Mystery intake flapper valve?

gschwenk

Active member
Joined
Feb 11, 2008
Location
Pensacola, FL
TDI
'97 Passat TDI
Well I have the front of the engine torn apart on my newly acquired '97 Passat and in the air intake box is a flapper valve spring loaded closed that runs to a plastic hose running toward the firewall...Anyone know what it does/supposed to do and would it do it better if I surgically removed the valve? In my world the more air the filter sees = lower EGT's and all that.

Thanks,
Geoff
 

compu_85

Gadget Guy
Joined
Sep 29, 2003
Location
La Conner, WA
TDI
... None :S
Leave it there. That's part of the warm up system... when the engine bay is cold the airbox draws air from behind the exhaust manifold.

-Jason
 

gschwenk

Active member
Joined
Feb 11, 2008
Location
Pensacola, FL
TDI
'97 Passat TDI
Makes sense, I was surprised how stiff the spring was on it, but if it's connected to the exhaust manifold back there I suppose it would need to be...I imagine it connects post turbo right?? I could go follow it but I'm especially lazy today.
 

paramedick

TDIClub Enthusiast, Vendor
Joined
Jul 29, 2001
Location
Versailles, Kentucky
TDI
2015 Audi Q5 TDI
compu_85 said:
That's part of the warm up system... when the engine bay is cold the airbox draws air from behind the exhaust manifold.
Nope. The door is there in case the front snorkle becomes blocked by trash or snow. The door will open if the vacuum in the airbox reaches a certain point.
 

gschwenk

Active member
Joined
Feb 11, 2008
Location
Pensacola, FL
TDI
'97 Passat TDI
Well if that's the case I'm taking that bad boy off of there...I'll get under there tomorrow and see what I see...I really appreciate the input.
 

paramedick

TDIClub Enthusiast, Vendor
Joined
Jul 29, 2001
Location
Versailles, Kentucky
TDI
2015 Audi Q5 TDI
Sure. Just be aware that the airbox will be sucking hot engine compartment air rather than cold air as designed. May impact economy and performance.

Now if you close up the hole into the airbox......
 

redmondjp

Veteran Member
Joined
Jul 1, 2004
Location
Redmond, WA
TDI
'96 Passat Sedan
So your '97 has a plastic snorkel going back towards the turbo? My '96 has a steel pipe there. Since I live in Puget Sound and seldom drive in the snow, I have removed the pipe from my airbox (makes access to the timing belt WAY easier :) ). The idea is that if the snowscreen becomes clogged with snow, the increased vacuum inside the airbox will cause the flapper to open, pulling warmed air from around the turbo inside the airbox, and this will eventually melt the snow in the snowscreen.

But I have the snowscreen removed also on mine, so that flapper will never come open unless the air filter becomes plugged (and I have a filterminder to monitor for that).
 

jck66

Top Post Dawg
Joined
Jan 4, 2001
Location
Greenwich, CT, USA
TDI
12 Passat SE / 14 BMW 535d
Geoff, it's not hurting anything to be there, and removing it won't help you get more air into the engine. Why not leave it alone?
 

gschwenk

Active member
Joined
Feb 11, 2008
Location
Pensacola, FL
TDI
'97 Passat TDI
Because it's not in my nature to not attempt to improve upon the design of the vehicles under my care.

The tube just stops in the engine compartment, supporting the idea that it's there in case the snorkel get's clogged...It'll be coming out shortly. Weight savings = fuel savings :)
 
Last edited:
Top