Tuning the BMW M43

"Comprehensive guide to tuning the BMW M43 engine!"

Our aim here is to look at M43 tuning and highlight the greatest mods that work. BMW M43 are awesome to work on and with the ultimate motorsport parts like a remap, turbo kits and camshafts you will really increase your driving opportunities.

The ultimate M43 modifications on an engine are obviously the ones that give the best value for money.

We won't be swayed by popular M43 modifications, they need to be cost effective.

Significant gains on the M43 can be made from cam upgrades. Altering the cam profile alters the intake and exhaust durations on the engine and can dramatically change the torque and power output.

NB: Fast road camshafts usually bump the performance throughout the rpm range, you may sacrifice a little bottom end power but high end rpm power will be better.

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 Motorsport cam is not great driving in heavy traffic.

You should ideally optimize your torque band to your usage of the car so for a daily driver stick with a shorter duration M43 cam

Different M43 engines respond better to different cam durations than others.

The ecu map and fuelling also have an effect on the bhp gains you'll achieve.

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

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

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

Review your options and then buy your upgrades and set yourself a power target to save yourself from expensive mistakes.

Remaps allows a tuner to to establish the full potential of all the modifications 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 the end result usually differs on the modifications you've fitted and the condition of your engine.

Feeding fuel and air into your M43 is the whole point to any car tuning task.

Intake headers flow the air from the filter and allow it to be drawn into the engine cylinders.

The shape and flow characteristics of the Intake headers can make a big improvement to fuel delivery on the M43.

Many mass produced engine headers are begging for aftermarket tuning parts, although a few makers provide fairly well optimized headers.

Fitting big valve kits, doing a bit of 3 or 5 angle valve jobs and porting and head flowing will also raise bhp and torque, & more importantly will raise potential for a better bhp and 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 significant power gains.

If your car has forced induction parts are going to net you a larger power gain and you will discover turbo engines are built using harder and stronger components.

However you will find an engines will have power limits

We recommend you find these limitations and install stronger pistons, crank and engine components to survive the power.

There are many car owners spending a lots of money on turbo upgrades on the M43 only to have the car go up in smoke on it's first outing after it's been finished.

Large upgraded turbo chargers will usually experience no power at low rpm, and smaller turbo chargers spool up quickly but won't have the high rpm power band gains.

In recent times the selection of turbochargers is always evolving and we commonly find variable vane turbochargers, where the vane angle is altered according to speed to lower lag and increase top end performance.

Twin scroll turbochargers divert the exhaust gases into 2 channels and direct these at differently angled vanes in the turbo charger. They also increase the scavenging effect of the engine.

You'll commonly see there's a limit in the air flow sensor (AFM/MAF/MAP) on the M43 when loads more air is being pulled into the engine.

You'll see that 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor sapped bhp at a much lower level.

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

Fuelling upgrades and mods

Don't omit to ramp up the fuel system when you are increasing the performance - it makes the car more thirsty. We would recommend you to over specify your injectors flow rate.

As a rule of thumb add 20% capacity when fitting an injector, this allows for injector deterioration and allows 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.

Exhaust upgrades and mods

You should look to increase your exhaust if your exhaust is creating a flow problem.

On most factory exhausts you'll see the exhaust flow rate is still fine even on modest power gains, but when you start pushing up the power levels you will need to get a better flowing exhaust.

Please dont run with the largest exhaust you can get you'll reduce the exhaust flow rate - the best for power gains are usually between 1.5 to 2.5 inches. It is the shape and material more than the bore size.

Typically exhaust restrictions can be located the catalysts installed, so adding a higher flowing performance alternative will help avoid this restriction.

Weak spots, Issues & common problem areas on the M43

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

Regular oil changes are vital on the M43, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

History of the Engine

The M43 is a SOHC straight 4 block.

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

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.

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

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