles after low fuel light, I'll have something like E73. Our dual map tune needs to be good for E65 to be safe and rich enough to work with true E85 (is that 23% richer?). So if we are tuned to 12.5 afr on E65, we should be at 11.9 to account for true E85? And do we add a little cushion for injector clogging?

 

Putting that into context though, if you are aware of the risks, and take proper steps to mitigate them, then arguably and IMO the benefits far exceed the potential risks.

 

I think you raise some really good points in that what alot of us are using is basically a hacked solution. If your not the kind of person that wants to deal with all the misc. steps, issues, or gotcha's that come along with that then it would probably be a good idea to get a true flex fuel setup like a stand alone EMS that is designed to just handle all this automatically.

So IMO if you wanted to run E85 all the time with a stock ECU you should at least be able to interpret logs, and be willing and able to make adjustments on the fly in ecuflash to your tune.

 

I can say for sure that its not PCV, EGR, or old fuel buildup in fuel storage tanks. My Evo has neither PCV recirculated into the intake manifold nor EGR, and the station where I buy E85 goes through their entire 3000 gallon supply of E85 every few weeks (they supply E85 to all the local govt vehicles), so there is no old fuel build up in the tank, and yet my Evo definitely has a gunk problem. Everything I have read indicates that the issue is due to chemicals in the gasoline that is mixed with the E85. It could be one of the additives or it could be high levels of gum that are a byproduct of the gasoline production. I know for sure that the E85 provided by my station is created using some off-brand, non-top tier, regular gasoline, so there is a good chance that there is excess gum content or the additives are not the best choice.

 

I wonder if there is a blackstone labs like place, or maybe even them, you could send a sample to for analysis. It would also be pretty interesting to pick the brains of the guys who maintain that govt. fleet.

 

Actually I just called Blackstone and they do offer a variety of tests for E85, free test kit inbound. I was quoted $48 to run the tests.

 

Wonder if they can give you the value of the PIB in solution? & compare that value w/the industry standard for 91 or 93.

As noted, the low level of PIB in solution is what was noted as the causal factor for the "Gunk"

 

I need to dig into what kind of data their tests will provide and hopefully how relevant its going to be. I know embarrassingly little about chemistry so this should be fun.

 

This is an awesome idea. If they can measure PIB and gum levels, that would be great to know. I would definitely send them a sample of my station's E85.

 

In a nutshell ,that's the jist of it.