Nozzle opening pressure

[Leiffi]

I have been told that opening pressure should be higher when larger orifices are used. Is there any rule of thumb how much it should be raised from stock if nozzle flow is increased x-amount ?

 

[Big Blue24]

Lots of mild 5x.014" and smaller 12 valve aftermarket injectors in the 260-285 bar range. Lots of competition 5x.018"+ 12 valve injectors in the 240-330 bar range with most I've seen in the 290 to 315 area.

Maximum flow occurs at lower opening pressure, optimum fuel delivery occurs at higher pressure generally speaking.

 

[Leiffi]

I have a unit pump engine, stock nozzle is 6x0.27 and opening pressure about 300bar, dont remember exactly. I change to +30% nozzles, how high they should be adjusted ? I know some has used up to 400bar but it sounds quite high to me, might have some negative effects like needle wear.

 

[No Sparkplugs]

Wow. 400bar? I was going to post our experiences but the I realized that in the grand scheme of things. 285bar is nothing.

 

[HeTheAethyr!]

there's probably a curve somewhere showing fuel ramp rate and opening pressure.

I would say its a safe bet to assume its to help with atomization.

400bar is damn high but don't keep up on 12v stuff

 

[Leiffi]

there's probably a curve somewhere showing fuel ramp rate and opening pressure.

I would say its a safe bet to assume its to help with atomization.

400bar is damn high but don't keep up on 12v stuff

It's about cylinder pressure trying to push the needle open before injection or prevent closing it after injection. The larger the orifices the higher the force effecting needle but the question is how much higher ?

I think I try max 350 bar, should be enough.

 

[HeTheAethyr!]

cylinder pressure? then common rail injectors are way under sprung.. the injector mechanically start operating at 100bar for off the shelf injectors and people have been swapping BIG hole nozzles for years with.

 

[Leiffi]

cylinder pressure? then common rail injectors are way under sprung.. the injector mechanically start operating at 100bar for off the shelf injectors and people have been swapping BIG hole nozzles for years with.

railpressure keeps commonrail nozzles closed, they are a totally different design.

Then there's Cummins PT, Celect and HPI that have no needle at all.

 

[murphy41]

It's about cylinder pressure trying to push the needle open before injection or prevent closing it after injection. The larger the orifices the higher the force effecting needle but the question is how much higher ?

I think I try max 350 bar, should be enough.

What kind of compression, RPM, Cam and turbos are you running that this is a concern ? I mean a .029 hole is no doubt large, but I didn't think that this would be a concern set at anything over 290ish bar ? Considering even high compression motors don't produce anything close to 290bar worth of cylinder pressure to have a reverse effect on a pintle. Theoretically thinking anyway. I'm not nay-saying your theory cause I don't know enough about it. I'm just asking questions to go along with it. Another question is, how much timing do you plan to run if the injector is set to 350bar like your talking ? Then what size lines, pump are you using that'll affect line fill time and timing as well?

 

[HeTheAethyr!]

railpressure keeps commonrail nozzles closed, they are a totally different design.

Then there's Cummins PT, Celect and HPI that have no needle at all.

equlized pressure on top and bottem of the needleallow the 100 bar spring to keep the needle seated. the solenoid lifts the ball bearing creating the pressure difference starting injection.

PT, the IFSM HPI used barrles, plungers, cups same ****

 

[Leiffi]

equlized pressure on top and bottem of the needleallow the 100 bar spring to keep the needle seated. the solenoid lifts the ball bearing creating the pressure difference starting injection.

Unit injectors have fuelpressure only on one side, when the plunger starts to come down and spillport is closed, pressure starts to open the needle and it opens earlier (and closes later) the more the cylinder pressure is helping it, thats why opening pressure is raised when nozzles are bigger. The question is how much ?

 

[Leiffi]

What kind of compression, RPM, Cam and turbos are you running that this is a concern ? I mean a .029 hole is no doubt large, but I didn't think that this would be a concern set at anything over 290ish bar ? Considering even high compression motors don't produce anything close to 290bar worth of cylinder pressure to have a reverse effect on a pintle. Theoretically thinking anyway. I'm not nay-saying your theory cause I don't know enough about it. I'm just asking questions to go along with it. Another question is, how much timing do you plan to run if the injector is set to 350bar like your talking ? Then what size lines, pump are you using that'll affect line fill time and timing as well?

16.1 liter in-line 6, 4 valve heads, 18:1 compression, Delphi E1 injectors, Garrett GT50 82/118 99/91 1.23 A/R. Starts to spool at 1000 rpm, maxed out at about 2200 rpm, rpms stretched to 2900 but fueling limited to keep the turbo from overspeeding. I'll try about 4 degrees timing advance through the rpm range in the beginning, then finetuning from there.

It's a working truck hauling loads everyday but might do some sledpulling in stock class and some 1/4 mile passes. Must pass smoke test and I don't want it to smoke anyway.

 

[murphy41]

It is all starting to make sense now. Cummins, Detroit ? haha That is an awfully large displacement. Definitely not a C-16 cause they are 15.8L Curious on what it is now.

 

[Leiffi]

It is all starting to make sense now. Cummins, Detroit ? haha That is an awfully large displacement. Definitely not a C-16 cause they are 15.8L Curious on what it is now.

Volvo D16 610 hp Euro 3 emission

 

[Leiffi]

They were set at stock Penta opening pressure of 325 bar. No haze, no rattle, idling like stock. Attached injector test report.