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Re: All those valves
In a message dated 96-02-28 17:56:43 EST, you write:
>This is based on my experience with the Merkur turbos. Some of you know
>stock they have no IC and therefore no bypass, pop-off or whatever.
>Many have added an IC and with it a bypass valve. There is only one current
>the shelf IC kit for the cars so most run with that bypass valve. The valve
>from Spearco is very much like a 944 turbo, S6 or Saab bypass. Its problem
>the points from where it gets the boost it recirculates. It connects from
>outlet elbow at the turbo back to the inlet. Not really good enough. Better
>pick up farther downstream. You get more to return and you don't leave the
>intercooler and all the plumbing full'O air. Friends have added a pick up
>as close to the throttle plate as possible and re-routed back to the turbo
>inlet. Much better.
Agreed, some discussion over the advantages, but the pressure spike
originates at the t-body, so nabbing it there is best
>I use an HKS bypass mounted close to the throttle plate and back to the
>The HKS can flow a greater volume than the Spearco and through a larger hose
>back to the inlet.
And is biggr than any of the audi offerings tooo
>We don't vent to the atmo. Our cars have a vane type air meter with a
>door in it. If you vent the bypass or a pop-off to the atmo the door in the
>meter suddenly opens too much and you get an overrich condition during
>This means you have to drive through all the fuel. It does slow progress.
Injection here.... 86> audis have something called an deceleration valve
that eliminates that prollum.... It is a selenoid connected downstream of
the airflap (like right above it) that vents back to the air box..... It
opens when the idle switch is activated, and does not let the overich
>I've tried both the bypass and a pop-off vented to the atmo and I've seen
>richness both in my air/fuel meter and the seat of my pants. And why do it
>anyway. Well for the sound but........
Well, there is the turbulent air theory, but for a street car might agree
with the why....
>So I wonder, does the Audi need a bypass. Compared to the Merkur the turbo
>routing is very short so you don't need one for the hitching problem. It
>reduce spool time during upshifting though.
IC blowout and T-body hose blowout and turbo stall, pressure braking.....
Any/all a problem.......
>And I wonder with the CIS would venting to the atmo cause the sensor plate
>lift and richen as well. Maybe.
In pre 86, yes.......
>The length of the turbo plumbing on the S6 makes the Merkur look good. I
>amazed the long tubes don't add to the lag more than they do. But the S6s
>bypass. I've found during both my weeks with S6s that they are very
>That little turbo is working well. The Saabs are also nearly lagless, the
>low boost version especially.
>I imagine a 10/20 valve 5000/200 with very short plumbing and a K24 would
>as near to NA as possible. Maybe.
......Maybe..... K24 doesn't do it all....