What is that vacuum device?

[tlake]

What exactly is that item attached to the left side of the intake manifold in the pic below. Is it vacuum related to keep the revs up when the a/c is on

530iEnginePic

[528i-1981]

I think it's the vacuum limiter for the EGR. From what I've read, this prevented the EGR valve from opening too aggressively an cause excessive exhaust recirculation disrupting the mixture and affecting performance, especially at idle. This is just based on research, my 81 528i does not have this device.

[Mike W.]

That's the gulp valve. It prevents backfiring on deacceleration. I suspect 530's didn't have coasting fuel cut off which 528i's did. 528i's cut fuel off above ~1300 RPM with the throttle closed.

[tlake]

Thanks 528i-1981 and Mike W. I think it might be on all L-jet Euro cars too pre 1981, that didn't have the fuel cut off system. Might have to look at some Euro/US articles on the early 528i.

Yeah, from article pics it seems the 1979 US / Euro cars have the gulp valve too.