The BNR S4 version 4 turbocharger has a 3.5” inlet and works with a 3.5” or larger intake pipe. All the tuners like using an aftermarket boost control solenoid with a single barbed wastegate actuator. The S4’s point milled billet compressor wheel is rated for 53 lb/min air flow and is the smallest of the 71mm Garrett compressor wheels. This is by far the most popular turbocharger on the Mazdaspeed and the MPS market! Axillary methanol injection is needed to go higher than 370 WHP. This unit will do up to 480 WHP without sacrificing response. Here is what you get with the S4 turbocharger upgrade!