So, the question I have is, do stock cars with Turbo's have Bov's? My understanding is that they dont, thats what the wastgate is for. Bov's are just better performance wise for engine decceleration and such. I am going to be buying an 87 TII and was wondering if I bought an aftermarket Bov, if I need to make a hole for it in the intake and such. Thanks a bunch.

 

They do indeed have a BOV

 

They have bov's, they're just recirculated into the TID so theres no woosh noise.



And a bov and wastegate are two completely different things. A wastgate diverts exhaust gases away from the turbo to limit boost.

 

Exactly what Lee says.. wastegates divert the exhaust gases to control and limit boost levels and blow off valve or relief valve relieves air in the intercooler pipes when thethe throttle plates slam shut therefore it blow offs instead of returning in the compressor.. hence but causing compressor surge..

 

Mazda calls it the "Air Bypass Valve" and its considered part of the "Deceleration Control System". It sits close to the passenger-side fender, in a hose that connects the pressure side of the turbo with the TID, and has a vacuum line going to it.

 

Here is a shot of the stock S4 (left) and S5 (right) Bypass valves.

 

Sweet, thanks guys