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Injector Nozzles

Has anybody checked to see how the increase in pop pressure affects the actual injected amount of fuel? Just a thought, but I know on common rail as pressure goes up you also lose more fuel to the return side.
 
That's the consensus, the higher pop pressure reduces fuel. All I know is when I changed out my n/a injectors for 2500 psi injectors, I had to turn the fuel down.
 
THEFERMANATOR said:
Has anybody checked to see how the increase in pop pressure affects the actual injected amount of fuel? Just a thought, but I know on common rail as pressure goes up you also lose more fuel to the return side.
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It certainly increases the amount of bleed past the pintle guide, but its miniscule in terms of injection volume, that I would say it makes very little difference in power.

Im not sure about your guys Bosch type injectors, but our Stanadyne type injectors have more than enough nozzle area (Equivalent of a 5x.019 DI injector)... We don't have the restriction in the tip like a DI engine has, so the injectors themselves are simply tuning devices.

Higher Pop pressure makes for a shorter injection duration, and more powerful event, and that's why you achieve a cleaner burn.

My G-code stanadynes in my truck have a .050" stroke increase, and I set them to 2500#. They are perfectly tuned for my 190cc of fuel. Just driving around, my truck is dead clean, and power feels great, and that's off boost with a laggy'er than normal S366 turbo.
 
I think you stated the main point succinctly. The stroke, pressure and fuel need to be tuned together. Stanadyne has it set up right for the hp they make stock. They also have to consider service life and other things like EPA regs, mileage....
 
Exactly,

Stock injectors are set to a pop pressure that delivers the stock quantity of fuel in the duration deemed to have the most efficient burn.

If you increase pop pressure without increasing fuel, your injection duration will be too little, and you will be wasting a lot of heat energy by burning all the fuel too early. That's not nearly an issue as having too little pop and burning it all out of the exhaust, which actually can help if you have a larger turbo.

Its all push and pull based on how you want your truck to react, what sort of mods you have, and biggest of all, how much fuel your running.
 
If the pump fueling is stock, I don't see any reason to bump pop pressure. The only reason would be to be able to retard timing a bit so you can reduce a bit of drag on the engine, but I haven't done enough testing with a stock pump to know if it warrants it or not.
 
RacinNdrummin said:
If the pump fueling is stock, I don't see any reason to bump pop pressure. The only reason would be to be able to retard timing a bit so you can reduce a bit of drag on the engine, but I haven't done enough testing with a stock pump to know if it warrants it or not.
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I raised it due to burning waste oils and testing with turbo 304 nozzles, they really seemed to sing nicely as the pop pressure went up.
 
We rebuilt our injectors in one of the fleets I worked at, so we played with levels a bit. Ip were always stock except db2 usually got 1/4-1/2 turn.

We found balancing them was the most crucial, but 2400 was where we set them all at for power/mpg. We also swapped exhaust out to 4". Other than experimenting with extra cooling its all we did. Stock turbos. Most trucks were WAY abused.
 
By All means, if more pop pressure makes your vehicle run better, its absolutely worth it.

That's really what it comes down to, tuning. The only thing to watch out for, is even though something might feel better, the dyno could read something totally different.

Bottom line is that if it feel better, then chances are, it is.

Ive been wanting to do an injector test on the dyno, just to see what it does to things, I just gotta get on the dyno.
 
Will L. said:
We rebuilt our injectors in one of the fleets I worked at, so we played with levels a bit. Ip were always stock except db2 usually got 1/4-1/2 turn.

We found balancing them was the most crucial, but 2400 was where we set them all at for power/mpg. We also swapped exhaust out to 4". Other than experimenting with extra cooling its all we did. Stock turbos. Most trucks were WAY abused.
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Matched injectors are great, its amazing how smooth these engines run when the sticks are within 50lbs.

The other thing to look at as far as you DD guys pop pressures/injection duration goes, is you have a shorter stroke, so reducing injector duration helps apply more combustion pressure in the proper crank angle.... Result is more torque. Our IH stuff has nearly 3/8" more stroke, that means more time to ignite the fuel over the proper crank angle, and better with a little less pop pressure...
 
Great info. Mine are set at 2500 and seem to work great, way better running compared to stock 1800 injectors and don't plug up as fast.
 
I don't know how to edit, I said 1/4-1/2 turn, it was 1/8 to 1/4 turn.

Something I didn't mention was it extended out oil changes. Maybe less volume of fuel caused less fuel intrusion? Idk and can't remember the dropped numbers allowing us to extend it.
 
Will L. said:
I don't know how to edit, I said 1/4-1/2 turn, it was 1/8 to 1/4 turn.

Something I didn't mention was it extended out oil changes. Maybe less volume of fuel caused less fuel intrusion? Idk and can't remember the dropped numbers allowing us to extend it.
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you only have a 15 minute window to edit a post.
 
I'm running 2300 and near stock tuning (mpg/tow w/ gm4) and I gained 1.5mpg on rebuilt squirters. I also did a vin F/egr delete so there are a couple factors to consider but I think cruising it helped alot.
 
iirc the ones it helped the most with mileage were trucks with more highway miles. If I can ever get to my Hummer again, that is on my short list and I'll see if it helps that.
 
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