Engine/Transmission (1994 - 1998) 12 Valve Injector Pop Off Pressures

[Cooker]

It appears that the 12 valve injectors should pop off at 260 bar, is this correct?



What would happen if the pop off pressure was lower than that equally across all six injectors? What if it was higher?



For overall driving would it be better to raise the pop-off pressure or lower it? What about in a performance application?



Thanks,

Ryan

 

[ndurbin]

I was told 250 bar when I rebuilt mine acouple years ago in school.



If they aren't set at the correct pressures, as I understand it, they well not inject the fuel in at the correct time. But changing pop-off pressures to inject earlier or later could be looked at in the same general idea of timing advance or retarding. It may not be as simple as that but to me you could play around with the pop-off pressures to see.



Nathan

 

[chrleb1]

You would not want to lower the pop-off pressure. This would retard the timing, and it also would not atomize the fuel as well. The more pressure you have, the better.

 

[Vaughn MacKenzie]

Going higher will likely add stress to the P7100 and the injectors. Probably best to stick with OEM settings.

 

[dpuckett]

There has been quite a bit of R&D going on among first Genners- the VE doesnt put out the pressure of the P7100, so higher power levels cant be attained as easily, without making clouds of smoke and/or high EGTs. SO, some guys have raised the pop pressure, to increase atomization and cut smoke. The POD injectors I believe are set to 260bar. The P7100 is known for its ruggedness and reliability; I dont think a few bar higher pop pressure would hurt anything. Some performance shops set it to flow more than 800mm/ stroke; talk about pressure!! You may have to advance your timing a degree or two, tops, if you go higher pop-off, as it has an overall effect of retarding the timing. The spring holds the pintle shut longer, thus injecting the fuel a split second later.



Daniel

 

[JoeBioDiesel]

If you want to fool around with crack pressures in order to gain performance, then adjust all of them to pop at the exact same pressure. That will make sure you don't have timing that varies from cylinder to cylinder. Raising the pressure does what Vaugn says, and lowering it reduces atomization, like chrleb says. Stick with the stock numbers.

My 2 cents.



Joe