BMW N54 Parts: 135i, 335i & 1M Reliability, Then Power

The N54 is the twin-turbo 3.0-liter six in the 135i, 335i, 335is, 535i and 1M. It's one of the easiest BMW engines to make power with, but it's also old now, and a lot of its factory plastic and rubber parts are past their best. Our advice on any N54: fix the known weak points first, then tune. Most of the reliability parts also help once you add boost, so nothing here is wasted.

How the N54 makes boost

From the air filter to the exhaust:

1. Intake: the airbox feeds two turbo inlet pipes, one per turbo.
2. Two small turbos, each feeding three cylinders, with wastegates that control boost.
3. Charge piping: boost runs through a front-mount intercooler, then the charge pipe to the throttle body.
4. Diverter valves release boost when you lift off the throttle.
5. Downpipes: one per turbo, with the main catalysts.
6. Fuel: a mechanical high-pressure fuel pump (HPFP) on the engine feeds the direct injectors. An in-tank low-pressure pump feeds the HPFP.

Step 1: reliability parts

Charge pipe. The factory plastic charge pipe is a known N54 failure point. It cracks, usually at the worst moment. Replace it on every N54, tuned or not.

• FTP super charge pipe kit: the charge pipe plus the air induction pipe, with the clips and seals.
• Mishimoto charge pipe: a direct replacement for the plastic pipe.
• CTS charge pipe: built to keep the factory diverter valve.
• MMX charge pipe kit: comes with everything needed for the install.
• 535i owners: the E60 uses its own FTP 535i charge pipe.

Diverter valves. The factory diverter valves wear out and leak boost, especially once the car is tuned. The Turbosmart Kompact dual-port kit bolts in where the factory valves were. If you'd rather run a blow-off valve, the Active Autowerke BOV kit with charge pipe does both jobs in one.

Turbo inlets. The factory rubber inlets age and split. VTT silicone inlets replace them with wire-reinforced silicone.

Wastegate rattle. Worn wastegate hardware rattles and can make boost control less precise. The VTT wastegate repair kit fixes the hardware without replacing turbos that are otherwise fine.

Crankcase ventilation. Oil vapor from the crankcase ends up in the intake and on the intake valves.

• FTP PCV valve or VTT billet PCV cover and valve: replace the tired factory PCV parts.
• CTS catch can kit or FTP catch tank: catch oil before it reaches the intake.

Ignition. Fresh coils and plugs fix most misfires. Try Mishimoto ignition coils with Dinan iridium plugs. Tuned cars need plugs replaced more often.

Step 2: cooling

The stock intercooler heat-soaks quickly once boost goes up, and N54s run hot in a Texas summer.

• CTS direct-fit FMIC: a direct-fit front-mount intercooler for the 135i and E9X 335i.
• Mishimoto performance intercooler: another bolt-in option.
• CSF radiator (manual cars) or Mishimoto aluminum radiator, which also comes in an automatic version.
• Mishimoto racing thermostat and an oil thermostat like the MMX low oil temperature thermostat: help hold coolant and oil temperature down.

Step 3: tune and bolt-ons

With the weak points fixed, the tune is where most of the power is.

• COBB Accessport: a handheld that flashes the ECU and lets you monitor the car.
• Active Autowerke N54 software: a flash tune. It ships with an off-road-use-only waiver you have to sign.
• Intake: the CTS intake kit replaces the factory airbox. A COBB high-flow filter is the simple option.

Downpipes replace the factory downpipes and their catalysts, and they need a tune. The CTS cast downpipe set fits rear-wheel-drive 135i and 335i cars only. Catless downpipes are for off-road and competition use only, so check whether a downpipe keeps a catalyst before you order, and ask us if your state inspects emissions.

Step 4: fuel

More boost needs more fuel, and the N54's fuel system is the next limit. Every part here needs a tune set up for it.

• Low-pressure side: the DeatschWerks dual-pump module or the PFS bucketless single-shot pump supply more fuel from the tank.
• High-pressure side: the Spool Helix overdrive unit and the PFS POD make the mechanical HPFP spin faster for more flow.
• Ethanol: the Spool wireless ethanol analyzer shows ethanol content and fuel temperature on your phone.

Step 5: turbos and clutch

When the stock turbos run out, upgraded stock-location twins keep the factory layout.

• Pure Turbos Stage 1: a direct-fit upgrade for N54 cars.
• VTT Stage 1 or VTT GC Lite 2.0: all-new stock-location twins.
• TTE500: an entry-level hybrid upgrade.
• Use a VTT installation kit so every seal is new.

The stock clutch on manual cars slips once torque goes up. The ACT heavy-duty street clutch suits a tuned daily. The XClutch Stage 1 is another street option. The DKM twin-disc kit is for big-turbo cars.

What we'd do

• Daily driver: charge pipe, diverter valves, inlets, PCV, coils and plugs. Add a tune only once those are done.
• Weekend car: all of the above, plus an intercooler, a radiator and a tune.
• Tuned car chasing power: everything above, then the low-pressure pump, an HPFP upgrade and ethanol, then turbos and a clutch.

See every part that fits on the N54 page, or jump to charge pipes and intercoolers, turbos and diverter valves, fuel and engine, cooling and intakes.