N55 Turbo Upgrade: Boost Your BMW's Performance

If you own a BMW powered by the N55 engine, you know it offers great potential for increased horsepower and torque. The 3.0L twin-scroll single turbo straight-6 came stock on many BMW models from 2009-2016, including popular cars like the 335i, 435i, 535i and others.

While the N55 makes 300-335 horsepower from the factory, there’s a lot more power to be unlocked with upgrades. And one of the best ways to dramatically increase N55 performance is by installing a larger turbocharger.

But there are some key questions you need answered when planning an N55 turbo upgrade:

What size turbo should you choose?
Do you need other supporting modifications?
How much power will it make?
And what is the total cost?

This complete guide to upgrading the turbo on your BMW N55 engine will walk you through everything you need to know. You’ll learn about:

The best turbo kits for the N55
Supporting mods you’ll need
Realistic power goals
Total upgrade costs
Pro tips for installation

By the end let’s boost your BMW!

Why Upgrade the N55 Turbo?

Before jumping in, let’s quickly go over why you may want to upgrade your turbo in the first place. Some key benefits include:

Dramatically increased horsepower – Larger turbochargers can help you easily achieve over 400, 500, or even 600+ wheel horsepower depending on setup. The stock N55 turbos max out around 300-350 hp.
More torque – Big turbo kits develop huge increases in torque across the entire RPM range. Expect torque increases of 100 lb-ft or more.
Improved throttle response – Reduced turbo lag from larger turbos that spool faster. Makes the engine feel more responsive.
Higher top-end power – Big single turbo kits extend the power band to redline for increased high RPM power.
Customizable power goals – Can tailor the turbo setup to your goals from mild to wild.
Retain drivability – With the right supporting mods, big turbo N55 builds can retain smooth day-to-day drivability.

So if you’re looking to really wake up your N55, a turbo upgrade should definitely be on your radar. The additional power transforms the stock driving experience.

Now let’s get into the details on planning your own turbo upgrade.

Best Turbo Kits for the N55

The first decision is choosing the right turbocharger for your N55 build. There are a few respected companies making turbo kits specially designed for the N55 engine.

Here are some of the most popular options:

Pure Turbo N55 Turbo Kit

One of the best choices for a complete turbo upgrade is Pure Turbo’s N55 Turbo Kit.

Key specs:

Ball bearing twin scroll turbocharger
Supports up to 500 wheel horsepower
Direct replacement for stock twin turbos
Tial external wastegates
Quality Tial BOVs
All hardware and gaskets included

Pure Turbo offers their kit in different upgrade stages depending on your power goals:

Stage 1 is a great option for mild power gains up to 350-400 wheel horsepower. It comes with a quality ball bearing turbo that matches the stock twin turbo output.

Stage 2 bumps up to a larger 61mm twin scroll turbo capable of up to 450-500 wheel horsepower. This is the most popular option for big power builds.

And for those looking for even more power, their Stage 3 kit upgrades to a 64mm turbo that can support over 500 wheel horsepower.

The Pure Turbo kits are great because they offer an upgrade path. You can start with Stage 1 and later upgrade to Stage 2 or 3 by just purchasing a larger turbo.

It’s a complete package including the turbos, wastegates, blow off valves, adapters, gaskets, and all hardware needed. The only thing left is to get supporting engine mods and a tune.

Garrett Turbo Upgrade

Another good option is upgrading to a larger Garrett Turbocharger. Garrett makes a direct bolt-on replacement turbo for the N55 that can support around 400 wheel horsepower.

It offers an economical upgrade over stock with the convenience of direct fitment. The Garrett turbo uses the stock N55 twin-scroll turbo housings for easy installation.

The advantage of the Garrett option is cost. But it may require custom tuning and doesn’t offer higher upgrade stages. Overall it’s a good choice for a mild power increase on a budget.

Borg Warner Turbo

For big power goals over 500-600+ wheel horsepower, the Borg Warner EFR Series Turbo is a popular option.

Borg Warner makes an EFR replacement turbo for the N55 capable of supporting up to 650 wheel horsepower. It features their advanced Gamma Ti turbine wheels and comes with all hardware for installation.

It’s one of the more expensive options but can support big power if that’s your goal. The Borg Warner EFR matches the stock N55 twin scroll exhaust housing. So it bolts up to the stock exhaust manifold.

Downsides are it may require custom tuning and doesn’t offer lower upgrade stages. But for big single turbo builds, the Borg Warner EFR is hard to beat.

Other N55 Turbo Options

There are a few other notable turbo options including:

Precision Turbo: Various twin turbo and single turbo options from mild Stage 1 kits to extreme race specs.
G Series Single Turbo: G30 and G series Garrett single turbo kits popular for big power N55 builds. Requires more custom fabrication.
VF Engineering: Custom turbo solutions using Garrett turbos sized to your goals.

Supporting Modifications

Bolting on a bigger turbo is just the first step. To safely achieve your horsepower goals and ensure reliability, supporting modifications are required.

Let’s go over the main supporting upgrades you’ll need for an N55 turbo kit.

Fuel System Upgrades

More power requires more fuel. So fuel system upgrades are crucial to prevent lean conditions and detonation.

Upgrades like:

Large fuel injectors – Must match the power goals of your build. Injector Dynamics and Bosch are popular options. Expect to need 550cc, 630cc, or larger injectors.
Fuel pumps – Walbro makes drop-in replacement pumps capable of supplying adequate fuel flow for big turbo builds. Consider their 485L/hr pump as a minimum.
Ethanol content sensor – To take advantage of E85’s cooling effects and added octane for forced induction engines, you’ll need this sensor. Allows custom tuning for any ethanol blend.
Fuel pressure regulator – A FPR helps stabilize fuel pressure as power increases. Aeromotive makes a popular adjustable FPR.

With supporting fuel mods, you’ll be able to maximize timing and power output safely.

Intake Upgrades

More airflow is required to match the turbo’s increased output. Intake upgrades like:

Silicone intake piping – Replace the factory plastic intake tubes with larger diameter silicone piping. Improves airflow.
Intercooler – A larger efficient intercooler reduces intake air temperatures. CPE and Wagner make good affordable options.
Intake manifold – High flowing intake manifolds like the VRSF intake elbow remove restrictions.
Throttle body – BMWPerformance offers a 90mm throttle body that bolsters airflow over stock.

With these intake upgrades, you’ll be feeding that big turbo plenty of cool, dense air.

Exhaust Modifications

Improving exhaust flow helps the turbo spool faster and reduces backpressure. Consider:

Downpipe – Replace restrictive stock downpipe with a larger 3 inch downpipe to reduce backpressure.
Midpipe – Optionally upgrade to 3 inch midpipe for further flow gains.
Catback exhaust – Improves high RPM flow. Look for a 3 inch exhaust with high flowing mufflers or resonators. Popular options are Remus, Invidia, and Ark exhausts.

Many N55 turbo kits come with downpipes so you may only need a new mid pipe and catback. The full exhaust will help the turbo spool fast and make all that extra power.

Engine Internal Reinforcement

For big turbo builds aiming for 500+ horsepower, upgrading engine internals is recommended.

Potential upgrades include:

Pistons – Forged pistons help handle added boost pressures and heat. CP-Carrillo and Manley are respected brands.
Connecting rods – Stronger forged H-beam rods provide added reliability for 500+ hp builds.
Head studs – Improves clamping force to prevent head gasket issues under boost. ARP head studs are commonly used.
Main studs – Can install main studs for the crank if aiming for 600+ wheel horsepower. Extra clamping security.

Internal upgrades are absolutely necessary once you start approaching the 600+ wheel horsepower mark. They give you peace of mind when pushing the N55 to its limits.

Proper Tuning

Dialing in the right custom tune on your upgraded N55 is equally important. A proper tune will maximize your turbo kit’s power gains while optimizing drivability and safety.

You have two main options:

Protune – Go to a reputable shop with a chassis dyno to get your N55 protuned for your setup. Offers maximum gains.
Remote tuning – There are remote tuning shops that can email tunes loaded right to your car. MHD and Bootmod3 are popular.

Avoid cheap ready-made OTS tunes. Get a custom protune or etune specifically tailored for your mods and fuel type. This will unlock the full potential of the upgraded turbo kit safely.

Proper tuning is crucial – don’t neglect it and risk engine damage or leave power on the table.

Realistic Power Goals

Now for the fun part – estimating the horsepower and torque gains you can expect from your N55 turbo upgrade.

Of course final dyno verified results will depend on your specific setup and tune. But here are some general power estimates:

Stock N55 – Around 300-335 hp and 300-350 lb-ft torque
Stage 1 Turbo Kits – +50-100 hp over stock. So around 350-400 whp.
Stage 2 Kits – +100-150 hp over stock. Results in 400-450 whp.
Stage 3 Kits – +150-200+ hp over stock. So 450-500+ whp.
Big Single Kits – Can achieve over 500-600+ whp with built engine and supporting mods.

Just upgrading to a Stage 1 turbo kit and tune can put down +50-100 more horsepower to the wheels which is quite noticeable.

The Stage 2 and 3 kits with supporting mods can take things to the next level with up to 150-200 more horsepower. This will completely transform the acceleration and power band.

And for those looking to join the 500+ whp club, big single turbo kits make it possible. Just be ready to build the engine and drivetrain to handle that kind of power.

So choose your turbo kit based on your budget and power goals. From mild to wild, the N55 engine can handle it!

Cost Breakdown of Turbo Upgrades

Let’s do a quick cost breakdown of what to budget for your N55 turbo upgrade project:

Turbocharger Kit

Stage 1 Kit: Around $2,000-$2,500
Stage 2 Kit: Around $2,500-$3,000
Stage 3 Kit: Around $3,000-$3,500
Big Single Kit: $3,000-$4,500

Supporting Mods

Fuel upgrades: $1,000-$1,500
Intake upgrades: $500-$1,000
Exhaust work: $500-$1,000
Engine internals (if going big power): $2,000+

Installation Costs

Basic install labor: Around $500-$1,000
More complex install: $1,000-$1,500

Dyno Tuning

Local Protune: $500-$800
Etune: Around $300-$500

Total Costs

Stage 1 Build: Around $3,000-$4,000
Stage 2 Build: Around $4,000-$5,500
Stage 3 Build: $5,000-$7,000
500+ HP Build: $7,000-$10,000+

Keep in mind costs will vary based on your particular setup. But this gives you a rough idea of budgeting.

The stage 1 kits offer great bang for buck. Going bigger adds cost for supporting mods and engine work. Either way, you get huge horsepower-per-dollar value from an N55 turbo upgrade.

Pro Tips for Installation

Here are some tips for smooth turbo kit installation:

Use a reputable BMW performance shop – Have a shop experienced with BMW turbo swaps do the install. Worth the money.
Replace old gaskets – It’s cheap insurance to install new gaskets on things like the oil filter housing, valve covers, etc during install.
Take your time – Don’t rush the installation. Have the shop properly torque all bolts to OEM specs.
Do install over multiple days – Big turbo installs take 10-20 hours. Splitting it between multiple days reduces mistakes.
Address any leaks – Fix any existing oil leaks, boost leaks, vacuum leaks, etc during the install to prevent future issues.
Triple check tightness – Have the shop verify tightness on all clamps, connections, bolts after install to prevent leaks.
Do break-in drive – After install, do an easy break-in drive keeping RPMs low to seat the turbo. Then send it.

Take your time and use a reputable shop for a headache-free install. Do it right the first time to max out that new turbo!

Boost Your N55 with a Turbo Upgrade!

Upgrading the turbocharger on your BMW N55 engine is one of the most rewarding mods you can do. The massive increase in power and torque will completely transform your car.

This complete guide armed you with everything you need to know to successfully plan out your own N55 turbo upgrade including:

The best turbocharger options
Supporting modifications required
Estimated power gains
Total project costs
Pro tips for installation

Now you can upgrade your turbo and achieve your horsepower goals whether it’s 400, 500 or even 600+ wheel horsepower!

So use this resource to plan out your perfect N55 turbo kit, get your supporting mods in order, and look forward to the huge power gains. Your turbo BMW will become a whole new beast!