BMW N20 Tuning

"All you need to know about tuning the BMW N20 engine!"

The BMW N20 have loads of potential and with the right sports upgrades like remaps, turbo improvements and camshafts you will definitely maximize your driving enjoyment.

Let us outline options for your N20 tuning and outline the premier mods that work.

History, Power & Specs of the Engine

It replaced the N53 / N52  and thanks to the turbocharger, it made similar power to the straight 6 predecessor. The Double VANOS and twin scroll turbocharger kept the car in the power band for most of the RPM range.

N20B16

  • 168 bhp @5,000 rpm 250 Nm 184 lbft @1,500-4,700 rpm

N20B20

  • 154 bhp @5,000 rpm 240 Nm 177 lbft @1,250-4,500 rpm
  • 181 bhp @5,000 rpm 270 Nm 199 lbft @1,250-4,500 rpm
  • 215 bhp @5,500 rpm 310 Nm 229 lbft @1,350-4,800 rpm
  • 241 bhp @5,000 rpm  350 Nm 258 lbft @1,250-4,800 rpm


Tuning the BMW N20 and best N20 performance parts.

Best N20 upgrades

The best N20 upgrades on an engine are typically the ones that give the biggest return for your cash.

We won't be swayed by popular N20 upgrades, they need to be cost effective.

Altering your N20 camshaft will make a dramatic difference to the engine engines power. Choosing a higher performance camshaft profile raises the engines power accordingly.

Fast road cams usually increase the torque over the rev range, you could sacrifice a little low end bhp but higher rpm power will be better.

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

A Motorsport and race cam will just annoy you whilst in heavy traffic.

You should ideally optimize your bhp range to your cars usage so for a car used daily stick with a fast road N20 cam

Some N20 engines respond better to extreme cam durations check your engine on a rolling road.

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

Extending exhaust or intake 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: Sports exhaust manifold, Fast road camshaft, Intake headers, drilled & smoothed airbox, Remaps/piggy back ECU, Panel air filters.

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

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

Review your options and then acquire your upgrades and set yourself a power target to avoid disappointment.

ECU mapping will help release the full potential of all the upgrades you've fitted to your N20.

(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 mileage will vary depending on the upgrades you've fitted and the condition of your engine.

Getting air into your N20 is the whole point to any performance tuning task.

Headers take the air during the suck phase from the filter and allow it to be sucked into the engine and mixed with fuel.

The bore size, shape and flow characteristics of the Plenum can make a noticeable improvement to fuel mixing and power on the N20.

I usually find plenum chambers are crying out for aftermarket parts, although a few OEM provide fairly well optimized plenum chambers.

Fitting big valve kits, doing some port work and head flowing will also improve bhp, and importantly will raise potential for an improved bhp 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 N20

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

When a car has forced induction tuning mods are going to make more power and you'll see that turbo engines are made using stronger components.

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

It is important to find these limitations and install stronger pistons, crank and engine components to cope with the power.

We've seen mechanics spending a loads of money on turbo charger upgrades on the N20 only to watch the whole thing catastrophically fail just after it's been completed.

Large turbo units commonly suffer a bottom end lag, and little turbo units spool up quickly but don't have the peak rpm power band gains.

We are pleased that the world of turbos is always moving on and we commonly find variable vane turbos, where the vane profile is altered according to speed to lower lag and increase top end performance.

Twin scroll turbos divert the exhaust flow into 2 channels and direct these at differently angled vanes in the turbo. They also help the scavenging effect of the engine.

It is common that there is a restriction in the air flow sensor AFM/MAF on these engines when considerably more air is being fed into the engine.

We note 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor limited torque at a much lower level.

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

Fuelling

You will need to ensure that the engine is not starved of fuel so will have to uprate the fuelling when you start going beyond 20% of a bhp and torque increase.It is important to over specify your injectors flow rate.

The rule of thumb is to add 20% capacity when specifying an injector, this allows for 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

4 Cylinder supercharged engines

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

Exhaust

You should look to improve your exhaust if the current exhaust is creating a flow problem.

On most factory exhausts you'll see your flow rate is fine 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 can help balance the flow of air through the engine.

But if the exhaust is too large, ie: over 2.5 inches bore, you will lose a great deal of the flow rate and end up sapping power and torque.

Usual exhaust restrictions can be located the filters installed, so adding a better flowing sports alternative is the answer. This keeps the car road legal and will flow much better due to it's higher internal surface area and design, so has the added benefit of keeping your car road legal. The alternative decat should be considered an off road only mod, as removing a catalyst is illegal in most territories and regions for road registered cars..

Weak spots Issues & problem areas on the N20

The N20 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.

Oil sludge builds up and can wreck the turbo and or oil pump. DONT IGNORE any rattles or buzzes or hums from the N20.

We should mention the class action lawsuit alleging timing chain guide failures due to a manufacturing defect.

Regular oil changes are vital on the N20, 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 N20 engine please join us in our friendly forum where you can discuss tuning options in more detail with our tuning articles to get a full grasp of the benefits and drawbacks of each modification.

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