[s-cars] Wastegate Frequency Valve (N75)

[Theodore Chen]

kevin,

i'd suggest searching the list archives for some discussion on this earlier
this year, but the reformatting of the files has nixed google's ability
to search the archives, and the built-in search engine isn't that great.

disconnect the WGFV from the wastegate.  i disconnected the silicone hose
at the WGFV end and left it open to atmospheric.  i also put a small
hose on the WGFV nipple and clamped it shut, so that i wouldn't have a
leak that might affect the air/fuel mixture.

you can also disconnect the WG-WGFV hose at the WG end, which is a banjo
fitting, and then clamp that hose shut.  that hose is expensive and difficult
to get, so i didn't want to risk putting a clamp on it, but i was probably
being overly cautious.

i consistently got a ton of boost after doing this, so i knew my low 
boost problem wasn't due to an intake leak.

my WGFV passed the output test (it clicked normally) but after checking out
a bunch of other things, i suspected that the old WGFV was working fine
during the output test and intermittently failing at high temperatures and
high duty cycles.  i bought a multimeter with dwell measurement, and used
it to verify that the ECU was calling for higher duty cycles.  so i replaced
the WGFV, and that fixed the problem.

the output test isn't very helpful for verifying that the WGFV is good.  it
actuates the WGFV briefly about once every second, which is a far lower
duty cycle than the WGFV sees in operation.

a new WGFV is about $70, so you might just want to replace it instead of
spending a lot of time verifying that it's good.

-teddy


--- Kevin Barnett <bluevr6 at yahoo.com> wrote:

> HI oh Guru's of the AAN:
> 
> I am still chasing my boost leak / 5 psi issue.
> 
> If I unplug the N75, I get teh same behaviour as if
> plugged in.  As I am running a second used valve
> provided by a friend through my mechanic (thanks Rob),
> if I jump across the wire connectors, will it override
> the valve circuit so that I can run the car briefly to
> see if the valve failed?
> 
> Ideas, suggestions, incantations appreciated.
> 
> Thanks,
> Kevin
> 94 S4 - not happy.
> 
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