BMW N45 Tuning

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

The BMW N45 really good project engines and with the optimum modified parts like remaps, turbo improvements and camshafts you will substantially enhance your driving opportunities.

TorqueCars will review and look at N45 tuning and point out the best modifications.

History, Power & Specs of the Engine

The N45  DOHC, with VVT replaced the N40 and shares much with the N46 the original 1.6 engine was raised to 2.0 for homologation in the WTTC thanks mainly to the higher rev band and potential for tuning, making this an excellent choice for a tuning project.

N45B16 2004-2011

1,596 cc (97.4 cu in) 85 kW (114 bhp)  at 6,000 rpm 150 Nm (111 lbft)  at 4,300 rpm

N45B20S 2006

1,997 cc (121.9 cu in) 130 kW (174 bhp)  at 7,000 rpm 210 Nm (155 lbft)  at 4,250 rpm

Tuning the BMW N45 and best N45 performance parts.

Best N45 parts

When talking about the optimum modifications for your N45 engine, we are going to focus on the parts that give the biggest return for your cash.

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 engines power and power output.

Fast road camshafts tend to bump the performance across the rpm range, you could drop a little low end power but your higher rpm power will improve.

Competition camshafts, bump the higher rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

For a typical daily driver must carefully try to optimize your torque band to your typical driving style.

You'll never find a N45 Competition camshaft is a pleasure to live with when driving in heavy traffic. The low end idle will be very lumpy and irregular, so something you would notice on a track when you drive in the upper third of the rpm band, but on roads this is a serious issue and we've heard from lots of drivers lamenting their decision to add an extreme competition cam profile to their engine.

Some N45 engines respond better to extreme cam durations check your engine on a rolling road.

The map and fuel pump and injectors also have an effect on the bhp gains you'll achieve.

Altering valve durations can alter the bhp band and on most engines the exhaust and intake durations do not need to match, although most cams and tuners use matched pairs there are some advantages to extending the intake or exhaust durations.

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

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

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

 

The N45 engine blocks respond well to upgrades and we see that there is a lot of upgrades and performance parts around.

 

ECU flashing helps release the full potential of all the tuning parts you've done to your N45.

(In some cases, as the factory ECU is locked flashing is not an option, so an aftermarket ECU is the route to take, and many of these will outperform factory ECU's but make sure it has knock protection and that you get it setup properly.)

It will usually give you around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but your results usually depend much on the tuning parts you've carried out and the condition of your engine.

Pulling more air and fuel into your N45 is the whole point to any tuning job.

Intake manifold carry the air from the air filter and allow it to be drawn into the engine cylinders.

The shape and flow characteristics of the Air Intake manifolds can make a substantial effect on to fuel atomisation and engine efficiency on the N45.

Commonly we find the intake headers are crying out for aftermarket parts, although some car makers provide decently flowing intake headers.

Fitting big valve kits, doing some N45 port enlargement and head flowing will also increase performance, this will afford you a better performance increase on other parts.

Turbo upgrades

NASP 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.

When a car is fitted with a turbo mods are going to net you a larger power gain and turbocharged engines are built using uprated components.

There are tuning limits for every engine, with some being very over engineered and some only just able to handle stock power

It is important to find these restrictions and install forged components to survive the power.

We see many people spending a lot of money on turbocharger upgrades on the N45 only to suffer the humiliation of seeing the engine block go up in smoke soon after it's completed.

Big capacity turbos tend to experience no power at low rpm, and low capacity turbos spool up really quickly but won't have the peak end engines power gains.

Thanks to new tech the market of turbo units is always improving and we now see variable vane turbo units, where the vane profile is altered according to speed to lower lag and increase top end bhp.

Twin scroll turbo units divert the exhaust flow into a couple of channels and flow these at differently profiled vanes in the turbo. They also improve the scavenging effect of the engine.

You'll commonly see there's a limitation in the air flow sensor MAP/MAF/AFM on the N45 when loads more air is being fed into the engine.

You'll see that 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor sapped torque at a much lower level.

Adding a supercharger or additional turbo will make large bhp gains, although more complex to install. We have this in depth look at twinchargers if you want to read more.

N45B16 N45B20S Fuelling

Don't omit to improve the fuel delivery when you are increasing the power - it makes the car more thirsty. It makes sense to be generous with your injectors flow rate.

 

As a rule of thumb add 20% when specifying an injector, which takes into account injector deterioration and allows some 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.

All the following flywheel power targets will assume an injector duty cycle of 80% and a base of 58psi of fuel pressure at idle.

4 Cylinder turbocharged engines

  • 58 PSI 340cc/min 200hp
  • 58 PSI 511cc/min 300hp
  • 58 PSI 682cc/min 400hp

4 Cylinder NASP engines

  • 58 PSI 285cc/min 200hp

4 Cylinder supercharged engines

  • 58 PSI 312cc/min 200hp
  • 58 PSI 468cc/min 300hp
  • 58 PSI 625cc/min 400hp

Exhaust

You may need to increase your exhaust if your current exhaust is creating a restriction.

On most factory exhausts you should find that the exhaust flow rate is 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 balance the flow of air through the engine.

But if the exhaust is too big, ie: it's over 2.5 inches bore, you will lose much of the exhaust flow rate and end up sapping power and torque.

Usual exhaust restrictions can be located the catalyst installed, so adding a faster flowing performance catalyst removes the restriction. We note that performance cats perform similarly to decats and have the added benefit of keeping your car street legal, as decats or catalyst removal is illegal in most territories for road going cars.

Weak spots, Issues & problem areas on the N45B16 N45B20S

The N45 engines are generally reliable and solid units, as long as you follow the manufacturers service schedules, and use a good quality oil to ensure longevity. Few problems should happen as long as they are regularly serviced and 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 build up.

Some of our members have had issues with flat spots or glitches after applying mods and upgrades or tuning, this is not usually related to this engines design, so instead see our article on diagnosing flat spots and problems after tuning which should help you get the bottom of this issue.

Regular oil changes are vital on the N45, especially when tuned and will help extend the life and reliability of the engine.

If you would like to know more, or just get some friendly advice on Tuning your N45 engine please join us in our friendly forum where you can discuss tuning options in more detail with our N45 owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

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 tuning parts work best for you on your car. Which helps us keep our guides and tips up to date helping others with their modified car projects. Your feedback and comments are used to keep this page up to date, and help improve the accuracy of these N45 articles which are continually updated.

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