EXACT compression for a 617 NA and turbo?
 

Ok i know the turbo 617 is around 425 new from the factory now whats the non turbo 617A rated at? i know the bore from 1976-1985 changed along the way from 3007cc or so to 2998cc so whats the comprsssion difference?

The compression is about the same for both, 21.5 to 1 I believe.

Tom W

The factory's "Technical Data/Passenger Cars" (April 1985 Edition) on page 106 gives the compression ratio as 21.5 to 22 for all diesel engines.

The turbo engines have a 0.5:1 higher compression ratio.

Um i was asking in psi sorry i didnt clear that up.

425psi on each cyclinder is basically new for a turbo 617.......what is it for a non turbo?

I thought 450 PSI was new... approx 30Bar...

Not according to the factory
 

615, 616, and 617 engines have compression 21.5:1
601, 602, 603 engines have compression 22:1

regardless of NA or turbo.

There is no compression difference between, for example 617.912 (NA, 88 HP) and 617.952 (Turbo, 125 HP), according to the Technical Data manual referenced in my earlier post.

Jeremy

That is false.

OM61x.91x is 21:1
OM617.95x is 21.5:1

So the psi in each cyclinder is the same as for non turbo and turbo ...i always thought the non turbo was higher.

Forced, please identify your source.

My source (see attached photos) is "Technical Data/Passenger Cars," April 1985 edition. The version that I have is a USA reprint (c) 1990 Mercedes-Benz of North America and Mercedes-Benz of Canada, part #2364. It covers models 107, 123, 124, 126, and 201 and includes (for us diesel-heads) engines 615, 616, 617, 601, 602, and 603.

Jeremy

Mercedes service manual. page 030/1

Yours is probably another error in the translation. The manual also says the 116 300Sd has a 170hp om617 when we all know it does not.

MY service manual dated 1987 says that, as much as I hate to admit this, that Forced is correct. 617.912 is 21.0 and 617.952 is 21.5

Don't know why you need to know the psi when factory new but generally you check psi between cylinders to see if there is excess wear in one cylinder and don't pay much attention to the number only the difference.

What's a half a compression point amongst friends?;)

He did ask for EXACT numbers though.

Tom W

Just bought a compression tester, so I'll join the discussion by asking..

What psi/bar-ranges would indicate major trouble? What is normal readings?
I have two 617's (.910 & .912) and a 616.934, they're well worn all three of them. At what point should I know on the gauge glass and mumble "uh oh"?

Valves are adjusted on all of them.

My opinion FWIW is that you want to look for at least 300 psi and the readings should all be within 10% of each other. Anything much below 300 is probably getting pretty well worn. For example my 617 turbo engine lost compression in one cylinder (100 psi) and the other "good" cylinders were down to about 250 psi; telling me that it was pretty much worn out (438K miles). This engine would still start with no problem down to about 10-15F (before it lost one cylinder), below that you had to plug it in or really work at getting it started.