PeachParts Mercedes-Benz Forum - View Single Post

2.5Turbo · #5 09-08-2007, 12:11 AM

Yep, that big "brass nut" is the pressure switch. The only other thing on that end of the manifold is the boost pressure line to the ALDA and pressure sensor.

I'm not sure which one goes where as my car is 2500 miles away at home. I know there are two vacuum transducers between the airbox and the expansion tank, but I can't remember which one is which. Somebody else should chime in shortly with the answer. The flapper/butterfly valve between the turbo and the EGR is there to make the engine draw more EGR gases when needed. It closes off the intake somewhat which makes the engine draw more gasses through the EGR.

When no pressure gets to the ALDA (like when the overboost system is activated), the fuel is limited to the performance of a NA engine. Some boost will be built with no signal to the ALDA, but there isn't enough fuel being burned to raise the boost to unsafe levels. I haven't actually done any tests, but I would think only a few PSI are built with no boost signal to the ALDA.