# Definitive/Final TTS and TTRS exhaust valve/flap thread



## jimkamen (Nov 28, 2016)

There is *no pump*.
There is a vacuum reservoir with a check valve, fed by manifold vacuum.
There's an electronically controlled vacuum solenoid attached to the reservoir
which doles out vacuum to the vacuum actuator that actually drives the flapper 
valve. 
The ECU normally controls the signal to the vacuum solenoid, but
that wire can be interrupted manually (one form of flapper mod). 
When there's an open circuit on the signal wire, the solenoid is closed,
no vacuum goes to the actuator and a spring keeps the flapper open.
When the ECU pulls the solenoid circuit to ground (other side of
the solenoid is on 12v source) it opens the solenoid sending vacuum
to the actuator, closing the flapper valve. 
If you disconnect the vacuum line to the actuator then it creates
a vacuum leak which can, but rarely does, throw a code (same as
any small vacuum leak).
If you disconnect the ECU signal wire to the solenoid without
fooling the ECU with a 12v source and resistor, then it throws
a code saying it can't see the flapper solenoid.

Author: Daemon42


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## brittan (May 18, 2007)

jimkamen said:


> There is *no pump*.
> There is a vacuum reservoir with a check valve, fed by manifold vacuum.
> There's an electronically controlled vacuum solenoid attached to the reservoir
> which doles out vacuum to the vacuum actuator that actually drives the flapper
> ...


Well, if you want to believe that, that's fine.

The camshaft driven vacuum pump is on the RH side of the cylinder head as you look at the engine from the front.
It supplies the brake servo and the exhaust flap reservoir.

With no vacuum pump how do you think the vacuum in the reservoir is generated and replenished? 
It definitely will not be from the manifold on a TURBO CHARGED engine!!

The rest is more or less right but if you manually interrupt the wire to the solenoid (with a switch for instance) there is a continuity fault logged every time you operate the switch.

NB: when the solenoid goes from open to shut it also has to allow ambient pressure air into the downstream hose and flap actuator - otherwise the vacuum remains in that section of the system and the flap will not change position.


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## Danny1 (Sep 2, 2010)

Im still baffled why it matters at all to the OP tbh lol, there is a simple mod to have it open all the time, there are stainless systems if you want even more noise and then there is BCS stainless if you want a valved system with more noise and if you want the all singing all dancing one get the Armytrix.


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## xpoweruk (Feb 14, 2019)

I know this is an old post,but does anybody know the location of all the parts that operate the system ?


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## badger64 (Feb 17, 2019)

xpoweruk said:


> I know this is an old post,but does anybody know the location of all the parts that operate the system ?


for the ttrs the solonoid valve which activates the exhaust flap is located up behind the rear valance panel above the n/s tailpipe. follow the rubber vacuum hose from the flap actuator on tailpipe up to the plastic solonoid.


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## xpoweruk (Feb 14, 2019)

Where in the engine bay on a TTS does the hose go to get vacuum ?
My hose is just dangling free next to the noise generator on the UK passenger side of the engine bay.

I also have a vacuum leak causing P0171 code that I am struggling to locate


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