does the s4 turbo have a triangular inlet?
does the s5 turbo have a circular inlet?
are the rx-7's the only cars with a ht18 turbo?

 

Umm, if you talking about the actual inducer to the compressor side of the turbo, both S4 and 5's are round in fact they're exactly the same compressor, only thing different is the exhaust housing's.....

 

Don't ALL turbochargers have a round inlet and round discharge on the compressor?

The only thing that "triangular" rings a bell about is the shape of the throttle body - triangular shape with 3 round valves instead of 1 large single one.

 

hahaha well yeah i've been racking my brain since I saw this post trying to think if i've ever seen a differently shaped turbo, but no, I havn't