DOC Race Top-Mount Single Precision Turbo Kit – BMW 335i / 335is / 135i (N54, RWD)

OVERVIEW

The DOC Race N54 top-mount kit converts the factory twin turbos to a single Precision (PTE) turbocharger on a one-piece T4 twin-scroll V-band manifold. DOC Race holds the N54 single-turbo record at 889 hp with this platform, and the manifold (redesigned 9/2020 as a one-piece unit) is proven well beyond 1,000 hp.

Boost is controlled by twin Turbosmart 40mm wastegates mounted low and away from exhaust heat, so springs can be swapped without pulling hot parts. A 2.5" aluminum charge pipe feeds the intercooler and a two-piece 3" stainless V-band downpipe connects to the factory exhaust location.

SPECS

• Precision turbo options: Gen2 ball bearing 5862 / 6062 / 6266 / 6466 / 6870, Gen1 journal bearing 5862 / 6266, Next Gen ball bearing 6266 / 6466 / 6870, or supply your own turbo
• DOC Race power ratings: 5862 – 640 hp; 6062 – 750 hp; 6266 – 800 hp; 6466 – 900 hp; 6870 – 1,100 hp
• One-piece stainless T4 twin-scroll V-band manifold, rated well beyond 1,000 hp
• 2 x Turbosmart 40mm external wastegates with 14 psi springs
• 3" stainless two-piece V-band downpipe to factory exhaust location
• 2.5" aluminum intercooler charge pipe
• Transmission option: MT or AT/DCT (same price)
• Rear-wheel-drive cars only — DOC Race does not offer an xDrive version
• Lead time: approximately 4 weeks; the turbo ships separately from Precision Turbo
• The price shown on the "supply my own turbo" option does not include a turbocharger.

PARTS INCLUDED

• Precision turbocharger (unless "supply my own turbo" is selected)
• 2 x Turbosmart 40mm wastegates with 14 psi springs
• DOC Race stainless one-piece T4 twin-scroll V-band manifold
• 3" stainless upper and lower downpipe with V-band clamps
• 2 x stainless wastegate dump tubes
• 2.5" aluminum intercooler charge pipe with silicone couplers and clamps
• 4" shorty air filter
• Stainless braided oil drain line and -4AN oil feed line kit
• Coolant block-offs, oil feed adapter fitting and CNC coolant pipe with hardware
• Coolant tank relocation bracket, hoses, barb fittings and clamps
• T4 turbo gasket, 6 x OEM-style doughnut gaskets, 4 x 10x1.25 studs and nuts
• Heat shield
• 10 ft silicone vacuum hose and 3 x vacuum tees
• DOC Race turbo blanket

TECH RESOURCES

Required Additional Parts

• Tuning (required) by an established N54 tuner: Burger Motorsports JB4 Tuner – N54, MHD Super License – N54.
• Upgraded fueling above ~550 hp: factory injectors support about 550 hp — Precision Raceworks / BMP N54 Port Injection Kit.
• Upgraded intercooler (recommended): Evolution Racewerks Competition FMIC – N54 or Mishimoto N54 / N55 Intercooler.
• Clutch for manual cars at higher power, e.g. XClutch Stage 2 (6-bolt) or XClutch Stage 2 (8-bolt).
• Replace during install (BMW OEM): 2 x 2-bolt exhaust gaskets 18307553603 and 1 x coolant pipe O-ring 11537545302.
• A MAC boost solenoid is not included and is only needed to control boost from a JB4 or similar device.

Installation

• Subframe removal is not required — the engine is raised about 2" and the one-piece manifold installs from above.
• The kit ships in two packages (DOC Race kit and the Precision turbo).
• DOC Race kit overview video: Video 1, Video 2, Video 3, Video 4.
• DOC Race does not publish an installation manual for this kit. Contact Speed Logic for install support.

VEHICLE APPLICATIONS