QCRAZY

There *should* to be a check valve before the branch (coming from the right side) or you will pressurize the branch (crankcase) under boost.

The verturi would act as a restrictor to boost but I would hope Audi would include a check valve prior as well.

If they didn't include a check valve I would dump that thing if I had a turbo engine.

QCRAZY

It's in 1.8T's, 2.7T's, 2.8's, and 4.2's....they all have it. They all use the same part number even.

The configuration required to make one a lucky winner isn't known. It appears that all NA cars get and only auto turbo cars get it. But who knows with Audi.

Here's the 4.2(#21)...
<img src="http://www.elcats.ru/imaudivw/VAG04F13.giF">

Eric 2.7

It's a little hard to see, but the wedge has separate check valves for each side, but they only check the feed from the brake booster connection.

Good thinking! I think you are on to something. From this design, there is nothing to prevent the manifold from pressurizing back through the branch when it goes positive. This may be part of the problem. I may at least buy and place a check valve in the branch line to prevent that.

I have not quite convinced myself to eliminate the suck pump yet, but at least a check valve would help.

QCRAZY

...I saw the check valves, I was just hoping there was one in the portion you didn't pull apart. I wouldn't want to be pressurizing my crankcase.

Luckily, my 2.7T doesn't have one of these. And I don't give a crap about my 2.8's

BTW, here's an Audi check valve; 078 905 291 A, $10.

Eric 2.7

Thanks for the part # ! I was just going to start looking.