(EGR) removal related question - 82 240D
 

I'm in the process of changing a head gasket on my 82 240D and while I have everything off decided to remove the emissions garbage. I removed the egr valve and make a blank off plate to cover its hole on the intake manifold. I made a blank off disk for the exhaust manifold port.

Now for the question. Inside throat of the Intake manifold is a butterfly valve that is run off the throttle linkage, is there a reason to keep this butterfly valve or is this just part of the emissions gear? Being a diesel I would think that it would be better to remove it and let the engine take in as much air as possible. Any thoughts?

IIRC the 240D never had an EGR. got a pic.. unless you put an om617 in it

I may be refering to it wrong. Under the intake manifold is an attached valve (EGR?) that lets exhaust gases back into the intake. I removed this valve and blocked off its ports. Its a 616 4 cylinder.
Thanks.

thats new to me

Remove it. If you look closely you will see two screws holding it in place. Remove the screws and the butterfly will slide out.

Thanks, I already removed the screws and removed the plate. Just wanted to make sure it wasn't there for any other purpose before I re-assembled everything.
Thanks again.

My 83 240D has a EGR (sorta hidden under the air filter) and the butterfly "throttle" too. I have the EGR blocked and the butterfly and related linkage removed.

240D EGR vacuum tubes.

I believe that the "butterfly" valve was installed at the factory to help prevent the engine from running backwards. There was some discussion about this some time ago, may have been related to the run-away threads. Looks like these were also installed in the 220D's as well.

It's installed on the W123 240Ds to restrict the intake for more exhaust gas flow into the intake manifold. If it were to prevent reverse running, it would have also been on the 77-81 engines and the OM617 engines as well.

It's on the W115 220/240D because the injection pump is pneumatically governed instead of mechanically. EDIT: 200D, 220D, and early 240D tuning guide

The engines cannot run backwards. AFAIK, the only on-highway engines that are physically capable of running clockwise and anti-clockwise are the Detroit 2-stroke series engines.

ForcedInduction is correct, the butterfly creates lower pressure in the intake to allow gas from the exhaust to flow through the EGR. It was not required on the turbo due to the higher exhaust gas pressure upstream of the turbocharger. How could a "butterfly" valve prevent reverse rotation?