bingoboy

ok i recently got a racing beat header and presilencer used but in pretty good condition. i have an S5 car, but the presilencer was from an s4 car.

s4 one looks like this:


the s5 one looks like this:


the s4 one has that extra piece of "backpressure sensing tube necessary for proper operation of the 6-port actuator valves" which should be unneccesary on an S5 car since the extra ports are driven by the airpump and not backpressure right?

well i got under there to look at the setup and there is a tube coming down that looks like its connector and placing would exactly fit the s4 presilencer backpressure tube. is that tube just for pumping air into the cats or does it do something else. i blocked off the piece on the presilencer but i'm second guessing myself now that i've seen the connector that runs to the primary cat. can anyone shed some light on this issue for me?

thanks,
scott

Icemark

That factory tube is a two way thing one the S4 cars, but one way for the S5 cars.

On the S4 yes it does use the backpressure to activate the 5th/6th ports, as well as it is used to pump air into the cat.

On the S5 it is only used to pump air into the cat, to keep the cat from overheating and lower emissions.

bingoboy

thanks Icemark.

Project84

I bought one of those last month. It comes with a block off plate for the Air Control Valve. You hook the stock tube to the presilencer and exhaust will flow through the presilencer, through the tube, and move the aux ports. The air pump and ACV can be tossed out. The instructions for the S5 says to keep the air pump and ACV cause the ACV and the way it ports air is a little different.