Running B100 -- 3rd Gens -- Polymerization (Flocking) -- Good News.

[67guzzler]

Finally -- I must have burned up the search engines and I have some specific information regarding using B100 in high pressure direct injected engines.

The story is long but I'll try to simmer it down to this. The information about people report "hearing" that there is a problem with running B100 in HPDI engines exists. But after looking at the problem more closely it appears that the fact that it was B100 wasn't the problem at all. It was a fuel quality issue.

Here is the (long) story from "johnbush" on the biodiesel forum:

"A little over a year ago, Boulder Biodiesel was distributing Blue Sun Biodiesel to a transit authority in Boulder who was testing Blue Suns' B100 in one of their buses (known as the "Hop"), which had a Cummins common-rail injection system. Apparently, after months of using the fuel, they were still clogging their fuel filters about once a week, and this was a rather new vehicle so fuel tank deposits seemed unlikely. They had the filters sent to a lab, and determined that a "sand-like" particulate was responsible for the clogging. The lab had stated that there had been a problem with the high pressure of the Cummins common rail injection system causing the fuel to "floculate" forming these particulates. This was occuring in the injection pump, then the particulates were passed through the return line back to the tank, and then the next time they traveled through the fuel system they were being clogged in the filter. I am not sure whether the lab had relayed this message as an official statement from Cummins or if they came up with it on their own. However, the bus was soon switched to run only on B20, which they did not recieve from Boulder Biodiesel, so I do not know what eventually became of it after that."

NOW DON'T FREAK OUT.

There is credible evidence that the problems they had was due to a bad batch of biodiesel from Blue Sun!

Please read this from Mike Briggs on the Biodiese Forum:

"High pressure won't polymerize biodiesel. The polymerization issue arises if the fuel oxidizes into peroxides (i.e. hydroperoxide), which can then lead to polymerization. The navy has done extensive research on this. See one of their reports at http://www.biodiesel.org/resources/r...01_mar-021.pdf
Note that in their tests, they found that the biodiesel they used was MORE stable against oxidation than their diesel fuel. The biggest issue comes down to three things - quality, quality, and quality. And usually, the quality issue comes down to the storage issue. Fuel being exposed to air/water is the biggest culprit in practically every case, due to degradation of the fuel (oxidation, and eventual peroxidation), or in longer-term failures from corrosion.

That navy study has the most thorough data I've seen on oxidation stability testing of B100, biodiesel blends, and straight diesel in a direct comparison."

He goes on to say:

"On the issue of polymerization/oxidation - the iodine number is related to how readily an oil (or biodiesel) will polymerize - but again, it only does so under conditions the fuel shouldn't be in anyway (ie water contamination, etc.). Biodiesel doesn't directly polymerize itself - it first has to be oxidized to form peroxides, which THEN polymerize. So, without the potential for oxidation, you won't get polymerization. Another potential issue - if there are substantial levels of glycerin remaining in the fuel (which ASTM quality biodiesel shouldn't have), you can get acrolein formation from the glycerin, with the acrolein itself polymerizing in combustion chambers. See http://www.deh.gov.au/atmosphere/bio...bs/logical.pdf
for more on this (this is the comments from a VERY highly regarded chemist when Australia started forming its standardization for biodiesel). You can search for "polymerize" to see the parts where he deals with this specifically.

So, ultimately the issue of polymerization should come down to fuel quality. Excess glycerin can lead to acrolein formation and polymerization. Excess water or other poor storage issues can lead to oxidation/polymerization of the biodiesel itself. Injection Pressure by itself shouldn't be an issue - but of course I could be wrong."

So what has started as a B100 and HPDI engine problem is more likely to be a bad fuel problem that was uncovered BY the pressures of the HPDI (Common Rail for us 3rd Genners).

What does this mean to us? The quality and nature of the fuel matters more if you're running a 3rd Gen. The D6751 standard matters more. The microbe content matters more. The amount of water in the fuel matters more. And running pure veggie on a 3rd gen can be more more problematic if you can't control the impurities and water in the oil.

Also -- There is evidence that the polymerization problem is less likely to occur if the biodiesel is animal based such as beef tallow because it's properties are different that plant oils. I'm no scientist but from what I've read some plant oils (soybean for example) is more unstable at a molecular level and will bind closer to water molecules. Our fuel / water separator system isn't as good at removing water from plant oil as it is with petro or animal. Water apparently one of the elements that can encourage this polymerization to occur. Microbes is another. So if one is to use the more common plant-based biodiesel it's even more important that it meets the D6751 standard, doesn't have water and is free of microbes.

I'm a 100% novice at this and it's possible that some of my analysis is slightly off or even grossly off but this is what I have gathered to this point.

Please read more about it in this two page thread at the biodiesel forum:

http://forums.biodieselnow.com/topic.asp?TOPIC_ID=3829

which discuss this thread at the diesel stop:

http://forums.thedieselstop.com/ubbt...b=5&o=&fpart=1

One last note -- More common sense evidence that the bus Colorado B100 Trasit filter clogging problems were more related to fuel quality than HPDI issues is that I found there are people out there running B100 on 3rd Gens / Duramax / Powerstrokes (they approach 30,000 psi) and they're not having troubles. When they do have troubles, they worry it's the B100 but then they often find it is a mechanical problem that others are having with their line / model year of truck. There was a gentleman who had a pump failure on the biodiesel board. It was the pump at the gas tank I believe. Anyway, the poor guy was terrified that the B100 caused it. But when he took his truck in to the dealer they found there were TSB's on the issue with his pump / model year and they fixed it under warranty. Same types of events have happened with the 6.0 powerstrokes. Early engines had lots of problems but when B100 users boiled them down they were usually engine problems that were unrelated to fuel type.

Another last note -- The "damage" caused to this Colorado Transit Authorities Cummins engines was limited to having to change their filters weekly to keep running. Once they went to a B20 ratio with the low quality bio portion of the blend, their problems subsided. But it's reasonable to believe they subsided not because of the ratio of biodiesel is 20% but the ratio of bad diesel was reduced to 20%.

Please let me know what I got right, what I got wrong and what you all think.

Thanks!