rebuild injectors/bad spray pattern

[Toby]

EGTs get high for a number of reasons, not the least of which is unburned/still burning fuel getting dumped into the manifold(s), which is why we universally see higher EGTs with more fuel. As the mixture goes up so do the CC temps UNTIL there is more fuel than can be burned, at which time CC temps decrease due to incomplete combustion and evaporative cooling of the unburned fuel. A stream of fuel does not burn nearly as hot as a well atomized one. I am not saying single cylinder overtemps and attendant damage due not occur, merely that a poor spray pattern is not the cause.

I have seen lots of cars with pissing injectors and NO cutting torch action. It should be noted that diesels that get melted down always have pissing injectors, so I suspect that they are a symptom of a meltdown, not the cause.

[fatmobile]

My mechanic had some info from bosch,
 shiney posters with pics of glow plugs in different states,
one burnt off,.. and a list of possible reasons included bad injectors.
 I've seen an '85 Jetta TD with no either can and 4 burnt-off injectors.

I've seen an engine that I know the owner used either on,.. and the glow plugs didn't work,.. but weren't burnt and the engine runs great.
He swore the trick was to just use a very small squirt.

[Toby]

Cool, so if someone has dangerously high EGTs, they can save their engine from meltdown by just turning their fuel up more and getting that evaporative cooling effect.  I never knew that before.  On a similar note, I've also heard that you can port and polish your engine by pouring sand in the intake while it's running.

The EGTs won't go down by adding more fuel because that excess fuel is burning in the manifolds. The CC temps are lower  when vastly overfueled because combustion is incomplete. When compared to when it is properly fueled.

If these engines are significantly over-fueled they don't run cooler, they melt with the piston crown flowing down past the rings in a most disturbing way.  Complete engine meltdown happens before a stoich mixture is achieved. 

I am not saying that motors don't melt down. Just that a pissing injector is not the cause.

Not too many years ago it was typical to see semis out on the great plains running what they called the "intermountain pump" trailing huge amounts of black smoke as they went by at 90+ and when climbing the foothills of the Rockies. At night you could see flames licking out of the exhaust stacks. Hence the words to the truckers song "13 days". "My rigs a little old, but that don't means she's slow, I got fire out the stacks and she's blowing black as coal"

Clearly these trucks were running way past stoich and did not melt down, so a pissing injector in a Rabbit diesel isn't going to do it. I suspect that what does it is too much fuel AND too much timing. It has been known for decades that max power comes with excess fuel and LATE timing. Talk to the guys building the 1200 hp big cam Cummins motors that they run in the semis and the guys racing the semis on circle tracks, or the Les Schwab semi stunt team.

I suspect that the max hp diesels are not very snappy, if my experience with automotive diesels is any indication. I for one would be happy to give up some top end hp for much better mid range performance. 100 mph in a N/A Rabbit diesel is all that I need. The best thing about my 5000TD is the oustanding mid range torque. That comes from lot of timing in early. It does, I suspect, limit how much fuel I can put into it. I would not trade any of that for another 20 mph on the top end.

[theman53]

Toby since injectors for you are not a maintenance item...
When I need new injectors then can you buy some and send them to me. I'll send you my old ones for the new ones. I will pay shipping both ways of course.

[Toby]

Toby since injectors for you are not a maintenance item...
When I need new injectors then can you buy some and send them to me. I'll send you my old ones for the new ones. I will pay shipping both ways of course.

I never said that injectors are not maintenance items. Far from it. I haven't owned an injector tester for 25 years, nor have I changed hundreds of nozzles because I think it is not important. I am just trying to dispel some magical thinking ans mountain medicine. Perhaps if you guys have some Bosch info indicating that I am wrong you could scan and post it or point me to a Bosch site that backs up what you are saying. I suspect that it is a myth retold so many times that it is taken for the truth without question.

[Toby]

FWIW, if the excess fuel is burning in the manifolds, then you are still not above stoich. 

Stoich does not mean that no oxygen remains in the exhaust. It means that the ratio of fuel to air allows for complete combustion of the fuel w/o excess air. When the mixture gets above stoich combustion is not as complete as it is below (in a diesel) and excess fuel and unconsumed oxygen both end up going out the stack.

Pardon me if I trust Bosch and the experiences of others who have had it happen to them more than I trust you about this.     I'm done with this discussion.  I hope you don't mislead too many people.

As I said before, point me to some Bosch literature that tells me that I am wrong and then I will believe the conventional wisdom. So far 25 years worth of experience does not support your contention. So educate me.

[theman53]

Toby since injectors for you are not a maintenance item...
When I need new injectors then can you buy some and send them to me. I'll send you my old ones for the new ones. I will pay shipping both ways of course.

I never said that injectors are not maintenance items. Far from it. I haven't owned an injector tester for 25 years, nor have I changed hundreds of nozzles because I think it is not important. I am just trying to dispel some magical thinking ans mountain medicine. Perhaps if you guys have some Bosch info indicating that I am wrong you could scan and post it or point me to a Bosch site that backs up what you are saying. I suspect that it is a myth retold so many times that it is taken for the truth without question.

If bad spray/worn nozzles aren't maintenance on an injector the only other thing could be breaking pressure, right? Offer is still on the table, I send you my old ones and all you will have to do is make sure the opening is correct. I will take the new with shipping of course.

[R.O.R-2.0]

fire is hot. it melts pistons, and glow plugs.. and a stream of diesel makes a pretty skinny, hot fire..

[Toby]

You are forgetting a number of things:
1) Un or poorly atomized fuel does not burn well nor very hot. (read that "pissing injectors")
2) In an IDI diesel the injector stream first hits the wall of the precombustion chamber, swirls around, burning as an overly rich mixture and then exits the PC chamber to complete its burn in the main CC. Nowhere does a stream of fuel ever hit the piston.
3) The glow plug is not in the center of the injector spray pattern. The stream needs to be off center a bit to hit the glow plug and most pissing injectors that I have seen shoot pretty much straight. Not all, but almost all that I have seen. Ether on the other hand will take the end off of a glow plug in a heart beat  if it gets into the PC chamber, as will being a bit too heavy on your glow plug switch or an erratic glow plug controller.

Also please note that I am not saying that a bad spray pattern won't damage your engine. Just that it won't create a cutting torch effect. It will wash down the cylinder walls and dilute your lube oil as well as carbon up the inside of the engine.

[blackbird82]

Toby, you are so close to truly understanding diesels
yet you cling to ideals that are based in the gasser world
first off "Stoich"
haha, a diesel NEVER runs Stoich.  It may briefly touch it for a second, but moves around it like a dancer on the floor

and yes streams burn holes man.  This ain't no Chevette, when fuel goes in to that pressure it does burn and streams, burn late and hot! 

On direct injection Deere's if you got a straight shot out a bad injector (piss line)
10 times out of 10, you got a hole right below it in the piston.  Ask me how I know (JD Master Tech)
And the reason the sled draggers inject late is the amount that they do inject,  later in the injection delivery the more heat in the cylinder (DIRECT INJECTION ONLY) and they need all the heat to light the pail of fuel they throw in.  In fact, you gotta disregard everything about those guys.  Tuning a street diesel like they do is like runnin NITRO METHANE in your I'm assuming CHevy MAlibu.

Don't piss off these guys, the collection of knowledge on this site is astounding, and no one wants your piss in this pool

[R.O.R-2.0]

loooool...

so many people assume gassers and diesels operate under the same principals.. but not even close..

diesels are a different breed. the only thing they share with a gasser, is the fact that they are a piston engine, but other than that, not much in common..

"no one wants your piss in this pool"

that was awesome, i must say..

im going to remember that quote for sure..

[smutts]

THREADJACK AHEAD!
Anyone remember that swimming pool scene in  Caddyshack?
END OF THREADJACK............

[blackbird82]

Screw Caddyshack

Best old school movie was 'The Great Outdoors'

With my favortie dude John Candy, another great Canadian!