BMW N45 Tuning

"All you need to know about tuning the BMW N45 engine!"

We were emailed us for more information on tuning and building a modified N45 and particularly which turbo upgrades work best, so we've put together this page which covers our go to modifications for this engine and what we feel are the greatest value modifications you can do.

The BMW N45 are fantastic to work on and with the best performance upgrades like ECU maps, turbo upgrades and camshafts you will definitely increase your driving experience.

We shall review N45 tuning and provide tips on the premier modifications.

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History of the N45 Engine

N45B16 2004-2011

  • 1,596 cc  114 bhp @ 6,000 rpm 111 lbft@ 4,300 rpm

N45B20S 2006

  • 1,997 cc 174 bhp@ 7,000 rpm 155 lbft @ 4,250 rpm


  • 2004–2011 E81/E87 116i
  • 2006–2011 E90/E91 316i


The N45 cc was raised to 2.0, for the World Touring Car Championship entry the E90 320si .The engine used DOHC camshafts and 16 valves and boasted a higher RPM when power could be extracted.

  • 2006 E90 320si

Tuning the BMW N45 and best N45 performance parts.

Best N45 mods

When talking about the best modifications for your N45 engine, we are going to focus on the mods that offer the best power gain for you money.

N45 Camshaft Upgrades

Sporty camshaft profiles work better at upper RPM range power so are more suited to petrol engines, than diesel ones. In most cases, you will see top end power benefits through performance camshafts on most engines.

Significant gains on the N45 can be made from camshaft upgrades. Altering the camshaft profile alters the intake and exhaust durations on the engine and can dramatically change the engine's power and power output.

Fast road cams normally raise the performance across the rev range, you could drop a little low down torque but the top end will be higher.

Motorsport cams, raise the top end band but as a result, the car will not idle smoothly and low end power nearly always suffers.

A Motorsport cam makes it harder when on the daily commute.

You should ideally match your torque band to the usage of your car so for a car used daily stick with a shorter duration N45 cam

Each engine responds differently due to the head and flow characteristics when camshafts are fitted depending on the camshaft being more extreme camshaft durations than others as unique due to manufacturing tolerances and quality variations so check your engine on a rolling road.

Best N45 Mods

The engine timing and fuelling also will make differences on the bhp gains you'll hit and you need to remember to remove any restrictions, which commonly occur when you raise the power.

A longer valve duration can alter the bhp range, and on most engines, there are some advantages to extending the intake or exhaust durations and valve lift.

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Best mods for your N45

  1. Upgrades to turbochargers and superchargers - Adding a turbocharger is the most significant way to raise the intake air supply, this means you are able to burn more fuel and make more power. Typically one of the most expensive mods it does provide the largest gains.
  2. Intake and Sports Exhausts - NB: on their own these mods won't ADD POWER in most cases, but they can help lift power after other mods by lessening the restrictive flow.
  3. Flywheel lightening - a reduced weight flwheel will improve the engines rev changes. But not always suitable for all N45 engines.
  4. Mapping - A remap gives the biggest gains compared to cost, aftermarket ECUs, and inline Tuning boxes are all alternatives.
  5. Flowing and porting the engine head - for larger gains, you will get better flow and make a more efficient engine if you do this to support your other mods.
  6. Fast road Camshafts are generally the biggest mechanical mod upgrade, but they must be fitted by someone who knows what they are doing and tracking one down can be a challenge but there might be a local firm to regrind a stock cam.

N45 Tuning Stages

Typical stage 1 mods often include: Intake manifolds, Fast road camshaft, Drilled & smoothed airbox, Sports exhaust header/manifold, Remaps/piggy back ECU, Panel air filters.

Typical stage 2 mods often include: Fast road cam, Ported and polished head, induction kit, Sports catalyst & performance exhaust, high flow fuel injectors, fuel pump upgrades.

Typical stage 3 mods often include: Engine balancing & blueprinting, Crank and Piston upgrades to alter compression, Adding or Upgrading forced induction (turbo/supercharger), Internal engine upgrades (head flowing porting/bigger valves), Twin charging conversions, Competition cam.

Plan your options and then find your mods and set yourself a power target to avoid disappointment.

ECU Mapping Improvements for the N45

ECU mapping should help to fully realize the full potential of all the mods you've fitted to your N45.

(Sometimes flashing the ECU is not an option, so an aftermarket ECU is the route to take, and most of these exceed the specs and performance of your factory ECU's but make sure it has knock protection and that you get it set up properly.) It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NA (naturally aspirated) engines, but power output will differ on the mods you've carried out and the condition of your engine.

Air Flow improvements on the N45

Feeding air into your N45 is vital to any performance tuning job. Air Intake manifolds carry the air during the suck phase from the air filter and allow it to be pulled into the engine cylinders with fuel for the squish phase.

Design and flow rate of the Intake can make a noticeable difference to to fuel atomisation on the N45.

We often see plenum chambers are crying out for aftermarket tuning parts, although some car makers provide well optimised plenum chambers.

Fitting big valve kits, getting 3 or 5 angle valve jobs and porting and head flowing will also raise torque, this will afford you an improved torque increase on other parts.

N45 Turbo upgrades

NA (naturally aspirated) engines need quite a lot of work when you add a turbo, so we have a separate guide to help you take into account the pros and cons of going this route on your N45

The more air you can get into an engine, the more fuel it can burn and uprating the induction with a turbocharger upgrade makes impressive power gains.

However you'll find engines will need better parts at higher power limits.We recommend you find these restrictions and fit better pistons and crank to cope with the power.

There are many mechanics spending a loads on turbo upgrades on the N45 only to suffer the humiliation of seeing the car catastrophically fail just after it's completed.

Bigger turbo units will usually experience low end lag, and smaller turbo units spool up more quickly but do not have the peak rpm engines power gains.

Thankfully the range of turbochargers is always developing and we are seeing variable vane turbochargers, allowing the vane angle is altered according to speed to lower lag and increase top end power.

Twin scroll turbochargers divert the exhaust gases into 2 channels and feed these at differently angled vanes in the turbocharger. They also increase the scavenging effect of the engine.

It is common that there's a limitation in the air flow sensor AFM/MAP on the N45 when loads more air is being pulled into the engine.

Going up you'll find 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor was restricting torque at a much lower level.

Adding a supercharger or additional turbo will make large performance gains, although more challenging to configure. We have this feature on twinchargers if you want to read more.

N45 Fuelling Upgrades

When you raise the power you will need to increase the fuel delivery.

More power needs more fuel. Fuel pressure boost valves raise the fuel pressure, can improve throttle response.We strongly recommend you over-specify your injector's flow rate which helps as they age, or the car performance increases or changes with different grades and qualities of fuel, with Ethanol based fuels requiring more supply to meet the air fuel ratios.

As a rule of thumb add another 20% when fitting an injector, which takes into account injector deterioration and allows a bit of spare capacity should the engine require more fuel.

We think this one is common sense, but you'll need to match your fuel injector to the type of fuel your car uses as well.

N45 Performance Exhausts

Only look to increase your exhaust if your current exhaust is creating a flow problem.

On most factory exhausts you should find that your flow rate is still ok even on modest power gains, but when you start pushing up the power levels you will need to get a better flowing exhaust.

Sports exhausts will certainly help air flow out of the engine but avoid an exhaust that is too large or you could restrict the flow rate. Generally speaking you should stick to around 1.5 to 2.5 inches for best results.

Typically exhaust restrictions are in the catalysts installed, so adding a higher flowing race aftermarket catalyst unlocks that lost power, and rather than doing an illegal decat, will keep the car road legal. Please note that performance catalysts and filters perform comparably to decat and have the added benefit of keeping your car street legal, as decat or catalyst removal is not a street legal modification.

Weak spots, Issues & problem areas on the N45

The N45 engines are not bad as far as reliability goes as long as they are well maintained.

Carbon build up in the head, particularly around the valves which will sap power or create flat spots, this is a larger issue on direct injection engines but should be looked out for on all engines. We have tips on removing carbon Avoid short journeys and use good quality fuel.

Service time oil changes are vital on the N45, and more importantly so when the car is tuned, and will help extend the life and reliability of the engine.

If you want to learn more, or just get feedback on Tuning your N45 engine please join us in our friendly forum where you can discuss N45 tuning options in more detail with our N45 owners. It would also be worth reading our unbiased BMW tuning articles to get insights into each modification and how effective they will be.

Please help us improve these tips by sending us your feedback in the comments box below.

We love to hear what our visitors have got up to and which parts work best for them on each model of car. We use your comments and feedback to improve the accuracy of these N45 tuning guides which get regular updates and revisions.

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