Hi, guys
Got the capristo hiflow cat and muffler installed today.
Factory exhaust has no valve control so the exhaust note changes when you press the button, does it come from speaker or something else?

 

Has to do with fuel mapping I believe.

 

Exactly. Fuel mapping is different on sport and support plus than normal. The difference is most magnified if you have catless exhaust. During my ride in the car with Tubi catless before deciding to buy it on normal there was no popping or backfiring. Of course in sport and sport plus at times it sounded like rifle shots going off you let off the throttle and suddenly the popping and backfiring is loud

 

This is my experience as well, exhaust almost sounds like it's valved in different modes. I have a catless setup.

 

There is a "Sound Symposer" on our cars, which is a sound port that opens between the engine compartment and the cabin in certain situations to let sound through.

http://rennlist.com/forums/991-turbo...d-sympose.html

 

Turbines pitch/angle are changed on the variable geometry turbos. This is how they allow for faster spool and over boost.

Mike