I have an '82 240D. While replacing the air filter, I noticed that the opening for the intake has a throttle plate similar to what you would find on a carburator; it opens and closes with the movement of the throttle. I always thought that diesels didn't operate with throttle plates and engine power was regulated with the amount of fuel injected into the cylinders. It would seem to me that this is a restriction of airflow into the intake manifold. What am I missing?

Herb
'82 240D
112,000 miles

It's the induction of oxygen that causes acceleration in a diesel. The fuel should be a static amount, which just gets delivered faster as the engine revs when more oxygen is added. That throttle plate meters the amount of oxygen delivered to the combustion chambers.

FWIW, my old '81 240D never had that plate and my current car does not have one either. However, the '82 and '83 240D's in our house do have the plate. I always thought it was part of the egr system. I respectfully disagree with Mike's comments, but I am not a tech so I won't offer the truth either. I'll shut up now.

[Edited by SW on 04-25-2001 at 03:45 PM]

As stated it's for EGR system!! MB diesels(after 1975) can run just fine w/o intake manifold on the engine.

D'OH.

I stand corrected :o. I guess that's what happens when you get confused.

Removal of throttle plate
 

Then, those of us that do have the throttle plate at the opening of intake manifold can theoretically remove or somehow keep the throttle plate open will improve the breathing of the engine. I do know that the EGR has been disabled on this car.

Has anybody in the group done this? Just wondering.

Herb
'82 240D
112,000

I could be wrong on this, but I'm pretty sure the throtle plate is part of the pneumatic govenor system for the early style injection pumps. I have a 71 220D and the associated MB engine manual and that is what is shown there.

Bob D.