Diesel Injector Pressure 1

[billyonemate]

Hi,

I have an Italian WM 2.5 ltr diesel engine in my 1999 Jeep Cherokee.

http://www.vmmotori.it/

I want to up the injector pressure by 20 bar for better atomization of the fuel, but the new injectors I have bought have different pressure.
The #1 injector (which has a needle motion sensor in it and controles the timiing) has a pressure of 165 bar, and the other three have a pressure of 150 bar.
Two questions:
1. Is it normal to have the #1 injector have slighty higher pressure than the others.
2. If i do up the injector pressure by 20 bar, do i up all four injectors to 170 bar, or do i up #1 injector to 185 bar, and the others to 170 bar?

Any thouhgts help greatly apprecciated.

Thanks

 

[TheRookster]

Your injectors should all have the same pressure at opening.

Upping the pressure won't help, most injection will actually be at greater than 600bar upto about 1200 bar, the injector pressure is just set for initial opening.

Simon

 

[kenre]

If you up the injection pressure you will risk having the fuel inject straight through the air and onto the cylinder walls or piston where it will do no good at all.

Ken

 

[kopron]

We tested diferent pressures on our diesels, and currently my cousin is driving WM Cherokee 2,4 L at 173 bars with no problems . We yust had 2 add a little degrees of pre-timing of injection on fuel pump. I personally went to 235 bars on my VW . I got more torque, power and smaller fuel consumption for 25-33 % + lower exhaust smoke. But all that achieving was 4 the cost of noise, that gets annoying at higher pressures. That's why we stayed at 170 bars , and the same reason also other factoryes didn't go higher than 158 bars. Better is TDI with 2 stage mechanical injections . Sorry 4 my bad language, in Slovenia we don't speak much english ...

 

[billyonemate]

In the end I got all my new injectors upped to 170 bar, and got them fitted by Jeep today (Jeep had to fit them because in my 1999 model you have to re-programme the MSA computer to expect a new injector, apparently.)
All the injectors that where took out where 150 bar, so why the new number one injector i got was 165 bar i do not know.

I took it for a 20 mile test drive and all appears to be running fine, there is no loss of power or excessive smoke out the exhaust.
I think what happens is when you re-programme the MSA to expect a new injector, it detects the pop-off pressure of the new injector, and sets the timing and pressure on the injection pump accordingly, so there is no need to manually adjust the timing on the fuel pump.

Hopefully the fuel is atomizing better now and I will get better torque and better emissions.

 

[kopron]

No, i think that your car yet does not have automatic regulation of timing at 1999 year . But i can sure you, that you got less smoke from exhaust, but torque is achieved by adding more pre-timing. Anyway, stay at this point 4 a while and continue latter ...

 

[billyonemate]

Kopron, Below is what the Manufacturer's manul says about the fuel pump, so i guess it does have the automatic regulation of timing.
----------------------------------------------------
In the elctronically controlled injection pump, the pump plunger works the same as the pump plunger
in the mechanically controlled injection pump, but the amount of fuel, and the time the fuel is
injected is controlled by the vehicle's MSA, instead of by a mechanical govenor assembly.
A solenoid controlled by the MSA is used in place of Mechanical Govenor assembly, and it moves a
control sleeve inside the pump, and regulates the amount of fuel that is being injected.
---------------------------------------------------

 

[kopron]

I know the principes of working, yust that i didn't know the right type of the motor/vehicle . But if you write as you read, than it should be so . So thank you for the informations anyway .

 

[billyonemate]

yes, Thanks for all your help kopron, the engine is now running sweet with all injectors at 170 bar, even if it is a little noisier as you mentioned, but not too much.