Tuning the BMW N45B16 N45B20S

"Comprehensive guide to performance tuning the BMW N45B16 N45B20S engine!"

We often are getting messages requesting information on the best tips for N45B16 N45B20S mods that work. So let us look into BMW N45B16 N45B20S upgrades and outline the best modifications on this great engine and point out some potential pitfalls along the way.

The BMW N45B16 N45B20S are fantastic to work on and with the optimum sports parts like remapping, turbo upgrades and camshafts you will enhance your driving experience.

Let us review N45B16 N45B20S tuning and show the premier mods that work.

The best N45B16 N45B20S tuning parts on an engine are in our opinion the ones that give the biggest return for your cash.

We won't be swayed by popular N45B16 N45B20S tuning parts, they need to be cost effective.

Altering your N45B16 N45B20S camshaft will make a dramatic difference to the engine engines power. Choosing a higher performance camshaft profile raises the engines power accordingly.

NB: Fast road camshafts normally bump the power over the rev band, you could sacrifice a little bottom end bhp but your higher rpm power will be lifted.

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

A Motorsport camshaft is not great driving around busy urban areas.

You should ideally optimize your power band to your usage of the car so for a daily driver stick with a mild fast road N45B16 N45B20S camshaft

Some N45B16 N45B20S engines respond better to more aggressive camshaft durations than others.

The map and fuelling also have an effect on the bhp gains you'll hit.

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.

N45B16 N45B20S Tuning Stages

Stage 1 N45B16 N45B20S modifications: Panel air filters, Remaps/piggy back ECU, Fast road camshaft, Sports exhaust manifold, Intake headers, Drilled & smoothed airbox.

Stage 2 N45B16 N45B20S modifications: Fast road cam, fuel pump upgrades, Sports catalyst & performance exhaust, Ported and polished head, high flow fuel injectors, induction kit.

Stage 3 N45B16 N45B20S modifications: Twin charging conversions, Crank and Piston upgrades to alter compression, Adding or Upgrading forced induction (turbo/supercharger), Engine balancing & blueprinting, Competition cam, Internal engine upgrades (head flowing porting/bigger valves).

The N45B16 N45B20S engine blocks respond well to upgrades and thankfully there are increasing numbers of modifications and tuning parts out there.

Mapping should help to fully realize the full potential of all the mods you've done to your N45B16 N45B20S.

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but the end result will depend much on the mods you've fitted and the condition of your engine.

It is the whole point to any performance tuning project to force more air into the N45B16 N45B20S engine

Air Intake manifolds carry the air from the air filter and allow it to be drawn into the engine cylinders with fuel for the squish phase.

Shape and rate of flow of the Air Intake manifolds can make a substantial improvement to fuel delivery on the N45B16 N45B20S.

It's not uncommon that intake headers are in dire need of an upgrade, although some car makers provide well optimised intake headers.

Fitting big valve kits, getting N45B16 N45B20S port enlargement and head flowing will also increase performance, and as an added benefit will make space for an improved performance increase on other tuning parts.

Turbo upgrades for the N45B16 N45B20S

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 N45B16 N45B20S

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

When an engine is fitted with a turbo modifications are giving better power gains and you'll see that turbo engines use better components.

However most engines have limits

Research these limitations and upgrade to stronger pistons, crank and engine components to survive the power.

There are many car owners spending a loads on turbocharger upgrades on the N45B16 N45B20S only to see the N45B16 N45B20S explode when it's been finished.

Larger capacity turbo chargers commonly experience a bottom end lag, and low capacity turbo chargers spool up more quickly but do not have the peak end torque gains.

Over the last 20 years the market of turbos is always moving on and we commonly find variable vane turbos, permitting the vane profile is altered according to speed to lower lag and increase top end power.

Twin scroll turbos divert the exhaust gases into a couple of channels and direct these at differently angled vanes in the turbo. They also improve the scavenging effect of the engine.

You'll commonly see there's a restriction in the air flow sensor AFM/MAP on the N45B16 N45B20S when a lot more air is being drawn into the engine.

Going up you'll find 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 and torque gains, although more challenging to configure. We have this feature on twinchargers if you want to read more.

Uprating N45B16 N45B20S fuel injectors

When you lift the bhp you will need to increase to the fuel delivery.

More bhp needs more fuel. We would recommend you to over specify your injector capacity.

As a rule of thumb add 20% when fitting an injector, this allows for injector deterioration and affords a bit of spare capacity should the engine need 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.

Best N45B16 N45B20S performance exhausts

You should look to improve your exhaust if your exhaust is actually creating a restriction.

On most factory exhausts you should find that the exhaust flow rate is still 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 increase the flow of gases through the engine.

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

Common exhaust restrictions can be traced to the catalyst installed, so adding a faster flowing sports alternative will help avoid this restriction.

Problems and issues to look out for on the N45B16 N45B20S

The N45B16 N45B20S engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the N45B16 N45B20S, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your N45B16 N45B20S engine please join us in our friendly forum where you can discuss tuning options in more detail with our N45B16 N45B20S owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

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We really like hearing from our readers, and hearing about which tuning parts were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our N45B16 N45B20S guides and tips are kept up to date.

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