PeachParts Mercedes-Benz Forum - View Single Post - "Tweaking" 1987 300SDL

Diseasel300 · #2 04-05-2018, 01:48 PM

2 things worth checking:

1: Check the ALDA on top of the injection pump. Try pulling a vacuum on it. If you can't pull a vacuum, or if you can and it quickly bleeds off, you may consider re-sealing the unit. The ALDA senses boost pressure and enriches the fuel mix to spool the turbo. If it leaks, it'll be pretty doggy until the turbo spools then suddenly have a burst of power.

2: Check boost pressure. SDL's should be running around 13-14PSI when in gear and pulling >2000 RPM. If boost is low, or builds late, you'll be smoking more than you should AND you'll have lower horsepower (and greater fuel consumption).

It is also worth checking the port in the head for the boost sense line to the ALDA. They frequently get blocked with soot/tar/oil.

For what it's worth, I have my IP tuned pretty tight (though it comes from a 3.5L engine). My SDL does ~24mpg in city traffic with the A/C running. Highway driving depends on the weather (A/C or no A/C) and speed. 70-75mph with no A/C (late fall, winter, early spring) I can pull 29-30mpg. 75-80mph and A/C running is more like 25mpg. Remember, this a barge of a car with no lockup torque converter.