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Injector Nozzles

I wish I woulda adjusted my injectors when the heads were out!! I personally don't think your hot start issue is due to the high pop pressure. Next time you go to start it hot pour some cold water over the pump and see if it helps.

I'll have make myself a custom wrench to remove the injectors on the turbo side :mad2:
 
cub124 said:
I wish I woulda adjusted my injectors when the heads were out!! I personally don't think your hot start issue is due to the high pop pressure. Next time you go to start it hot pour some cold water over the pump and see if it helps.

I'll have make myself a custom wrench to remove the injectors on the turbo side :mad2:
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Appropriate smiley has been used! I've felt that way alot when under the hood of my truck.

I'll hafta try the water trick. Nothin to lose by tryin!
 
you got it! Youre also the lucky one, 6.5 heads have a better injector angle to remove them with the manifolds on, mine nearly rub lol
 
Cumminsfever said:
Sadly, I don't remember what my pump is. All I know it has small plungers.

What has me a bit puzzled is how it is actually injecting fuel (if it is a worn pump), because after it starts, it puts out a HUGE cloud of smoke. Ehh... it runs, gets consistant 18mpg, and easily runs away from a stock '02 powerstroke.
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is the smoke black, or grayish-white? with our pump mods, on start-up, we get a good cloud or dark grey-blackish smoke for the first minute or so, then it clears.... never had a problem yet with the coked up injectors, and we have close to 30,000 miles.... we mix with what ever we can find, went through 100 gals. of paint shop thinner (used multi-colored), and this winter we are running cut with gas and diesel, but one of our construction buddies just got us a 200 gal. tank of heating oil... so you guys know what we are burning the WMO mixed with this spring...LOL....:D
 
6.2 turbo said:
Mercedes sets them to 135 bar,which I think is 1950 psi. I still didn't decide what psi to set them too. I might be able to get a little more fuel from the fairly stock ip at a low pop psi. GM went from 1600 psi na to 1950 psi turbo. So if I'm running 40 psi boost I should have 3200 psi injectors ?
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Exactly, this is important when considering the system as a whole. If you increase cylinder pressures you have to consider what the injector is trying to inject into. The stock injector pop pressure was for a turbo running about 10psi. That is because 10psi of boost when compressed to 21:1 can make 1800psi air your injecting into. So its not going to atomize that well if it only pops around 1900psi. My guess is this is the main reason GM upped it to 2100psi for turbo use. Now, push 20psi and the 2100psi pop is inadequate, which is why I recommend everyone set their pop to at least 2250psi (I think at least a few guys have done this). I had my marines set at 2350psi and all injectors will settle a little lower over time. Now if you want to run 30psi sustained with 20:1 CR, then your pop should really be increased to at least 2500psi.

To run 40psi boost, your cylinder air pressure at TDC could be 3500psi (considering static CR of 20:1). The dyanamic CR (from intake closing after BDC and blowby) is a little lower than the static CR, so pressure is somewhat lower than that. I would say you would want set it for 3000psi pop for 40psi of boost if maintaining 20:1 CR. Me personally, I would lower the CR to 18:1 if running more than 30psi of boost, because it will bring down the cylinder pressure during compression stroke significantly. With 18:1 CR and 40psi then can probably get away with 2700psi pop injectors.

The IP will still push through high cylinder pressure though, just likely cause more burnt and mucked up nozzles and what not, maybe cause leaking injector and scratch up cylinder walls and burn a hole in the piston. These IPs will push nearly 10,000psi at full output at high RPMs. The pop only starts the injection, and it goes higher during the event. Definately dont want to lower the pop pressure.

Cumminsfever said:
Starts better than ANY other 6.5 I ever saw. Hot or cold. Has a rattle similar to a cummins. A beautiful sound!
My next set is set at 3200. Going for max atomization. My experience has been- less smoke, more power, and obvious fuel mileage improvement. This is a db2 with the screw turned in, on a 94, with a gm8. Otherwise it is stock.
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6.2Turbo can comment here, because I think in the past he said the DB2 would lock up between 4000 and 5000psi at idle RPMs. If thats true then cranking RPM wont be able to push much over 3000psi, could be struggling to do that. Testing that limit would be a good experiment. It may cause a little more wear and tear constantly having to push to 3000+ psi at crank and idle, when in normal idle injection it may only hit 2500psi. Being able to get those type of readings pressure readings would be awesome to make some judgment on durability impact. I dont suspect that there is any negative impact just up to 2500psi or so.

Its that injector noise and clatter that a lot of people dont really want, and its already a noticeable difference just going up a couple hundred psi. I am really encouraged to see it working at 3000psi pop, but have you compared to 2500psi or 2700psi, ect... anything over stock 2100-2200psi?

I was in contact with Monark (A US sales rep and their direct production manager) for about 6 months (this was over a year ago) about making nozzles for our injectors. The US sales rep even claimed they had made them once in the past. I was considering buying 300 of them just to get it rolling (the lowest production order). However, eventually they just caved and said they were incapable of retooling to make them. That was a big disappointment, since as stated, the Bosch German nozzles are rare and all old stock.
 
turbonator said:
is the smoke black, or grayish-white? with our pump mods, on start-up, we get a good cloud or dark grey-blackish smoke for the first minute or so, then it clears.... never had a problem yet with the coked up injectors, and we have close to 30,000 miles.... we mix with what ever we can find, went through 100 gals. of paint shop thinner (used multi-colored), and this winter we are running cut with gas and diesel, but one of our construction buddies just got us a 200 gal. tank of heating oil... so you guys know what we are burning the WMO mixed with this spring...LOL....:D
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A couple of the things you guys are burning is what is keeping your tips clean.

The smoke after it starts is mostly gray/white, which I have learned is MAJOR unburnt fuel.
If it only cranked a few revolution, and then started, it puts out BLACK smoke.
 
Cumminsfever I think its time for a video so we can hear this injector/cummins noise lol. Im set on changing my PP (pop pressure) now but now that Buddy chimed in I can't decide what psi to go to, I was thinking 3,000 but maybe I'll just do 2,500.
 
cub124 said:
Cumminsfever I think its time for a video so we can hear this injector/cummins noise lol. Im set on changing my PP (pop pressure) now but now that Buddy chimed in I can't decide what psi to go to, I was thinking 3,000 but maybe I'll just do 2,500.
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I don't own a video camera, and cell phone footage isn't worth the space it takes up in my opinion.
I should just ride up the road and see you sometime.
 
I am guessing there is a sweet spot around 2700psi that would be the limit I would try until more data is available. 2700psi would still be better if only pushing a sustained 30psi with 20:1 CR, I just dont know what kind of extra noise that would be.

Some early 90s Cat pumps rated for 350 to 425hp were tested out to 2700psi. And then newer ones out to 3500psi. And then there are the Cummins VE pumps, a pump that looks more robust and outputs more that had the pops around 3500psi. One of the reasons they can run more boost.

That is really only a guesstimation from what research I could find on other early 90s pump designs, and 6.2Turbo's experience with idle pressure limits. Has Stanadyne continued improvements to DB2 internals as they have the DS4, with hardened, lower friction parts? Those improvements would help keep them alive. So there is some speculation there, but what is very true is that you really do need to increase pop pressure if running sustained higher cylinder pressures from high boost.

Higher pop pressure would also cause higher peak line pressures, because the fuel metering is done at the pump and number of degrees rotation. So the stoke of the plungers is the same before the metering valve stops the injection, the fuel is going to get squirted, but with higher pop pressure that duration is a little shorter, so to get all the same volume out in that same number of degrees of rotation it will be pushing harder. So some higher peak line pressures and injection pressures. Thats all a good benefit for atomization and combustion. However, we dont know how high you can go before affecting pump longevity. My point here is just that there could also be more wear at high fuel rates as well.
 
Buddy- I'm guessing you don't know that cummins, perkins, and yanmar also used a stanadyne pump, same as the 6.2, just not as many cylinders.

The cummins and perkins engines that I tested had pop pressures between 3300, and 3800. The yanmar I saw was on the job, so of course I didn't get pop pressures tested.
 
buddy said:
Thats good info, what are the pump models on the Cummins? Was that stock or what was the stock pop pressure for those?
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DB2xxxx xxxx pump, stock pressures.

Maybe you should check into stock pop pressures for a marine 6.5 set @ 275hp? Service manual states 3300psi if I recall correctly.
That is where I got my idea to go for 3300psi, as that must be where they designed the nozzel to work? What do I know. It works for me...
 
The only service bulletin I have seen for marine 6.5 injectors showed a pop pressure of 2200psi, like 150bar.

The real question is if there is a noticebale difference between say 2500psi and 3000psi for a person only running 20-25psi of boost. Any reason to push it and possibly shorten the life of your IP. And how can we characterize the difference in longevity.

I really couldn't find much about Cummins and DB2 pumps because they were from the 80s before internet and everyone likes to talk about and switch to the VE pumps.
 
buddy said:
The only service bulletin I have seen for marine 6.5 injectors showed a pop pressure of 2200psi, like 150bar.

The real question is if there is a noticebale difference between say 2500psi and 3000psi for a person only running 20-25psi of boost. Any reason to push it and possibly shorten the life of your IP. And how can we characterize the difference in longevity.

I really couldn't find much about Cummins and DB2 pumps because they were from the 80s before internet and everyone likes to talk about and switch to the VE pumps.
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I guess we'll find out on longevity. Pumps are cheap. Injectors are cheap. I have time to change out either.
 
buddy said:
Thats good info, what are the pump models on the Cummins? Was that stock or what was the stock pop pressure for those?
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the pumps would be numbered something like this i would imagine( i have down-loaded so much info for these pump numbers): cdbg-4431, or jdbg-2350, 0r 2437, maybe 2445.... also dont forget they were possibly roosa-master/CAV pumps.... the g would stand for generator, the c cummins, and the "j" for john deere.... we do know that the .450" plungers have been discontinued by stanadyne....
 
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