Modding uprating the BMW N40B16 engine!

The Lowdown on "N40B16 Modifications"

How to modify and upgrade the BMW N40B16

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

TorqueCars often are seeing threads requesting information on how to improve the N40B16 from people inquiring about getting more power from the N40B16 and wanting to know what are the things tuners recommend when it comes to N40B16 power upgrades. So let us look into BMW N40B16 tuning mods and outline the best upgrades on this great engine and point out some problems along the way.

This pages aim is provide a guide to N40B16 tuning and report on the premier upgrades. BMW N40B16 are good project engines and with carefully chosen motorsport parts like ECU maps, turbo kits and camshafts you will substantially maximize your driving pleasure.

The optimum N40B16 upgrades on an engine are as we have found the ones that give the biggest return for your money.

We won't be swayed by popular N40B16 upgrades, they need to be cost effective.

N40B16 induction kits

Improving air intake on the N40B16

You need air matched to fuel for an engine to work. If there is not enough fuel then it will run lean, if there is little flow of air it runs rich resulting in lost power . We'll pick up on fuelling later in this article but for now we shall look at air supply.

So the whole point to any tuning task to push air into your N40B16 but this has a knock on effect with the air flow sensor.

It is not unusual that there is a limit in the air flow sensor AFM/MAF on the N40B16 when loads more air is being sucked into the engine.

We see 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor was restricting performance at a much lower level.

Engines intake headers flow the on the suck phase from the air cleaner and allow it to be fed into the engine cylinders.

Structure and flow rate of the Headers can make a big effect on to fuel mixing and power on the N40B16.

We often see air intake manifolds are in dire need of aftermarket tuning parts, although some manufacturers provide reasonably good air intake manifolds.

Big valve conversions on the N40B16, getting 3 or 5 angle valve jobs and porting and head flowing will also raise torque, and significantly will afford you an improved torque increase on other upgrades.

N40B16 performance cam tips.

Different N40B16 engines respond better to extreme cam durations check your engine on a rolling road.

The map and fuelling also have an effect on the torque gains you'll make.

A longer valve duration can alter the torque 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.

The camshaft profile plays a big part in the engines power output so camshaft upgrades make quite a large difference. The intake & exhaust durations will alter depending on the chosen camshaft profile, so large power band gains are on offer for camshaft upgrades.

NB: Fast road camshafts usually raise the bhp and torque over the rev band, you could drop a little low end torque but the high end rpm power will be better.

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

On a car used daily you need to optimize your power band to your usage of the car.

I'd never find a N40B16 Motorsport camshaft is a pleasure to live with when in heavy traffic.

Stage 1, 2 and 3 mods for the N40B16

Before we break the best tuning upgrades down into stages of tune, let's list the most effective tuning upgrades for you.

  1. Suspension Upgrades - always improve your cars handling
  2. Brake Upgrades - Even before adding power improve those brakes
  3. Intake - make sure the intake is not restricted, use filters and intake upgrades to improve this
  4. Exhaust - as with 3 ensure there is not restriction in the exhaust, cats are the usual bottleneck
  5. Tunes - remapping, piggyback ECU's and aftermarket ECU's can all make decent gains
  6. Fuelling - when you've increased power you'll need to match this with more fuel
  7. Turbo upgrades - Improving the intake with a large turbo and better flowing intercooler will be the biggest power gain you'll see (but one of the most complex).

This video guide to tuning cars is a great starting point to work from in your project.

Stage 1 N40B16 parts:

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

Stage 2 N40B16 parts:

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

Tuning tips and articles Engine tuning Transmission tuning Care care Intake & exhaust mods Improve handling Forums

Stage 3 N40B16 parts:

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

The N40B16 power trains are fantastic to work on and thanks to their popularity there is an increase of mods and tuning parts about.

Remapping should help to release the full potential of all the upgrades you've done to your N40B16.

You will typically expect to see gains of approximately 20-30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but power output will depend much on the upgrades you've fitted and the condition of your engine.

Turbo modifications on the N40B16

To get a turbo working on a NASP engine there is a lot involved, from lowering compression ratio to improved fuel supply and mapping, so we have found a great guide to helpavoid the common pitfalls or end up with an unfinished project because you were not told what you were getting into by doing this on the 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 excellent power gains.

When your motor has forced induction modifications are going to net you a larger power gain and you'll see that turbocharged engines will have more solid components.

There are practical limits for every engine, with some being over specified and some just sufficiently able to handle stock power

See where you'll find these restrictions and fit higher quality crank and pistons to utilize the power.

There are many guys spending a lot of money on turbo upgrades on the N40B16 only to have the motor explode just after it's been enthusiastically driven.

Large upgraded turbochargers will usually experience low end lag, and smaller turbochargers spool up quickly but don't have the top end power band gains.

Thanks to new tech the choice of turbos is always developing and we are seeing variable vane turbos, allowing the vane profile is altered according to speed to lower lag and increase top end bhp and torque.

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

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large bhp and torque gains, although harder to install. We have this feature on twinchargers if you want to read more.

Tips about fuel supply on the N40B16

Don't overlook the need to ramp up the fuel delivery when you are increasing the performance - it makes the car more thirsty. Experienced mechanics will tell you to over specify your injectors flow rate.

As a rule of thumb add 15% to the flow rate when fitting an injector, this accounts for injector deterioration and gives a bit of spare capacity should the engine require more fuel.

Don't forget that different fuel grades will usually require different settings, a high octane fuel will burn more efficiently than lower octane fuel for example. A car will trim fuel supply to keep within the ideal air fuel mix but at the extreme ends you may need to adjust your injector capacity, or the mapping or you'll get flat spots and potential lean or rich fuel issues..

Recommended N40B16 performance exhaust upgrades

You only need to to boost your exhaust system with an upgraded one is if your exhaust is actually causing a flow problem.

On most factory exhausts you'll find the flow rate is still ok even on modest power gains, but on a serious tuning project with a big boost in power you will certainly need to get a better flowing exhaust.

Sports exhausts increase the flow of air through the engine.

But if your exhaust pipe is too big, ie: it's over two and a half inches diameter, you will lose a lot of the exhaust flow rate and end up sapping power and torque.

Usual exhaust restrictions can be traced to the catalyst installed, so adding a higher flowing race alternative will help avoid this restriction.

Decat pipes (NB:catalysts reduce harmful engine emissions) is illegal in most countries and regions.

Faults issues and things to look out for on the N40B16

Like most engines an N40B16, should have few issues if it gets properly serviced and looked after.

We cannot stress enough the need for oil changes with the correct grade of oil on the N40B16, failure to do this will exacerbate engine wear, on a tuned N40B16 this is more important than ever and close attention should be paid to your maintenance schedule.

If you are interested in learning more or getting impartial tuning advice for your N40B16 why not pop over to the forums at TorqueCars where you can chat about N40B16 tuning options and read about others projects who may be planning to do similar modifications on their N40B16.

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