How are the BNR 400+ horsepower twin turbochargers from the RX-7 Store for the Mazda RX-7 FD?

The BNR twin turbochargers (commonly referred to as BNR Stage 3s) are highly regarded as a reliable, direct-fit upgrade for the Mazda RX-7 FD. They are an excellent choice if you want to retain the factory sequential system, maintain fast low-end spool response, and reach the 400+ rear-wheel horsepower (whp) mark without stepping up to a single turbo conversion.

Performance Characteristics These turbos feature an upgraded bearing section with larger, custom-spec GT28 (or T25) cartridges, which are fitted into precisely machined factory compressor and turbine housings ⁷. This setup yields fantastic street response for powering out of corners, with the ability to achieve 1 bar of boost (about 14.5 psi) under 2,000 RPM ⁷. With a proper engine porting and supporting modifications, they can make a solid 400 to 420 whp ³.

Installation & Fitment Details Difficulty: Moderate to Hard

While generally considered a plug-and-play setup, the upgraded center cartridges make the BNR turbos slightly longer than stock, which requires a few minor installation adjustments:

• Oil & Coolant Lines: The factory metal lines need to be re-clocked and slightly bent outward by about 5-10 degrees to mate properly. It is recommended to place the end of the line in a vise and bend it very slowly, testing the fit frequently so you do not over-bend or crack the hardline. You will reuse the stock banjo bolts and crush washers ⁷.
• Y-Pipe: BNR lengthens the front half of the Y-pipe to account for the longer turbo footprint by cutting the O-ring flange and welding in a short piece of aluminum tubing. The back half of the Y-pipe with the charge control valve is identical to stock ⁷.
• Intake & Exhaust: The exhaust downpipe, manifold, and gaskets remain completely stock. Because the intake opening on the compressor housing is machined larger, it is recommended to open up the stock gasket and turbo inlet pipes to match the larger diameter for maximum airflow ⁷.

To safely run this setup and achieve the 400+ horsepower goal, you will need a standalone ECU and proper tuning, along with an upgraded fuel system to support the higher airflow ¹.