Hi,
what is exactly your plan? I mean what do you want to change? What does the pump voltage change?

br
Greg

Hi,
all pump driven injection systems do not have the possibility to change the fuel pressure. This means all distributor pumps and UNIT PUMP can not change the pressure. This can only be done with CR systems. You could change the force on the inner spring (for the main Injection) to increase the injection pressure for Main Injection.
What naturaly changes the fuel pressure inside the Nozzle Tip is the pump speed, with fixed ratio to the engine speed. In addition the Nozzle size has an impact on the opening behaviour of the Injector Needle. The reason for this is, that with higher flow rate (=Nozzle hole diameter or number of holes) the pressure decreases. In the end this is in opposite to what is required for the combustion in low engine speed and low load. Therefore the behavior of your engine is as expected (even if it is not nice:-))

Now comming to your soot problem. Talking about soot formation there are finally two factors which cause the soot formation.
1.) local Lambda
The local lambda is described by the area where the fuel droplets react with the oxygen in the combustion chamber. The bigger the droplet is the more soot is generated due to the reduced reaction speed and availability of reaction Partner (O2 and HC). Therefore the reaction is shifted in direction CO and C (which is pure) soot.
2.) global lambda
This is the over all lambda calculated from fuel and air. The mechanism is comparable, like the local lambda, but here it is the pure amount of available oxygen for the reaction and less the reaction on thr droplrt surface.

Now coming to your problem.
I Think it will not be possible to change the local lambda due to the fact that the fuel pressure can not be changed (except for the spring force as explained above). What you can try is to change the SOI (start of injection) to increase the amount of homogenious mixture between air and fuel before (self)ignition. But I think the impact on soot creation is quite small.

Another thing is the global lambda. This can be influenced more easily. To increase the amount of oxygen it makes sence to decrease the amount of EGR, so to increase the desired air mass flow in the Table for M_air_Desired.
This of course only works in the area where the EGR is active. In addition you could increase the boost pressure, but this only works in higher part load and of course only if you have the VNT turbo charger.

Didi you try to change EGR rate already?
By the way, if you realize an increased combustion knock, this is quite norman, increaed EGR rate decreases the combustion speed and therefore the pressure rise / deg CA.

I would be interested about the outcome of your investigation.

BR
greg

I think he wants to say that he fitted bigger nozzles, so the pump linearization to reach a certain IQ is no longer correct.

Although the nozzles don't determine the amount of fuel, just how it is injected.