Originally Posted by piccolovic

Don't know if this was covered, but there is a diaphram in the exhaust system. I had the same problem on my 1976 220/240D. It was the last year they had the diaphram. When I sold my car to Pierre Hedary, he immediately went for that part, which he said was non-existent, as it was so eroded. I had been getting 30-33 mpg in high altitude but got a blast of black smoke out the tailpipe taking off from stop signs. After Pierre replaced the diaphram, the black smoke went away and fuel mileage went up to 36 mpg around Miami. Pierre also told me that because this part was hugely forgotten, most people tried everything and spent lots of money trying to fix the problem. Try this first, before messing with IP fixes, or otherwise other expensive repairs.

Originally Posted by Phil_F_NM

I was thinking about this and since the pneumatic governor operates on ambient pressure there is no way to put a turbo on since it would not build vacuum in the venturi.

It all comes down to that way the spring pushes against the diaphragm and how to make the IP think the air pressure is greater. The only way to decrease the smoke and increase fuel efficiency now is by changing the spring out to one with a softer response. Problem is my acceleration will be awful so I will just deal with the way it runs right now and in a month will be heading back to sea level.

Phil Forrest

Originally Posted by Phil_F_NM

Ok, so I'm moving back to New Mexico for good this time in a few months.
I'm **hoping** there exists a factory adjustment for the OM615 which has a pneumatically governed IP, when run at high altitude. I don't see why there wouldn't be.
No, I'm not going to stick a turbo on this motor. I'm hoping to not have to change the IP out to the kind on a 240D with ADA but in the long run (a few years down the road when i can afford all those mods) that may be the answer. Frankly, I'd rather stick a whole fresh 240 motor in, if that's the case.

Thanks all.

Phil Forrest