BNR S4V4 Turbocharger Upgrade

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! Auxiliary fuel injection is needed to go higher than 370 WHP.  This unit will do up to 490 WHP without sacrificing response. Here is what you get with the S4 turbocharger upgrade!

• GT30 Turbine wheel
• 54mm/71mm Gen2 point milled billet compressor wheel (53 lbs/min flow rate)
• High Performance 360 thrust assembly
• Rear journal bearing oil deflector (Diverts oil away from the turbine seal)
• High Performance turbine seal
• VSR Balanced
• BNR T04B compressor housing .70 a/r (3.5” inlet, 2.25” extended outlet)
• BNR .72 a/r turbine housing with 27mm wastegate port
• Upgraded wastegate actuator (set at 15 psi)
• 5 Layer stainless MLS turbine inlet/outlet gaskets
• (9) M10 1.5 exhaust studs
• (9) M10 1.5 Stainless nuts/washers
• Extended stainless water line (firewall side)
• (4) 14mm copper washers
• (2) 12mm copper washers
• (2) Oil return gaskets
• year warranty!

BNR Supercars specializes in the Mazdaspeed3 and Mazdaspeed6 turbochargers. 

Peak numbers are not what we are into.  We like designing turbocharger upgrades that produce maximum under the curve power and torque.  It makes these cars much more responsive and fun to drive on the street.  When you get greedy and go for that peak number, it kills the bottom and mid-range torque.   No bottom end torque makes the engine not as responsive for autocross/road racing and in BNR's opinion not as fun to drive!

These engines are doing very well handling 400-450 WHP with the stock bottom end.  Most people looking for a reliable replacement over the stock smoking KO4 usually go for the S1 or S2 turbocharger models since a tune isn’t required.  If your car is fully bolted with high performance fuel pump internals we suggest an S3 with a tune.  Fully bolted with added methanol injection go with the S4 and a tune.   Stock engine internals, don’t even think about doing an S5 or S6!

*Divorced down pipes do not work with BNR turbocharger upgrades!  If they are used, the wastegate valves will not open properly causing extreme high boost problems!*

*Built engines need a custom oil supply line for turbocharger protection!  Click link for details!*

Mazdaspeed 3/6 Custom Oil supply line “Built engines only”

*S5 and S6 model turbochargers to cover the cost of the custom oil drain line! 

*Please note, turbos may ship directly from BNR, so please allow extra time for the turbo to be built and delivered.