I have not measured it, but I do have some information.

I only run a 2psi wastegate spring, and rely on the boost controller (on board air tank) pressure into the top side of the gate to make the boost. Basically it requires 1psi of gate pressure, to make 1psi of boost. If the backpressure was at 53psi, it would be blowing that 2psi gate spring open for sure. Also, the car does not like RPM regardless of boost pressure. Even at 10 or 15psi it doesn't like RPM (ET slows down if you shift it higher).

But in principal, I do agree any combo can benefit from lower backpressure. 100% agree with that. But it's not the end all, be all, of a combo.


I would think a S480 combo (80/88) at 850hp goal is a great choice for the original poster. 80mm compressor will make 850 easily, It will spool relatively quick, and the China Knock off versions can be had for $750 or so in billet wheel form. I can't see doubling the complexity and cost with Twins being worth it in a build like that.