3350 psi injectors?

[btoscano]

I just talked to the local diesel shop and they said for my truck they shim the injectors to 3350 psi. Is this right? I thought 3625 psi was the target pressure? Does 3350 cross reference to another year/model?



-brian

 

[BushWakr - RIP]

Brian, 3350psi is a bit low as far a popoff pressure. The stock injector on our trucks has a popoff of 245 bar (3601psi). From that point the upgrade injectors all have a higher popoff pressure.

Regardless of which injector is installed in the truck I'd still have them set to no less than that stock setting.

The higher the popoff the more you'll need to tweak your timing... . not huge, just a tad because it takes a few milliseconds longer to charge the line/injector to popoff point.

I'd personally prefer to have stock nozzles set to 255-260 bar. This will give a clean crisp spray pattern without overworking the pump.

BTW, Bosch will "accept" a range of pressure as "acceptable... I understand that they consider a spread of 8 bar between the high/low popoff on a set of injectors as normal.



pb... ... .

 

[bgilbert]

Bob, what pressure would you suggest having a HOT set of EDM's set to? I sure don't want to overwork the pump if not necessary.

 

[BushWakr - RIP]

Bill the first thing I'd do is talk to the supplier on that one... . I'm not avoiding the question here, just that they likely have taken that into account when the nozzle was designed... .

Having said that I'd look at a pressure setting of 260-265 bar. In my case for example the POD's I had reset were set to 275 bar. That was a bit high I think... . because there was a very distinct change in sound from the VE... it really sounded metallic and almost rattly. It was clear the old girl was working very hard...

As a result, I'd aim for about 260 to 265 bar as a MAX for the VE's benefit. I'd also suggest that with this setting you might want to use 17*advance as a starting point to begin your timing adjustments as well... the best results will be determined on a dyno of course but it seems that 17* is right in the range that most guys have good results with in terms of smoke/performance etc... .



pb.....

 

[btoscano]

I didn't think their number was right, thanks for confirming.



-brian

 

[btoscano]

Bushy,



If I'm getting late turbo boost (a very noticably surge at that) should I be focusing on getting the injectors reshimmed to lower their pop pressure, or turning up the pump some? The second disesel shop I talked to seemed more inclined to think the pump is set on the low side of fueling, and that is really where I should be focusing my attention.



-brian

 

[BushWakr - RIP]

I'm too sure what you mean by "late boost" to be honest... . boost comes from fuel and air burning... . what you seem to be describing is turbo lag... that's something we all struggle with in one way or another...

The smoke screw for example will have an impact on the very initial turbo spooling... but only the very initial onset...

In most cases you'll adjust your timing, starwheel and smoke screw... at least that's the primary ones for now...

The timing will have an impact on how touchy the throttle is for any given amount of fuel going into the engine.

If you have a tiny exhuast housing on the turbo it will spool quicker than one with a larger housing,... kinda the 12cm vs the 18. 5cm arguement sorta thing... for the very same amount of fuel.

You are basically correct about adding fuel to impact your turbo lag/no lag situation. .

You should be seeing boost develping at roughly 1500-1600 RPM or so (with some very slight loading)... not much later than that or you'll have more smoke and haze till it gets up and rolling...

The VE (without using any AFC fueling) will provide enough fuel to spool up a hybrid 35/16 in very quick order as is the case in my truck for example.



Try some tinkering with your timing to start with... make sure that right from the start you have an engine at operational temps so when you tweak the timing you don't get any false results as the temps increase on a cold engine would do...

While you're at it, keep an eye on the tach... you'll want to know if you are getting improvement of or not. .

Next would be to ease down the starwheel a bit and go again keeping the same things in mind. .

Remember, you WILL get to a point were you'll have smoke earlier and longer as increase the low boost fueling. . that's the job of the starwheel in the first place... it determines the amount of fueling rate increase per pound of boost so in effect what you'll be doing is raising the that rate till you start to see the exhuast snap that turbo into spoolup quicker... oh... and have fun... ya can't take it with ya. .



pb... .



ps: there are guys out there who know so much more about these things it should almost be illegal for me to give advice... ... well ok, prohibited were applicable. .

 

[btoscano]

Late boost is when the timing is advanced enough to get 16 MPG and a better top end. It seems to all of a sudden, and stay there. It makes low RPM sluggish and high RPM better. It means when I shift gears it doesn't feel linear. If I am accelerating onto the freeway, 3rd gear max at 50 MPH, shift into 4th, I don't get boost until later on. If I retard the timing down, the curve seems much smoother ... but MPG and top end suffers.



How did it come from the factory?





-brian

 

[bgilbert]

Your truck came at 12* from the factory.

 

[btoscano]

Bill,



Thanks... but I was referring to how did the boost at low/high RPM's from the factory?



From what I'm hearing, I should leave the injectors alone and turn up the pump to match them?



Brian

 

[JLEONARD]

I think these are all lag pigs at factory settings with factory turbos.

Mine had a feeling of being launched when the boost finally kicked in... about 1800 rpm maybe. . I sort of forgot.

With the smaller housing and the "other " adjustments, the power comes on smoothly.

Is that what you mean??

 

[btoscano]

yeah... and I like your analog... mine is the same way... . the Bosch tech recommended the smaller housing as well.



-brian