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Originally Posted by DieselAddict
I recently did an experiment with the injectors in my 87 300D. I had been battling a significant combustion knock at idle for over a year and just about trying everything. The only thing that temporarily killed my knock was bringing the car down to a lower elevation (over here I'm at 4500-5000 ft) or running the car on Diesel Purge. Twice I inspected and balanced my injectors to no avail.
Recently I was also rebuilding the injectors in my two W123 diesels and I noticed the nozzles used in those engines are different from the ones used in the OM60x engines. The OM616/617 engines use Bosch 240/ nozzles that have a crosshole on the side of the tip of the pintle and an exit hole on the tip of the pintle. The OM602/603 engines use Bosch 265 nozzles whose pintles have no holes and they just have a longer tip. From my testing I found the 240/ nozzles produce a very fine spray while the 265 nozzles spray more like a garden hose with a thumb placed over the opening and I tested both used and new 265 nozzles. So I decided to use the 240/ nozzles even though they are not the right part for this vehicle, but I'm quite pleased with how the car runs now. The combustion noise at idle has been noticably subdued and it's a lot more steady and consistent. The car has about the same acceleration as before. The only possible downside that I noticed is that during deceleration just before the engine reaches idle speed the diesel clattering now comes and goes but I think I'm hearing it less as I drive the car more and it's possible it was caused by carbon buildup which may be getting cleaned out.
My question is, why did MB or Bosch get rid of the crossholes while designing the 265 nozzles? IMO they are essential for producing that fine spray that the 240/ nozzles have.
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Having rebuilt MANY injectors for people, I've seen this same thing. The 265 in the later 602/603 engines has a long pintle that is similar to the older diesel nozzles and to the later VW ones.
Two things, the 265 has a different flow rating than the 240/ and the 603 has a different pre-chamber dispurser. Their "theory" is that don't want "too fine" a mist as it negates what the dispurser does, so the more concentrated flow from the 265 is intended to be directed to the dispurser ball and atomize from the collision. If you look at charts of "proper" spray from an IDI injector, it's not very atomized. The pre-chamber ball is supposed to do that.
The reason is probably because the pre-chamber lasts a LOT longer than the nozzles and cost about the same between the engines. Making nozzles like the 265 is cheaper than making the 240/ with the precise center and cross holes. So they can make them cheaper and save a LOT on mfg costs and pass off the fine atomization to a long-term part of the engine.
Anyway, like you, I've tried the 240/ in not only the 265 applications but also the 193, both to positive effect.
Only problem might be that the flow is different and could cause some issues down the road (but it seems some of that could be mitigated for with pump adjustments and so forth) and finding the 240/ nozzles is impossible as the only thing currently available in NEW is India made.
Soooooo....., just when you find something that works great for SVO/WVO and atomizes well in 603's and VW's with better mileage and slightly increased power, then Bosch slams the door shut. Assh*les!