dv's impact on injectors and pop pressure adjustment

[BradenAnders]

So I have read a lot of threads about delivery valves and I still have a couple questions because my 95 auto 160 pump is acting a little strange after machining down my stock 131 dv's to a 191. My egt's did not get that high so I wanted to ad some more fuel.

1. How do dv's affect injectors besides just feeding more fuel

2. How does injector pop pressure affect dv's and if I reset them what would be good?

3. I have read a few places that said dv's plunger depths can advance or retard timing. Any thoughts?

 

[JariV]

1. In my understanding a delivery valve fills up the fuel line to the injector and therefore with a longer duration delivery the fuelspray fom nozzle will also be longer.

2. Pop press dictates when the feed line open and closes. Lower pop press will add duration. This is however a combination with pressure that is needed to atomize the fuel. So atomization goes bad with lower pressures.

3. the lower you install the dv holder the more duration you get. The original 160hp pumps have shims under the 131 holders which are to reduce dv duration and once you take them out you will have more duration.

These are only my thoughts, nothing more. This is how I have understood these things. I might be wrong.

 

[BradenAnders]

I took out the thin washers to see if would run any smoother but I didn't really notice a difference. I wonder why they stopped using the washers after 95. I want to try some 215 injectors and see how it runs

 

[Chevycummins]

pop off pressure is good to a certian extent you get too high and it causes the pump to work too hard and it will wear out faster. if its too low then you lose atomization. when i went from about 200 bar to about 290 bar and noticed a cleaner burn on full acceleration and also a better throttle response.

pop off pressure and dvs will effect timing a little bit by maybe a couple degrees at most. i gained a little bit of hp by upping my pop off and havent been able to drive it long enough to test to see if my mpg increased but i would assume that with better throttle response and cleaner burn that it would go up some. i think most try to shoot for 270-300 bar for pop off pressure.

as far as dvs i went from a 131 to a 121 which the only difference i noticed was the taper on the dv its self and it appeared to run smoother also didnt add a huge number of power but helped a little.

i doubt that the pop off will effect the dvs i believe its the other way around, if the dv doesnt let enough fuel around to build up enough pressure to open the injector then it wont run right.

also the length of the dv doesnt change timing its the shoulder of the dv the less shoulder you have the longer duration that its open to let fuel through.

it wouldnt hurt to pull your injectors and see what the pop off is set at. not sure why it would run a little funny after altering the dvs unless there is a bur on them and its sticking a little bit. for sure depending on the age of the injectors or miles i would check pop off pressure. imo i would set it up between 280-290 bar, that seems to be a good area to start with what you got going there.