Shimming the injectors...

[240ZD]

I know a diesel guru who shims the injector springs of his diesels to raise the pop pressure by a few hundred psi. He has done this to several vehicles, including a ford powerstroke and volkswagens, and I think GM diesels. Supposedly this yields an enormous increase in power (like 30%) by atomizing the fuel better. And I think higher mileage, too.

For the LD28 I've been "prescribed" an increase from about 2000 psi to 2400 psi, which would be done at an injector shop, of course. Even though such shops have been known to refuse to shim injectors without explanation.

After increasing the pop pressure, you end up having to advance the IP timing slightly to compensate for a miniscule lag or retardation in the fuel system.

I've been told that this will not increase wear and tear on the IP or cause fuel leaks. Yet somehow, for some mystic reason, I keep getting the feeling that I'm gonna blow my headgasket if I do this!

Maybe the New Zealanders and Aussies have tried it before.

[rlaggren]

Well, it certainly puts more pressure in the pump and injector lines. You might want to be sure and run an additive in the fuel to improve the ULSD lubrication properties. I have read here and other places that ULSD lubricates significantly less and that it _dose_ affect many engine (even w/out tuning). The Ford 6.9 is one of them and I can testify that mine doesn't like ULSD - it stalls out at stop lights if I don't put an additive in.

Rufus

[240ZD]

I also use additive with every fill-up. My engine runs noticeably better and even quieter with something extra in its ULSD, even plain ole' marvel mystery oil.

[Carimbo]

Supposedly this yields an enormous increase in power (like 30%) by atomizing the fuel better. And I think higher mileage, too.

30% seems a bit optimistic, but of course it depends on the current condition of the injectors. If they are in bad shape, clogged, stuck, dripping, non-uniform spray pattern, then cleaning and resetting them to just stock specs (supposed to be cleaned and serviced every 15,000 miles) will produce surprising results. IF they are currently in good condition, I doubt upping the popoff PSI that much will net 30% HP gain.

Also would depend on the engine design. Remember the LD28 injectors are 0 deg. spray pattern, spraying into a precombustion chamber-- doesn't this make it less receptive to injector changes than a DI engine for example where the injectors spray directly onto (into?) the pistons.

I've been told that this will not increase wear and tear on the IP or cause fuel leaks.

Shouldn't cause fuel leaks but WILL stress the IP more. For your desired 2400 PSI you are asking it to pump against approx. 20% more pressure than for even new injectors.

Wouldn't hurt to get a second opinion from another diesel guru.

[rlaggren]

> 2nd opinion...

That always makes sense... even a 3rd and 4th, then average the results. <g>

Most modded engines don't come with warrantees or live long in the great scheme of things, so any shop that works on them doesn't have to deal with many 50k mile call-backs. That may have something to do with their approach to upgrades...

Rufus

[asavage]

The VE IP's cam drive bumpers won't last with the added load. They don't even like WVO (ie more viscous "fuel").

Here's some from a Toyota VE-style IP I had rebuilt last year:

(click on image for larger)



The entire thread is here.

You've got to ask yourself: Why didn't Nissan run the injector pressure at 2400 from the factory?