How do I mod my N55 to make BIG power?

The N55 engine, often overlooked in the BMW community, has the potential to rival the N54 and B58 when properly tuned. With the right fueling, turbo, and supporting mods, you can push your N55's horsepower from 300 to 600 or even 700+.

Why the N55 seems to have a bad rep compared to the B58:

The N55, especially depending on the generation you get, comes with some deficiencies that stop it from achieving the numbers you might want from your downpipe & tune.

• Fueling
  • The N55's HPFP(High-Pressure Fuel Pump) only flows at .837 cc/rev which isn't too far off the B58's HPFP at .897 cc/rev but because of the ease of sourcing and installing a TU HPFP, you can easily bring that up to 1.107 cc/rev which is over a 30% increase for both engines. The big issue there is that the B58tu pump does not fit on the n55 without cutting the fuel pump mounting base, which risks improper installation of the pump, leading to engine failure. Luckily, there are plenty of upgrade options on the market, such as Spool Performance, Dorch Engineering, Precision Raceworks, and Nostrum. These are available from Island Racewerks and will get your fueling exactly where you want it to be.
  • The Injectors are another known deficiency. There are plenty of upgrade options available now from various brands, or even swapping in a set of S63 injectors can work, too. You can find all of the current options on Island Racewerks.
  • The low-pressure fuel pump is also known to be weak and stop these cars from surpassing the 500whp mark. Brands like Precision Raceworks and Spool Performance make great upgrade options that are almost all plug-and-play. 
• Turbo
  • In stock form, the N55 turbo is not exactly a performer. The turbos included on both generations of the N55 are very small and don't offer a lot of performance outside of the stock tuning setup. There are a few known EWG cars making +480hp but it won't stay reliable. With today's aftermarket, there are so many good options available to people looking to up that power. Spool Performance, Shuenk, FrankenTurbo, Pure Turbos, The Turbo Engineers, Big Boost, and Speed Tech are all great choices that vary in "power : price" ratio. All of these are available for purchase through Island Racewerks. We are also certified installers of all of the products we carry, so you can rest assured that we will get your vehicle modified properly.
• Transmission
  • Even though the ZF transmissions found in most BMWs are known to be stout, the HP45 variant in the 335i in the F series and the HP26 in the E series can start to slip in the 500-600 tq range. They are only rated for about 450tq, but plenty have taken the abuse past it. The issue is that it's a ticking time bomb waiting to go. There are now options available to stop it from leaving you stranded: Interal upgrades or even direct swaps with other transmissions. Contact us today to figure out what's right for you!
• Engine Design
  • The N55 and the N54 are the only motors in the inline 6 lineup that are an open-deck design. This helps the motor cool more easily and lowers weight but sacrifices the strength of the cylinder walls. Both motors are also aluminum blocks, which can be another issue when pushing higher levels of boost. There are a few options to fix these concerns, such as closed deck conversion, which can be costly and usually requires your motor be taken to a machine and fabrication shop to have the conversion welded in. Another remedy is to epoxy the deck closed and drill out coolant jackets to let the motor still cool properly.
  • The N55 can suffer the same crankhub issues as the S55. Limited versions of the N55, like the ones found in the M235i and M2, came with a forged crank like its M version, the S55. Also, all EWG versions came with S55 rod bearings and forged connecting rods.
  • The head studs used in the N55 are known to give out around the 30 psi mark and will lift the head under high pressure. A known fix is to swap all the studs to 11mm studs, which includes drilling and threading 4 of the OEM spots.

There are still things to account for on the chassis side of your vehicle that, when upgraded, can only improve how your vehicle handles the power and puts it down. If you don't know where to start, we have experienced mechanics available for consultations to see what is right for you and in the price range you want to stick to. We also offer in-person installation in the Indianapolis area for an affordable price. N55's aren't the only BMWs we work on. We offer trustworthy work on any European vehicle.

Contact us today to make your dreams a reality!