Hey all!

I'm working with Mercedes Diesels trying to extract power from them. The Diesel Gods over in Finland have done some absolutely mind blowing things with their MB Diesels but unfortunately they are extremely tight lipped about what they do.

I've done the whole intercooler, intake/exhaust, injectors and custom turbo thing but modifying delivery valves have recently been brought to my attention. Our engines use the Bosch MW-Pump and currently fuel flow seems to be the limit at around 180hp with the rack limiter arm removed.

One Cummins person on an MB tuner forum suggested cutting off the collar below the valve seat saying that it restricts fuel flow and we can gain some significant power with that modification. On the head of the stock DV is stamped 112 008. I'm not aware of any aftermarket parts that will swap in so we may be limited to modifying existing parts.

The real questions here today are: What are the benefits and risks associated with removing that collar? Does injection timing need to be advanced/retarded to compensate for the higher fuel flow? and what kind of gains might be possible by changing only the DV's?

Thank you! I now return to searching the forum.

 

Well he is somewhat right, the higher flowing valves are shorter, with deeper grooves, and a less aggressive shoulder. IF you can get another set of DV's, you may want to try grinding down the shoulder, if that gets you a little more power, move on to deepening your fuel channel, and that should get you more fuel. A little bit goes a long way here, don't get too aggressive. You can search the topic here or on some other forums to see just what the difference in DV profiles is.

As far as how much power you can make changing them, a lot. Us 12v guys have been swapping them for a while, and with a big enough turbo you can pick up well over 100hp out of a set of full cut, laser cut, or hi-flow DV's. With your smaller engine you could still probably pick up 50-100 hp, depending on how restrictive the stockers are.

As far as timing goes, as far as I know the old MB's are all IDI motors, so advancing the timing a little might help with atomization, but not much else.

Thinking about the collar removal, if you happen to open the DV too much, and your injector never closes, you might risk washing the cylinder wall of oil with fuel, or even worse, locking the piston from hydro-lock, where there is so much fuel that is still liquid it can't be compressed. I'll admit, I've never seen this happen on a typical engine, but we did have it happen once on a tractor when the fuel pump stuck on and the carb float never closed, the cylinder filled with gas when we started it and locked the cylinder, the rod went right through the crankcase.

 

Very useful information so far!

I've already played with the timing a bit. Stock is 24*BTDC and I've settled at 26*BTDC for now. I've had it up to 30* but it was difficult to start and made more rattle than power.

Does removing the collar alter injection timing and/or duration or just how much fuel can flow past it?

Just to clear up terms so I know exactly what you are talking about, which part do you refer to as the grooves, collar and shoulder?

 

Your grooves are the scalloped shaped flutes running the length of the valve to about half way up, just below your collar. Your shoulder is the same thing as the collar, I just got tired of calling it that, .

Removing the collar will alter your duration, as it will allow more fuel to enter the injector, you could have the pop off pressure raised a bit to try and atomize the fuel better, but I don't know how much it would help on an old MB. Your timing shouldn't be effected at all.

Like I said, I wouldn't touch anything until you have a set of stockers as a backup. It might be worth polishing them as well, as in your picture they look fairly rough (but that could just be the camera). Fluid dynamics get effected quite easily by small areas of turbulence like that, so it might be worthwhile.

 

WOW, that released a LOT of power! I'd say it's easily 25-50hp.

One problem is EGTs are WAY up. I used to cruise the highway at 600*f at 70mph but now its up to 900*f. I can easily hit 1250*f in a heartbeat and I'd quickly peg the gauge if I keep going. I couldn't do a 0-60, by the time it was at the top of 2nd gear it was already past 1250*f.

The video is a WOT acceleration from 65-80mph.

The other problem is the idle lopes really bad like a g@sser with a hot cam.

But once the turbo hits 15psi it takes off like a monster!

 

Ya got to take the bad with the good..

 

Yeah, I thought I mentioned that ... No such thing as a free lunch!

 

Maybe Methanol or water injection would cool things down a bit for him?