injector pumps are they progressive

[jimraelee]

I got to wonder this weekend, when you crank up the IP does this increase the fuel delivery across the entire throttle range??? Or does it ack like a booster venturi on a carb, that only dumps extra fuel when certain amount of throttle depression, like the second half???

 

[david85]

Fuel flow and pressure goes up across the range. You will notice that even idle RPM is affected slightly.

 

[jimraelee]

well then this would help mileage. Im looking to increase my mileage, its getting low after turbo install 14-12mpg... kind of sad when all of you talk about 16-20mpg.

 

[Agnem]

Idle speed is controlled by the min/max govenor setting. Turning the fuel up shouldn't affect that.

 

[jimraelee]

well Mel, I'm more thinking of backing off the IP allen screw to cut down the fuel and get better mileage.

 

[Agnem]

That would have the same effect as not pushing your pedal down as far. Put a rock under your throttle pedal.

 

[jimraelee]

oh mel, your too funny

 

[4play]

backing off the screw will gain better economy, and also less overall power. keep in mind diesels run wide open all the time. you control fuel rate through the throttle. the screw controls "max" fuel rate. it does not control idle or and type of cruising speed/rpm... so basically the best way to gain economy without loosing power is to lighten up your right foot.

 

[smoking89IDI]

backing off the screw will gain better economy, and also less overall power. keep in mind diesels run wide open all the time. you control fuel rate through the throttle. the screw controls "max" fuel rate. it does not control idle or and type of cruising speed/rpm... so basically the best way to gain economy without loosing power is to lighten up your right foot.

Ditto, I cranked my fuel screw way up and am getting better mileage and more turbo boost a bit sooner but only if I don't hot rod it. You will hate it if you turn down the pump, it will be like there is no turbo at all, remember the turbo is spun by HOT exhaust gases and when you turn down the pump you turn down the heat giving the turbo LESS exhaust gas to work with and therefore less boost which means less power which means skinny peddle does more work and burns more fuel. Hope that made sense.

 

[david85]

Just going from personal experience, but every time I adjusted the fuel screw higher, the truck would start easier and idle slightly higher (50 - 100 RPM higher). As I understand it, the fuel screw not only adjusts flow, but also the size of the pressure spike that fires the injectors.