Tuning the BMW N40B16

"Comprehensive guide to performance parts and tuning the BMW N40B16 engine!"

We often are getting posts inquiring about getting more power from the N40B16 and wanting to know what are the things we are recommending when it comes to N40B16 mods that work. So let us look into BMW N40B16 tuning mods and outline the best mods that work on this great engine and point out some frequent tuning mistakes along the way.

The BMW N40B16 are popular engines and with the optimum tuning parts like a remap, turbo upgrades and camshafts you will positively improve your driving experience.

Here we look into N40B16 tuning and point out the best modifications.

When talking about the greatest parts for your N40B16 engine, we are going to focus on the ones that give the best power gain for you spend.

Altering your N40B16 cam will make a dramatic difference to the engine torque. Choosing a higher performance cam profile raises the torque accordingly.

NB: Fast road cams normally push up the power over the rev band, you could drop a little low down power but your high end rpm power will be lifted.

Race cams, push up the high end rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

In a road car should ideally to match your torque band to your typical driving style.

You'll never have ever thought a N40B16 Race camshaft is a pleasure to live with when on the daily commute.

Different N40B16 engines respond better to extreme camshaft durations than others.

The map and injectors and fuel pump also will make differences 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.

N40B16 Tuning Stages

Stage 1 N40B16 modifications: Fast road camshaft, Intake headers, Remaps/piggy back ECU, Drilled & smoothed airbox, Sports exhaust manifold, Panel air filters.

Stage 2 N40B16 modifications: Fast road cam, Ported and polished head, Sports catalyst & performance exhaust, induction kit, high flow fuel injectors, fuel pump upgrades.

Stage 3 N40B16 modifications: Adding or Upgrading forced induction (turbo/supercharger), Competition cam, Engine balancing & blueprinting, Twin charging conversions, Internal engine upgrades (head flowing porting/bigger valves), Crank and Piston upgrades to alter compression.

Plan your options and then buy your parts and set yourself a power target to avoid costly mistakes.

Mapping allows a tuner to fully realize the full potential of all the parts you've done to your N40B16.

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

Pulling fuel and air into the N40B16 engine is the whole point to any car tuning project.

Intake headers carry the air during the suck phase from the filter and allow it to be sucked into the engine cylinders.

The size of bore and shape and flow characteristics of the Intake manifold can make a big effect on to fuel atomisation and engine efficiency on the N40B16.

Many mass produced engine intake headers are needing an upgrade, although some car makers provide decently flowing intake headers.

Adding a N40B16 larger valve kit, doing a bit of port work and head flowing will also raise bhp, & more importantly will permit a better bhp increase on other mods.

Turbo upgrades for the N40B16

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 N40B16

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

When your motor is fitted with a turbocharger upgrades are giving better power gains and you'll see that turbo engines will have uprated components.

There are tuning limits for every engine, with some being extremely strong and some only just able to handle stock power

We recommend you find these limits and fit forged components to handle the power.

We've seen people spending a loads of money on turbo charger upgrades on the N40B16 only to watch the N40B16 catastrophically fail on it's first outing after it's been finished.

Big upgraded turbos often suffer low end lag, and low capacity turbos spool up more quickly but don't have the peak rpm power band gains.

Thankfully the selection of turbo units is always developing and we now see variable vane turbo units, allowing the vane angle is altered according to speed to lower lag and increase top end performance.

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

It is common that there's a restriction in the air flow sensor AFM/MAP on the N40B16 when loads 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 was restricting torque at a much lower level.

Adding a supercharger or additional turbo will make large performance gains, although more complex to setup. We have this article on twincharging if you want to read more.

Uprating N40B16 fuel injectors

Don't omit to look at the fuel system when you are increasing the performance - it makes the car more thirsty. It makes sense to be generous with your flow rate on the injectors.

As a rule of thumb add 20% to the flow rate when fitting an injector, this allows for injector deterioration and affords some 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 N40B16 performance exhausts

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

On most factory exhausts you'll see the exhaust flow rate is good 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 big or you may end up will reduce the flow rate. Stick to 1.5 to 2.5 inches as a rule of thumb.

Typically exhaust restrictions can be traced to the filters installed, so adding a faster flowing performance alternative will help avoid this restriction.

Problems and issues to look out for on the N40B16

The N40B16 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the N40B16, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your N40B16 engine please join us in our friendly forum where you can discuss tuning options in more detail with our N40B16 owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

We need your help to complete and improve this page, so do give us your feedback in the comments box below.

We really like hearing from our readers, and hearing about which upgrades were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our N40B16 guides and tips are kept up to date.

Check out my YouTube channel, we're regularly adding new content...


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