Exhaust valve on Granturismo S query(mc shift)

ChrissGT

Member
Messages
341
Since we now know that there are internal actuators in the 4.2 back boxes that open up with exhaust pressure, I wonder if these invariably seize up, since there's going to be no lubrication in there.
Eb

I got a rattle in my 4.2 back box after installing a x-pipe. Guess the flow was a bit too much for the old thing to handle. I did get it cut open, but not to see what the source of the rattle was. Although there is not really an actuator that can rust solid. It's just a spring valve that open/closed based on air pressure.

If I ever find the time and think about it I will have a look, still have it lying around somewhere.
 

Ebenezer

Member
Messages
4,392
I got a rattle in my 4.2 back box after installing a x-pipe. Guess the flow was a bit too much for the old thing to handle. I did get it cut open, but not to see what the source of the rattle was. Although there is not really an actuator that can rust solid. It's just a spring valve that open/closed based on air pressure.

If I ever find the time and think about it I will have a look, still have it lying around somewhere.
Hi.
So you just removed the valve so exhaust is going to exit out of both tail pipes?
My understanding is that when the valve is closed the exhaust gas is routed through the sound deadening route and escapes though the inner of the twin pipes. When the valve is open the exhaust is less restricted and exits through the outer pipes.
Eb
 
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ChrissGT

Member
Messages
341
I installed valved mufflers. Im no expert in airflow. But it seems to always take the path of least resistance. So i do think when you are on full throttle the back pressure opens the valve and the exhaust air will go primarly through the unrestricted pipe.
Hence there was not a whole lot of difference between my 4.2 and the 4.7 valved when going full throttle.