AAN Engine Vacuum Hoses and Related Devices

[UrS4boy]

888

[A80Avant]

The N80 valve is one that i still use with VEMS, but since vems does not allow for a DC for it, rather than an ON/OFF function, i noticed that it was unusable for casual driving. So i only apply it on overrun now to burn get the fuel vapours into the inlet manifold that way.

[cooperquattro]

scrap the lot!!i dont use any..

[martinjs]

The hose that goes through the bulkhead on the left of the engine bay..where does it go? I presumed it was for the boost gauge in the dash computer but it isnt.

[cooperquattro]

goes to map sensor in ecu?

[martinjs]

No, that goes through the bulkhead on the right with the diff line.
Ive ran the car with the left hose disconnected (the t piece it connects to snapped) boosts ok still, just wondered where it went.

[UrS4boy]

The hose that goes through the bulkhead on the left of the engine bay..where does it go? I presumed it was for the boost gauge in the dash computer but it isnt.

The dash computer gets its signal from the ECU. The hose to the brass nipple on the ECU is a green plastic from the intake manifold, through the bulkhead to the ECU via the moisture trap (in the engine bay for the UrS4 and by the ECU for the UrS6).

[martinjs]

Yeah, i thought the dash got its own feed from the inlet manifold, so where does the left side hose go?

[UrS4boy]

Yeah, i thought the dash got its own feed from the inlet manifold, so where does the left side hose go?

I am at a bit of a loss because I have a LHD car and you have a RHD car and I am not sure where your ECU is or even which "left" you are talking about (when facing the engine bay or when sitting in the car?). All I can say is there is a vacuum path from the intake manifold to the ECU, with a T to the fuel pressure regulator, to the moisture trap and then into the ECU, i.e. 22, 23, 31, 32 and 33 in this diagram:

[martinjs]

I know about the fuel reg and ecu line, ive just snapped a pic of the hose im on about, the feed from the manifold splits at that black t piece, then one goes through the bulkhead like you can see in this pic and the other goes to the right and connects to a black plastic line (diff?)

[UrS4boy]

I know about the fuel reg and ecu line, ive just snapped a pic of the hose im on about, the feed from the manifold splits at that black t piece, then one goes through the bulkhead like you can see in this pic and the other goes to the right and connects to a black plastic line (diff?)

I am not sure where that line goes. I went out to check my LHD 93 S4 and I don't have that line per se. What I see is a vacuum line that is likely related to the automatic climate control system.

However, what I do see in your photo is a lack of a clamp on your moisture trap. This could be robbing you of 70 hp or more.

[newsh]

Aircon has a vac line and so does the evap system.

[martinjs]

However, what I do see in your photo is a lack of a clamp on your moisture trap. This could be robbing you of 70 hp or more.

Ive just done an engine swap and am in the middle of replacing all these hoses hence why no clamps are present.

Aircon has a vac line and so does the evap system.

Im guessing thats it then.

[Wheeljack]

My LHD CQ has a vacuum line running back to the differential control module on the drivers side. It has its own vacuum reservoir as well. There is another vacuum reservoir in the drivers front fender well that supports the recirc solenoid on HVAC box.

[Zoig]

There is another vacuum reservoir in the drivers front fender well that supports the recirc solenoid on HVAC box.

What is the best place to tap into the recirc hose?
I need to connect up the rear diff, but I am missing the rear reservoir, so I was thinking of using the recirc reservoir for that (I presume the recirc also has one way valve installed).