Boost Pressure Settings on 5 cylinder (617) diesel engines
 

I have seen numerous postings on the internet regarding the boost pressures at which people have been setting their engines. While it is true that most engines are running well below the factory specified pressure, there are quite a multitude of statements as to what the actual specification is. Various people have stated in various postings that the factory specification is 10, 11, 12, or 14 psi, or .9 or 1.0 bar. Obviously there is only one correct answer as to the *actual* factory specification. I have included the following chart sourced from the MBZ service CD.

As you can see, the maximum pressure (at the high side of spec) tops out at .75 bars, which equals about 10.9 psi.

Many people feel that the factory specifications are conservative in consideration of reducing stress & thereby prolonging the life of the engine. My question is whether anyone has done any *actual* testing with a pyrometer to see what is truly a safe range of pressures at which to set these engines. Of course the fuel enrichment setting for any particular engine will have a great deal of influence on the exhaust temperatures, but does anyone either have data, or know where to find data on higher boost levels? I’m sure that I would not be the only one to want some definitive information on this subject.

Thanks in advance!

RTH

Well, I tried to attach the image as a bitmap file, but it is too big. I’ll try to figure out a way to reduce the size and then post it as a follow up.

Sorry ‘bout that.

RTH

Duh… I’z dun figgerd it out…
 

Here you go:

Looks like nothing is gained by increasing the boost past the factory recommendation.

Remember, this is MB, not GM -- if they say 0.7 atm is the limit, believe it. If the engine would stay together reliably, the factory recommendation would be higher.

I have it on good authority that one should DEFINTITELY not exceed 13 psi on a 617, and 13 psi is only to be used for very short periods of time (as in passing once in a while). Rod and or headbolt failure is certain if overboosted for any length of time.

Peter