Tuning guide "N40 Modifications"

N40 Modifications Guide

How to modify and upgrade the BMW N40

"Comprehensive guide to tuning the BMW N40 engine!"

TorqueCars are always getting emails asking about how to improve the N40 from people inquiring about getting more power from the N40 and wanting to know what are the premier N40 mods that work. So let us look into BMW N40 upgrades and outline the best modifications on this great engine and point out some frequent tuning mistakes along the way.

We shall look at N40 tuning and report on the ultimate modifications for your car. BMW N40 make awesome project engines and with the optimum motorsport upgrades like a remap, turbo kits and camshafts you will greatly maximize your driving pleasure.

Just because particular tuning parts are are common on N40 it doesn't mean its worth having, instead we'll focus on the best tuning parts that will give your N40 the best power gain for you money.

Without us subscribing to the popular myth of 'if it's shiny and makes more noise it must be good' you seem to get in many tuning magazines and on car forums'.

N40 induction kits

Improving air intake on the N40

You need air and 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 and potentially damaging the engine. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So the aim to any car tuning task to push air and fuel into each cylinder but this has a knock on effect with the air flow sensor.

You'll commonly see there's a limitation in the air flow sensor MAF/MAP on the N40 when loads more air is being pulled into the engine.

When tuning you may well find you need to get an air sensor or flow meter capable of upto 4 bars to cope with quite large power gains, whereas the OEM air sensor limited bhp at a much lower level.

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

The bore size, shape and flow characteristics of the air Intake manifold can make a substantial difference to to fuel delivery on the N40.

It's not uncommon that headers are ripe for aftermarket parts, although a few makers provide reasonably well designed headers.

Fitting big valve kits, carrying out 3 or 5 angle valve jobs and porting and head flowing will also boost torque, & more importantly will make space for raising the torque increase on other parts.

N40 performance cam tips.

Different N40 engines respond better to more or less aggressive camshaft durations check your engine on a rolling road.

The ecu map and injectors and fuel pump also will make differences on the power gains you'll hit.

Altering valve durations can alter the power 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.

Significant air intake, and exhaust improvements on the N40 can be made from cam upgrades. Changing the cam profile alters the intake and exhaust durations on the engine and can dramatically change the bhp and power output.

NB: Fast road cams normally bump the performance through the rpm band, you could sacrifice a little bottom end torque but high end rpm power will be lifted.

Motorsport and race cams, bump 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 car used daily you should ideally to match your engines power to your preferences.

I'd be shocked if you have ever thought a N40 Motorsport and race cam is a pleasure to live with when in heavy traffic.

Stage 1, 2 and 3 mods for the N40

Stage 1 N40 parts:

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

Stage 2 N40 parts:

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

Stage 3 N40 parts:

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

Plan your options and then source your upgrades and set yourself a power target to avoid costly mistakes.
Tuning tips and articles Engine tuning Transmission tuning Care care Intake & exhaust mods Improve handling Forums

Remapping will help unlock the full potential of all the tuning parts you've done to your N40.

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 the outcome will depend much on the tuning parts you've fitted and the condition of your engine.

Turbo modifications on the N40

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 N40.

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.

If your car is turbocharged, mods are more reliable and you will discover turbocharged engines are built using uprated components.

There are common areas of failure for every engine, with some being extremely strong and some only just able to handle stock power

It is important to find these restrictions and fit more solid crank and pistons to survive the power.

We see many guys spending a fortune on turbocharger upgrades on the N40 only to have the car catastrophically fail on it's first outing after it's been completed.

Larger turbos tend to experience no power at low rpm, and smaller turbos spool up much more quickly but won't have the peak end bhp gains.

Thanks to new tech the world of turbos is always developing 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 two channels and direct these at differently designed vanes in the turbo charger. They also improve the scavenging effect of the engine.

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large power gains, although more challenging to setup. We have this in depth look at twinchargers if you want to read more.

Tips about fuel supply on the N40

When you raise the power you will need to uprate to the fuel system.

More power needs more fuel. Most tuners we speak with say to be generous with your injector capacity.

The rule of thumb is to add another 15% when buying an injector, this takes into account injector deterioration and affords you some spare capacity should the engine need 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 N40 performance exhaust upgrades

We'd only recommend you look to increase your exhaust system with an upgraded one is if your current exhaust is actually causing a flow problem.

On most factory exhausts you'll find your 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 can usually air flow through the engine but do not go too big or you may end up will reduce the flow rate. Stick to one and a half to two and half inches for best results.

Usual exhaust restrictions come around the catalyst installed, so adding a freer flowing sports alternative will help avoid this restriction.

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

Faults issues and things to look out for on the N40

Like most engines an N40, 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 N40, failure to do this will exacerbate engine wear, on a tuned N40 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 N40 why not pop over to the forums at TorqueCars where you can chat about N40 tuning options and read about others projects who may be planning to do similar modifications on their N40.

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