I've done the swap along with a modified S5 engine a while ago. But the dilema is in order for it to work I had to block off the BACV and its intake hose. Someone told me that the S4 BACV (bypass air control valve) works on different volatage than the S3. Since hearing that I've never tried to correctly hook it up.

Question to all of you is: Has anyone who has successfully swapped to the s4 upper and lower intakes got the BACV to work??? If so, how? My idle is surging and I just was interested if someone got it to work. (I've ruled out TPS and 60% sure its not an intake leak.)

Any help is greatly appriciated. Thanks.

 

I don't know of anyone that has gotten it to work.
However you could mount the stock Se BACV if you grinded away at the side of the intake plenum enough for the Se bacv to attach or make a adapter plate to extend the BACV away from the plenum and use longer bolts.

 

true I guess I could always make a pipe for the coolant to pass through too since thats how the throttle body gets it on the S4..hmmm

 

On that S4 piping. The only reason they ran it thru the BACV is for simplicity reasons. It was so they did not have to make another special hose. The coolant going thru the nipples on the S4 BACV has no effect on the operation of the BACV.