Hey guys. I know the S4 operates the 5th and 6th ports off of the exhaust velocity, and that modifying your exhaust can cause the ports to not open or not function properly.


my question is, I saw racing beat has a cat replacement pipe that still lets the ports open properly, is there anyway I can fabricate my own cat replacement pipe that will do the same? ( I reallly dont want to spend 300 bucks on a piece of metal I can make for 50)


Any information on diameter, etc?

 

Modify the air pump to the ACV for the actuation like the S5.

 

Exhaust pressure, not velocity.

Correct, any reduction in exhaust backpressure will cause the ports to open later than they're supposed to. That includes any aftermarket or custom exhaust with a connection for the actuators. You're much better off mimicking the S5 set-up using an air pump, solenoid valve and rpm switch.