[s-cars] Forge BPV's ??(diverter valves)

[Stephen Redford]

---Does this info apply to all BPV's , the Forge included , or is it in reguard to another brand / style which the people at Turbo XS use ?  Also, would one of these Forge Valves fit an  ' 85 Urq ?  Would there be a better setup for the old ' 85 than what the S-Car people are talking about on this string ?  Thanks  in  advance .....  Stephen Redford  ' 85Urq u.s.model with no manifold pressure relief .
----- Original Message -----
From: <CaptMagu at aol.com>
To: <joeamund at online.no>; <S-CAR-List at audifans.com>
Sent: Friday, January 31, 2003 8:03 AM
Subject: Re: [s-cars] Forge BPV's ??(diverter valves)


> Joern and Mike
>
> This was originally posted to the kremmer list but I thought some of you
> would enjoy this too.
>
> Joern, get rid of that Bosch unit before something gets sucked into your
> turbo. First things first.
>
> On the charge air line running from the turbo to the I/C we have a 28mm bib
> plumbed to a section of 63mm aluminum pipe. The BPV is plumbed between this
> charge air pipe and the turbo inlet. Additionally there is a vacuum line bib
> at the top of the valve that is pressurized from the intake manifold. As the
> biturbo list diverter valve test and article reveals the piston type valves
> can be plumbed either of 2 ways. We had them plumbed conventionally with the
> charge air pressure line feeding into the bottom of the valve against the
> spring. The problem here is that in high flow(make that Happersized turbos)
> you get too high a pressure differential. The boost pressure within the
> charge air line pushes against the piston/spring and intake manifold pressure
> from the top to prematurely open the BPV. This pressure differential exists
> because we are approaching if not exceeding the throttle body and intake
> manifold's ability to handle flow.
>
> This wasn't that much of a problem for me before that Mike Pederson talked me
> into cleaning up my intake tract with the Pederhousen Big MAF and the fluting
> to my I/C. Since the cleanup, I now flow significantly more air and thence
> the problem with the throttle body/intake manifold. We've got all this air,
> we just can't get it all to the very clean head.
>
> I have recently talked to the techs at TurboXS and they did indeed state that
> for big hp applications they now recommend plumbing the valve backwards or
> sideways. The charge air line is now plumbed into the side of the valve. The
> TurboXS valve does have a split piston with a shaft inbetween. With the
> charge air coming in the side it pushes against one side and the other. This
> nullifies the effect of the pressurized charge air. When you shift and go to
> vacuum, the top of the piston is pulled up, activating the valve and divert
> ing the air to the turbo inlet.
>
> Finally, one last thing. On the stock urS-cars the turbo to crossover pipe
> hose has the plumbing for the BPV. It comes off the curious snake hose affair
> on its way to the MAF to turbo inlet hose. Why did Audi plumb this loop in
> there? A lot of other applications also have a similar extra hose plumbing.
> Curious. That's all I know about BPVs, honest.
>
> Hap, no longer prematurly bypassing in Evergreen, Maguire
>
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