Modding uprating the BMW M40 engine!

All you need to know about "M40 Modifications"

M40 Modifications Guide

How to modify and upgrade the BMW M40

"Comprehensive guide to tuning the BMW M40 engine!"

Our friends at TorqueCars are regularly getting posts asking about how to improve the M40 from people wanting to know what are the things tuners recommend when it comes to M40 power upgrades. So let us look into BMW M40 parts and outline the best upgrades on this great engine and point out some frequent tuning mistakes along the way.

The BMW M40 great bases for a tuning project and with the right performance upgrades like remaps, turbo improvements and camshafts you will definitely maximize your driving experience.

This pages aim is consider M40 tuning and outline the premier modifications for your car.

Just because particular mods are are common on M40 it doesn't mean its worth having, we shall concentrate on the top mods that will give your M40 the biggest power gain return for your cash.

Without us subscribing to the mentality 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'.

M40 induction kits

Improving air intake on the M40

You need air and fuel for an engine to work. If there is too little fuel then it will run lean, if there is a lack of air it runs rich resulting in lost power which risks damage to the M40. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So Getting fuel and air into your M40 is the primary aim to any engine modification task.

It is common that there is a limitation in the air flow sensor MAP/MAF/AFM on the M40 when loads more air is being sucked 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.

Air Intake manifolds transmit the during the engines suck phase from the filter and allow it to be sucked into the engine cylinders.

Design and rate of flow of the air Intake manifold can make a substantial improvement to fuel engine efficiency on the M40.

On popular production engines intake are in desperate need of motorsport parts, although some OEM provide reasonably good intake.

Big valve conversions on the M40, doing a bit of 3 or 5 angle valve jobs and porting and head flowing will also increase power, and significantly will allow you to get a greater power increase on other upgrades.

M40 performance cam tips.

Different M40 engines respond better to more or less aggressive cam durations check your engine on a rolling road.

The map and fuel pump and injectors also have a large bearing on the torque gains you'll make.

Extending exhaust or intake durations 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 and exhaust durations will alter depending on the chosen camshaft profile, so large torque gains are on offer for camshaft upgrades.

NB: Fast road camshafts normally bump the performance across the rpm range, you might lose a little low down torque but the top end will be better.

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

A Motorsport and race camshaft won't do well if driving around busy urban areas.

You should ideally match your bhp range to your typical driving style so for a daily driver stick with a fast road M40 camshaft

Stage 1, 2 and 3 mods for the M40

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 M40 parts:

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

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

Stage 2 M40 parts:

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

Stage 3 M40 parts:

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

The M40 power plant respond well to mods and thankfully there is an increase of mods and performance parts about.

Remaps will help to establish the full potential of all the modifications you've done to your M40.

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 usually depend much on the modifications you've applied and the condition of your engine.

Turbo modifications on the M40

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 M40.

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

When an engine has a turbo already fitted mods are simpler to install and you'll see that turbo charged engines will have harder and stronger components.

There are reliable limits for every engine, with some being incredibly solid and some only able to handle stock power

We recommend you find these limits and install better quality components to utilize the power.

There are many people spending a lots of money on turbo charger upgrades on the M40 only to have the motor literally blow up soon after it's been enthusiastically driven.

Large turbos will usually suffer no power at low rpm, and low capacity turbos spool up more quickly but don't have the peak end engines power gains.

In the last 10 years the market of turbochargers is always moving on and we now see variable vane turbochargers, permitting the vane profile is altered according to speed to lower lag and increase top end bhp and torque.

Twin scroll turbochargers divert the exhaust flow into 2 channels and flow these at differently angled 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 more challenging to configure. We have this article on twincharging if you want to read more.

Tips about fuel supply on the M40

When you boost the torque you will need to uprate to the fuel delivery.

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

The accepted safe increase is to add 15% capacity when fitting an injector, helps cope with injector deterioration and gives a little 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 M40 performance exhaust upgrades

We'd only recommend you look to improve your exhaust system with an upgraded one is if the current exhaust is actually causing a restriction.

On most factory exhausts you should find that your flow rate is fine 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 out of the engine but do not go too large or you could will reduce the flow rate. Stick to one and a half to two and half inches as a rule of thumb.

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

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

Faults issues and things to look out for on the M40

Like most engines an M40, 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 M40, failure to do this will exacerbate engine wear, on a tuned M40 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 M40 why not pop over to the forums at TorqueCars where you can chat about M40 tuning options and read about others projects who may be planning to do similar modifications on their M40.

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