Ok this may be a stupid question, but here go's. Does the aneroid adjustment have a direct relation to the amount of boost the turbo makes? If so how does one adjust this? Here's the deal, my 83 300D Turbo produces about ( I say about because I did not have access to a manometer) 7 or 8 pounds of boost at 70 MPH at 3K RPM on flat interstate highway. Does this sound OK or do I need to work on this to get optimum performance. One other thing that may be related my fuel mileage has dropped off to around 18 or 19 MPG it used to be 21 to 24 MPG. I know this is not a huge drop but when you cant trust the fuel gauge 40 or 50 miles on the trip meter makes a difference. If I tell my wife to fill up at 395.6 miles on the trip meter, she's not going to worry about fuel until 395.4 no mater what! Again any insight is greatly appreciated.

Keith,
I don't know if this will help, but this is from my 617.95 manual.

To check boost pressure, hook a tester up to the switchover valve with a "Y" connector, and drive the car in "L" or "S". Very briefly, increase the RPM's to 4000. I believe you will need to ride the brakes. You should also have the tester in the car with you(long hose fed through the firewall?) or have one that remembers the reading.

The boost pressure should be: 0.7-0.8 bar gauge pressure

To all: please expound on these directions if necessary.

I don't think the aneroid adjustment has an effect on the amount of boost your turbo outputs (I could be wrong). I thought it affected the amount of fuel delivered given a certain boost signal??? If you introduce more boost, an increase in the richness of the fuel mixture must also occur (aneroid adjustment?). Do a search for "boost check" or for posts by Richard Easley, one of his posts leads to a site that describes how to adjust the wastegate. I followed his procedure and my boost goes as high as 11 psi before the wastegate opens. The car accelerates better, but fuel mileage is the same. Your drop in diesel mileage be because of the colder climate. I permanently fixed a pressure guage in my car so I can monitor boost while driving. It's alot more fun than watching the oil pressure guage.

I have checked the boost so the next would be boost adjustment. I'll run a search on boost adj.

The general principal here is:

In a diesel engine, the only way to add power is to add more fuel at every time of injection. The only need the turbo satisfies, is adding more air which will allow the cylinders to run cool enough to prevent damage.

As the boost increases, a signal is sent to the injection system which provides more fuel, thus increasing power.

Theoretically, you could get just as much power from a non-Turbo 300D by squirting in the same amount of fuel. The only problem with this approach would be that the engine life would probably be measured in hours, or maybe even minutes.

Good luck,

OK I'm going to show my south Louisiana education here. the manual show's the spec. for boost to be 0.7 to 0.8 bar. What does this convert to in psi? Oh while i'm here I adjusted the trans. pressure cable to raise the shift point's, this has helped a great deal. The trans was shifting into fourth at about 25 mph!

1 bar is 1 atmosphere of pressure, 14.7PSI. So the
.8bar figure equals 11.75PSI - call it 12. It's
apparently common for the wastegate to go out of
adjustment on older turbodiesels, dropping the
boost to seven or eight pounds, or less. Buried
somewhere on my drive I have instructions on how
to adjust the wastegate.

The aneroid does affect the amount of boost produced,
in a limited way. It does not affect the maximum
boost you'll see at full throttle/high RPM. However,
it does impact how quickly and smoothly boost is
produced at low RPMs.

Boost management on the 617 engine is essentially a
closed loop feedback system. Boost pressure causes the
aneroid to adjust the amount of fuel injected. The
quantity of fuel injected raises or lowers the exhause
temperature. Raising the exhaust temperature spins the
turbine up more aggressively. Which increases boost,
which... You get the idea.

As adjusted from the factory, the 617 turbo engines
kind of "come on the boost" at about 2200 RPM. Adjusting
the aneroid to more aggressively richen the mixture
causes boost to start building much earlier, and come
on much smoother.

I adjusted the aneriod on my old 300D almost completely
rich. It no longer felt turbocharged. Rather, there was
plenty of power (torque, really) beginning at about 1100
RPM, and it built smoothly as RPMs increased. Quite a
bit nicer to drive - the engines response was more
predictable. None of this character where it has no
power one second, then the boost comes on and it takes
off.

There's tons of discussion around this subject in the
archives of the mercedes mailing list.
http://www.mercedesmailinglist.com

- Jim

This conversion website is courtesy of JCE on another thread.

http://www.convertit.com/Go/ConvertIt/Measurement/Converter.ASP

bar = 14.5037737730209 pounds per square inch
(pressure)