2L vs 2LT injector pop pressure (1 Viewer)

[4Ruster]

Hey. I have an early model 2L NA diesel. Factory spec states 2100-2260PSI. The injectors I bought I just tested at 1700 PSI. Just because, I swapped in my old springs and shims and upped them to 2000-2200PSI (didn’t have enough shims to get them all the same) to see what would happen. I was expecting better performance. Right away I noticed the truck actually seems slower, blows less black and EGTs are lower but I lost all of my steam going up hills. I tried advancing, the pump slightly but not much changed.

Im going back to the lower pressure this weekend, however I’m curious why the higher pop pressure seems to be worse for performance. The spray patterns were fine looking (before, two of the nozzles were actually spraying weird, so you’d think it would improve just because of the better pattern alone).

 

[KiwiDingo]

If you increase injector pop pressure without increasing pump fueling then of course the overall fuel delivered into the cylinder will be less. With no pump changes the injectors with the higher pop pressures open later and also close earlier compared to the injectors with lower pop pressure hence the reduction in fuel delivered.

 

[4Ruster]

If you increase injector pop pressure without increasing pump fueling then of course the overall fuel delivered into the cylinder will be less. With no pump changes the injectors with the higher pop pressures open later and also close earlier compared to the injectors with lower pop pressure hence the reduction in fuel delivered.

I did turn the pump up slightly though. It blows black and loses power way sooner now. Some hills I have to go 35km/h up now instead of accelerating up to 50.

 

[AussieHJCruza]

You've also effectively retarded the timing by increasing the pop pressure

 

[Dougal]

Some pumps are very sensitive to injector pop pressure and will deliver less fuel with higher pressures.
It's due to internal leakage (increases with higher pressures) and everything flexing so more stroke is taken up expanding lines etc.

You'll now have to turn up your pump to get the same fuel delivery you had with lower pop pressures.