The ARV leaks pressurized air from the comprssor outlet to the compressor inlet. I heard it has something to do with getting the trap oxidizer to operating temperature quickly. Whatever.

The ARV consists of a piston with a coil spring pushing it against a post in the compressor outlet. There is a membrane around the piston enclosing a chamber subject to vacuum. When vacuum is introduced to the ARV, the vacuum overcomes the spring retracting the piston which allows pressurized air to leak to the the compressor inlet. I don't know if under operating conditions there is enough air pressure to overcome the spring. If so, drill the ARV for a whistle and you'll have yourself a BOV

Removing the vacuum signal should render the ARV inoperative but I found in my 87 SDL the piston was deformed and not properly sealing the compressor outlet port. To make sure ARV is disabled, I sent a 1/2" plug into the compressor outlet port. The compressor inlet port is a slot (arc from 2 o'clock to 6 o'clock in the photo) which I didn't know how to seal. With the outlet port sealed, it shouldn't matter.

If that seems severe, put a stronger spring behind the piston and/or add shims for more spring pressure.

edit - I forgot to mention, I put the ARV back in place. You'll draw unfiltered air through the ARV cavity if you don't reinstall at least the cover and cap the vacuum port. No need to cap the port if you refit an untorn membrane.



Sixto
87 300D