so how do you crank up the fuel on an OM617? - Page 3 - PeachParts Mercedes-Benz Forum

jbhebert · #31 07-06-2004, 11:54 AM

I'm either going to take some material off a spare set of pistons before I have them ceramic coated, or take some material off the head when I do the head work. A thicker head gasket might work OK on a lower compression motor, but even after the compression drop I'm still looking at 18.5:1 or so, and I don't want to blow out a head gasket.

dkveuro · #32 02-12-2005, 01:38 AM

A Pyrometer is a must when upping the power on any diesel.
Diesel will take lots of air to keep it cool.
The temp' reading should be taken just before the turbo exducer housing.

Temp's must not be allowed to climb past 1150 F.
Piston alloys melt at 1275 F.
Best life is 950 to 980 F on the flat and level at normal cruise.
Pulling a grade will push temp's higher but the previous applies.

Seeing 1300 plus F is not good, piston plasticizing is beginning at this
temp' as the combustion temp' is going to be 100 or so higher.

Cummins is a direct injection engine...most passenger cars are indirect or pre chamber
to run quieter and are 21 to 25 to 1 C/R to start easily.

One final thing....If you pump up the power you need to RETARD the injection timing
and lower the C/R about 20%.
My old LPS 1924, ran 14 to 1 C/R back in 1970 but was not turbo'd.

For eg: I built a 1984 300D for giggles a little while ago.(1994.)
It ran 38 psi boost and 580 psi cranking pressure .
I hogged out the head and skimmed a little off the piston crowns to reduce c/r.

I reduced the total injection timing by messin' with the advance mechanism.
A/C Delco rebuilt the IP and I had them move up the full load stop.( $680.00.)

Temp's where 900 F at cruise and 1200 at 5000 rpm....
It ran sub 10 second 0 to 60's and wound out to 5300 rpm in high gear.(110 plus.)
It would eventually overheat in summer at 90 mph with the a/c on, but backing down to 70 would let it cool off to 90 C.

I debated an inter cooler but the job was too complex.
I lowered the boost to 19 psi and a local doctor bought it after I lent it to him as a loaner.
He came back with a silly grin on his face and asked to buy it.

He ran it 5 years, last I knew....

boneheaddoctor · #33 02-14-2005, 10:45 AM

Great info here................

#34 04-27-2005, 07:38 PM

My ALDA has been completely maxed out and yet I STILL had no black smoke at all (Running lean). So, I fiddled with the external full "throttle" travel stop by screwing it in 6mm. I then adjusted the linkage to match.

Now I FINALLY have a slight trail of black smoke under full throttle until boost kicks in. This was not just a small adjustment, this was like a whole ALDA adjustment all over adain!

Not only was there a performance gain, my cooling problem (Or lack of) has gone away with it. Insted of taking all day to reach 80*c it will now get there in a few miles.

I don't recommend everyone do it, I'd just like to pass it along for future reference.

Fredmburgess · #35 04-27-2005, 09:11 PM

...hmmm, so I guess I better get a exhaust temp gauge in there eh?

I'm running some minor changes in the 300SD - a CCW turn on the ALDA adjustment, boost to 15 psi max (from the whopping 8 it was making when I got the car), 3" diameter intake pipe and a K&N filter (good riddance to the hideous stock A/C housing). Pretty mild changes compared to some of the above but I do tend to thrash the beast down the highway. Turbo whine is a crack up. I'll let you all know if anything goes BANG in the night...!