I am convinced after reading this article, that GM KNEW there were problems with their injectors as designed BEFORE production had begun, because they had installed a cooling coil on the fuel return line to the fuel tank thereby acknowledging a problem exhisted and a "solution" to the problem was to "cool the fuel" rather than mitigate the generator of the source of the problem.

According to this article, heat build up bubbles and cavitation in hydralic fluids (diesel Fuel) should have been recognized and addressed as the SOURCE of the problem rather than dealing with sympoms of the problem. This article states that bubbles in fluids causes the fluid to build up heat.
What they did is they delt with the SYMPTOM and NOT the CAUSE of the heat build up i.e. the CAVATATING injectors. Thus, IMHO the more fuel that is put through the injection system per time period (gallons per minute per rise in fuel temperature build up) should exhibt a correlation in injector failure, and NOT necessarily hours on the engine.
This article also points out that pumps also suffer damage form bubbles in the oil (fuel), thus the new replacement procedure to include injector pumps when readings occur outside the normal parameters.

http://www.getottenassociates.com/pdf_files/Bubble%20Eliminator%20Paper%20for%20FP%20Expo%2020 03.pdf

A poorly written article pitching a product that is not needed on any properly designed hydraulic system. Our stock system is properly designed and works fine until it is modified. The only part of our system that will experience cavitation is the LP transfer/booster/pre-charge or what ever you choose to call it pump. Later! Frank

Cavitation :The sudden formation and collapse of low-pressure bubbles in liquids by means of mechanical forces, such as those resulting from rotation of a marine propeller.

Usually on the trialling edge. I don't know that a valve or spray nozzle could cause this.. (injector) This could and does happen in a centrifugal pump (prop). I don't think it could happen in a positive displacement pump. I do believe the injector pump is positive displacement type pump.

This is just my opinion.... And a term definition.

It happens in all types of pumps where the net positive suctions head (too much vacuum) exceeds the design limits of the pump. We have been down this road ten times in the last few years. Later! Frank

It's a significant issue in a mechanical injection system where the pump "strokes" an individual injector and injection line up to 2,000 psi for every injection. Not so much in our high-pressure-common-rail system where the pump drives a pair of injection logs up to 30,000 pounds and holds that pressure for an electronically fired injector. The logs are a reservoir of highly compressed fuel that mitigate the effects of cavitation in the 2 stages of the injection pump. The cooler is to remove the high heat of compression from the difference in pressure, NOT a cavitation symptom relief.

I agree with Tom. The fuel rails are pressurized at full injection pressure. This negates any drastic pressure fluctuations in the mechanicals after the high pressure pump.

If there is entraned air in the system after the high pressure pump, it most likely will remain entrained/dissolved under the constant 5000-23,000 psi condition. That is what the injecter recieves.

The wierd thing is seein 03 trucks with 10,000 miles or less losing injectors. Doesn't make sense that dirty fuel, air or any kind of erosion is the culprit in these cases.

Cavitation should be minimal or non existant in the rails or HP areas of the injectors anyway as any vapors should be returned to solution immediately after leaving the pump. I feel (can't prove) a lot of wear within our injectors would be predominately targeted at the fuel return area of the injector where there is a rapid pressure drop from extreme pressure and the now hot fuel quickly returning to its vaporization point. Injectors SHOULD be designed to handle this but with the high fuel return rates being one symtom of injector failure it has me thinking........

Edited! Boy I had this one screwed up.

Therez sum smart sumbiatches here......

The high leak back rate is just indicative of a blown sealing surface in the injector. All high pressure systems that have a moving part that penetrates the pressure boundry will have some leak by. A sudden increase indicates a crack in the sealing surface and gradual increase indicates wear.

Also, cavitation is NOT air bubles. It is vaporized liquid. Once cooled and pressurized, it will become liquid again.

To illustrate how powerful cavitation can be, l recall water cavitating through the spillway tunnel of Glen Canyon Dam about 15 years ago causing extensive damage to the concrete lining of the tunnel. There were emergency repairs made to prevent further damage to the tunnel in subsequent years. If I recall correctly that there was consideration given to lining the tunnel with Steel Plate.

The point being there was insufficient testing of the injectors. Dirt (4 microns) only aggravates the the collapsing gas bubble instead acting like a sand blaster. Thus better filtration of the fuel only delays the inevitable damage.

But.... is there a cavitation occuring for sure?

The wierd thing is seein 03 trucks with 10,000 miles or less losing injectors. Doesn't make sense that dirty fuel, air or any kind of erosion is the culprit in these cases.
Lack of lubricity would cause injector failures at 10k or less. During "infancy" greater lubricity is required for break-in. Look at the chart on page 12 of this presentation from bosch...

http://www.arb.ca.gov/fuels/gasoline/meeting/2003/022003bosch.pdf

The black line on this chart shows wear when using fuel with poor lubricity - extensive and accelerated wear at 300 hours. It's for pumps - but assuming injectors would wear similarly... With average hours/miles listed by most here - that would put you at about 9k miles... ballpark.

This presentation shows that our trucks will not run reliably on available fuel. Period.

The only way things will get better is if we all start writing the EPA and CARB and demand that they put a lubricity standard in place that protects our trucks. GM is just stalling - hoping that the new fuel standards will kick in and save their butts...

- jeff

Jeff,

interesting article you found there...I can confirm that I am not hearing any issues with all the Diesels that are so popular over here in Europe.
As soon as I have my Duramax I guess I have not much to worry about when running it with the Diesel sold here.

:D:D:D Lucky me :D:D:D

On the other hand I am paying about twice as much for it ....-:t-:t-:t

Therez sum smart sumbiatches here......
I would like to publicly state for the record that I am not one of these. However I read an article that cavitataion can/does occur in the injectors themselves and appearently the higher the pressure the more impact it can have. It sounded like it was very difficult to actually determine to what degree an injector design might have this problem due to their small internal sizes. They (the company desighing the computer modeling software) were developing computer models to try and see it.

The cavitation that seems to be a problem for our injectors is happening in the nozzle orifice. The machining process used to make these super tiny holes leaves an irregular surface on the inside of the orifice and is where the cavitation is taking place. The pressure and flow through the orifice is very high. Any irregularity increases the wear but coupled with cavitation as the fuel tries to go around the imperfection, the wear is very fast. Symptoms will show up in the balance rates.

This has nothing to do with bubbles in the fuel or lubricity of the fuel.

I didn't make the grade for smart sum 'o bish either.

Also, cavitation is NOT air bubles. It is vaporized liquid. Once cooled and pressurized, it will become liquid again.

MMMM the definition I gave is right out of the book. To be more specific, cavitation is GAS bubbles formed in an area of decreased pressure, these bubbles then implode and the temperature increases ~1100 degrees C. When the implosion happens next to a surface there is a thermal transfer of heat melts the surface at a microscopic level. This is where the erosion comes from.
With this in mind, cavitation could happen anytime there is a sudden change of direction. Seems like the pump would have more troubles then we have heard about.

On Edit - Yes, I also fall into the DUMB DUMB category! :)

Cavitation is simply a term used to describe any condition where a "cavity" or void manifests itself in a fluid, & it can be caused by many things. But as stated previously, it is the collapse of this void & the resulting shock wave produced that is responsible for the majority of damages related to cavitation.

Low pressures &/or insufficient volume can create cavitation (for obvious reasons), & once present (it doesn't just all go away nicely), high pressures significantly contributes to its destructiveness (by increasing the shock wave pressure value upon cavity collapse)

Knowing this, you can see where the duramax common rail system (as presently produced) may have its drawbacks (hey, nothings perfect). After having my injectors replaced at 30k though, I took a hard look at this system & thought, the concept is great, but in a high pressure system the need to be certain that there are no air/gases present in the supply side seemed even more critical, yet no solution was in place. Positive displacement pump advantages aside (myth or not), I opted to install the Air Dog Fuel Preporator as this seemed to address a few of my concerns with this issue at one time - a real water separator (ie-greater than thimble volume), additional filter for increased filtration, generation of a positive system supply pressure, removal of entrained gases, & a low pressure indicator lite. I know-I know, I've seen the posts here, it's costly ($700 is expensive insurance for a $45,000 vehicle? how many folks spend more replacing a perfectly good stereo?). But so far, I haven't been disappointed. It seems to do what it claims. The truck runs better (not 100+ hp increase, it just seems to run better-smoother-quieter), fuel is more finely filtered, I'll know if the fuel supply pressure is low (a prime culprit of cavitation), entrained gases (another cavitation aid) are claimed to be removed (I don't have a lab to check that out but it does seem to run smoother so I'll just take their word for it), & I have some general peace of mind about it (& that is priceless).

If heat was the problem then everyone running around below 1/4 tank of fuel would have blown up by now due to the extra high heat generated by low fuel cycles.

Well that's my opinion and I am sticking to it LOL

Cooler and slightly pressurised fuel within reason is much better for the system as the fuel is used to cool electronics and injectors. Hot fuel combined with vac as seen with our system is a prime contributer to vapor release (Free vapors) and reduced cooling of the injectors. Not so much delayed fuel timing in a HPCR fuel system as everything should be returned to liquid post injection pump.

Thats another reason I like the fuel filter mounted post OEM and under the air box. Air from around the headlight acts as an effective fuel aftercooler (last in line before injection pump)while traveling. If anyone is in disbelief just hold your hand on the OEM filter after the fuel has had a chance to heat up, pass over the engine, then cool the EDU electronics. Not to mention being mounted to a hot engine. What I find is that my fuel in the OEM filter is hot and the post OEM filter mounted under the air box is cool. (Big difference) I would not hesitate to say + - 40 degrees. Cooler fuel going to the pump/injectors not only helps to keep them and other componets cool but is also helps to combat flashing of vapors and lubricates better. Many articles state that hot fuel lubricates less due to thinness and attracts more condensation due to the heating and cooling cycles. But thats another topic.