Originally Posted by arghx7

Hi,

Chemical Origins of the Deposits

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.

A lot of people on here have speculated something along these lines.

Effect of Drive Cycle

Deposit formation is highly dependent on vehicle use and overall drive cycle. This whole issues is complicated, but aside from the makeup of the actual E85 blend, drive cycle is the #1 factor in these deposits.


Bergstrom, "The New ECOTEC Turbo BioPower Engine from GM Powertrain," 2007, Internationales Wiener Motorensymposium 2007, p. 29

On the left is a multi-hole type (not pintle type) fuel injector after 15,000 km running a GM in-house designed drive cycle to simulate major stop-and-go city driving. On the right is the same type of injector after 60,000km in a high-speed (mostly highway) drive cycle. Both engines were running the same commercial E85 blend in Sweden, consisting of 95 RON fuel and denatured ethanol.

Drive cycle variations may not explain absolutely everything but it is a reasonable hypothesis for why two vehicles running the same E85 blend can have such variability. This can also partly explain why somebody doing a lot of highway driving (rural driver or suburban commuter) who always runs E85 may never experience noticeable deposits.

Using Fuel additives and Normal Gasoline blends

There are a lot of fuel additive blends out there and they change all the time so I can't speak for all of the various formulations. What we do know based on GM's research is that PolyEther Amine or "PEA" , which can/used to be found in Techron products, cleans valve deposits but does not clean injectors with this problem. In fact, too much of fuel system cleaner could make the problem worse.



So how do we clean up the deposits if an engine is prone to them for whatever reason? Put "normal" gasoline blends in the tank and it will go away within 1 tank. You don't even need to pull the injectors.



Most of you already knew that. It's not really news; it just confirms with reliable sources what has been widely understood.

Conclusion

So yes, I didn't have any earth-shattering solutions to present, but I did clear up some of the mechanisms for this deposit formation. The deposits are caused by the gasoline portion of E85. The two biggest factors in deposit formation are the additive mix in the fuel and the way you drive the vehicle. Fuel system cleaner products are innocuous at best, counter-productive at worst. The type of injector or fuel system you run might matter some but they are not part of the mechanism of deposit formation.

So if you figure out that your engine is prone to these deposits, be mindful of stop-and-go traffic and put gasoline in your engine sometimes to clean it out.

Hope that helps.

Originally Posted by mrfred

I just re-read the thread. Cliff Notes is that appears to either be a gum in the E-85, or if the E-85 is being placed in old diesel tanks, its something from those tanks.

I'm pretty tempted to try out some of the fuel system cleaners rather than run a tank of gasoline.

Originally Posted by Svendiesel

Yes I'd be interested as well, but Im timid because Ive seen that 93 works rather efficiently. I guess Im gonna have to run 93 thru every 2 or 3 tanks now instead of 500 miles.

My PCV is deleted I dont recirc to my intake mani, I just run an open catch can setup

Originally Posted by Svendiesel

That study shows that additives can worsen the problem whereas regular fuel does the job properly.

Why would we use additives then when regular fuel can do the job?


I wonder what the hell can be done for keeping the intake valves clean though.

Originally Posted by mrfred

Thanks for reminding me of that article. I decided to do a bit of digging and came up with another relevant article that I've attached. Sorry for the poor resolution in the article, but at least I have it. The authors' conclusions are:

- The gunk is due to PIB polymers from engine oil that is finding its way back into the IM via EGR or PCV. If true, this would be a good reason to disable EGR and not use PCV. Based on thiazole's research posted on CODSM, I think there's a good chance its also due in part, if not 100%, to the additive package in the gasoline mixed with the ethanol.
- PEA-based fuel additives (e.g. Techron or Redline SI-1) mixed with E85 will dissolve the gunk, but running a tank of gasoline works even better.

Originally Posted by boostedwrx

Good article.. still reading it The experiment where they removed the EGR and it reduced the amount of deposits was interesting. Using an additive seems easier to me than other members who want to run pump gas every so often. With the E98 I was running, the deposits were a non-issue. Now that I'm on pump E, I want to watch out for the deposits.

Originally Posted by boostedwrx

^ Is Amsoil PI or Quickshot suitable for E85? Everything I read says gas and E10 fuel.

Originally Posted by apagan01

The real answer is to disable all emissions equipment such as EGR ect....

Originally Posted by boostedwrx

Good article.. still reading it The experiment where they removed the EGR and it reduced the amount of deposits was interesting. Using an additive seems easier to me than other members who want to run pump gas every so often. With the E98 I was running, the deposits were a non-issue. Now that I'm on pump E, I want to watch out for the deposits.