BMW M43 Tuning

"All you need to know about performance parts and tuning the BMW M43 engine!"

Our aim here is to review M43 tuning and outline the best modifications. BMW M43 provide a fun base for your project and with the best mods like ECU maps, turbo upgrades and camshafts you will substantially increase your driving enjoyment.

History of the Engine

The M43 is a SOHC straight 4 block.

  • M43B16 1,596 cc
  • 75 kW (102 PS) at 5500 rpm 150 N⋅m (111 lb⋅ft) at 3900 rpm 1991
    60 kW (82 PS) at 5500 rpm 127 N⋅m (94 lb⋅ft) at 3900 rpm 1995-2000
  • M43B18 1,796 cc
  • 85 kW (115 PS) at 5500 rpm 168 N⋅m (124 lb⋅ft) at 3900 rpm 1993
    74 kW (100 PS) at 5500 rpm 142 N⋅m (105 lb⋅ft) at 3900 rpm 1995-1996
  • M43B19 1,895 cc
  • 87 kW (118 PS) at 5500 rpm 180 N⋅m (133 lb⋅ft) at 3900 rpm 1998
    77 kW (105 PS)  at 5300 rpm 165 N⋅m (122 lb⋅ft)  at 2500 rpm 1999

Tuning the BMW M43 and best M43 performance parts.

Best M43 tuning parts

When talking about the best greatest for your M43 engine, we are going to concentrate on the tuning mods that give the biggest return for your cash.

Altering your M43 camshaft will make a dramatic difference to the engine engines power. Choosing a higher performance camshaft profile raises the engines power accordingly.

Fast road camshafts normally bump the power across the rpm band, you may sacrifice a little low down power but your high end rpm power will be higher.

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

A Race cam won't do well if in heavy traffic.

You should ideally optimize your bhp range to your usage of the car so for a car used daily stick with a mild fast road M43 cam

Some M43 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 will say much on the bhp gains you'll achieve.

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.

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

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

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

The M43 units make great tuning projects and thankfully there is a lot of modifications and tuning parts out there.

ECU mapping allows a tuner to to establish the full potential of all the tuning parts you've fitted to your M43.

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

Forcing more fuel and air into your M43 is the aim to any tuning project.

Intake manifold flow the air from the filter and allow it to be sucked into the engine cylinders with fuel for the squish phase.

The shape and flow characteristics of the Intake can make a noticeable effect on to fuel atomisation and engine efficiency on the M43.

Many mass produced engine intake manifold are ripe for aftermarket tuning parts, although a few OEM provide fairly well optimized intake manifold.

Fitting big valve kits, doing some port work and head flowing will also increase torque, and as an added benefit will give you a better torque increase on other modifications.

Turbo upgrades

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 M43

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

When your motor is turbo charged mods are relatively easy and we find turbo charged engines use stronger components.

However you will find an engines will have power limits

It is important to find these limitations and upgrade to forged components to survive the power.

There are many guys spending a lots of money on turbo charger upgrades on the M43 only to have the M43 literally blow up just after it's first rolling road session.

Larger capacity turbos often experience a bottom end lag, and little turbos spool up really quickly but don't have the peak rpm bhp gains.

In recent times the range of turbo chargers is always increasing and we now see variable vane turbo chargers, allowing the vane angle is altered according to speed to lower lag and increase top end performance.

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

It is common that there is a restriction in the air flow sensor AFM/MAP on the when loads more air is being drawn 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.

Adding a supercharger or additional turbo will make large torque gains, although more complex to configure. We have this article covering twinchargers if you want to read more.

Fuelling

When you raise the bhp you will need to pay attention to to the fuelling.

More bhp needs more fuel. Don't forget to be generous with your flow rate on the injectors.

The accepted safe increase is to add another 20% when specifying an injector, this accounts for injector deterioration and allows you some spare capacity should the engine require 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.

All the following flywheel power targets will assume an injector duty cycle of 80% and a base of 58psi of fuel pressure at idle.

4 Cylinder NASP engines

  • 58 PSI 285cc/min 200hp
  • 58 PSI 426cc/min 300hp

4 Cylinder supercharged engines

  • 58 PSI 312cc/min 200hp
  • 58 PSI 468cc/min 300hp

Exhaust

You may need to increase your exhaust if your exhaust is actually causing a restriction in flow.

On most factory exhausts you should find that your flow rate is still ok 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 usually air flow out of the engine but avoid an exhaust that is too big or you could will reduce the flow rate. Stick to 1.5 to 2.5 inches as a rule of thumb.

Common exhaust restrictions can be traced to the catalysts installed, so adding a better flowing performance alternative will help avoid this restriction.

Weak spots Issues & problem areas on the M43

The engines are generally reliable and solid as long as they are regularly serviced and maintained.

Regular oil changes are vital on the M43, especially when tuned and will help extend the life and reliability of the engine.

For more information on Tuning your M43 engine please join us in our friendly forum where you can discuss M43 tuning options in more detail with our owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

Please help us improve these tips by sending us your feedback in the comments box below.

We love to hear what our visitors have got up to and which mods work best for them on each model of car. Comments are used to improve the accuracy of these articles which are continually updated.

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