Tuning the BMW M50

"Comprehensive guide to performance tuning the BMW M50 engine!"

Now we will detail the best approach to M50 tuning and report on the best mods that work. BMW M50 are fantastic to work on and with carefully chosen sports tuning mods like remapping, turbo upgrades and camshafts you will dramatically increase your driving pleasure.

Just because particular modifications are are common on M50 it doesn't mean it is good, so we'll ultimate modifications that will give your M50 the best value for money to power increase.

Significant gains on the M50 can be made from cam upgrades. Altering the cam profile alters the intake and exhaust durations on the engine and can dramatically change the power band and power output.

NB: Fast road cams normally push up the bhp and torque over the rev range, you could sacrifice a little low end bhp but the higher rpm power will be better.

Motorsport cams, push up the higher 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 match your bhp range to your driving style.

I'd be shocked if you have ever thought a M50 Motorsport camshaft is a pleasure to live with when on the daily commute.

Each engine responds better to different camshaft durations so set your engine up on a rolling road.

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

Longer valve 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.

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

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

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

The M50 engine blocks respond well to upgrades and we note that there are increasing numbers of mods and tuning parts around.

Remaps will help to establish the full potential of all the modifications you've fitted to your M50.

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but the outcome will vary depending on the modifications you've applied and the condition of your engine.

It is the main goal to any car tuning project to pull more air and fuel into the M50 engine

Intake headers flow the air during the suck phase from the filter and allow it to be drawn into the engine and mixed with fuel.

Design and flow characteristics of the Intake can make a big difference to to fuel atomisation on the M50.

Commonly we find the air intake manifolds are crying out for aftermarket tuning parts, although some makers provide decently flowing air intake manifolds.

Increasing the M50 valve size, doing some port matching and head flowing will also improve performance, and significantly will make space for an improved performance increase on other parts.

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 M50

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 a car has a turbo already fitted parts are going to make more power and we find turbo engines are made with harder and stronger components.

However engines will have power limits

Research these limits and install better quality components to utilize the power.

We see many tuners spending a loads of money on turbo upgrades on the M50 only to see the motor literally blow up when it's been finished.

Bigger upgraded turbochargers will usually experience a bottom end lag, and smaller turbochargers spool up more quickly but do not have the peak end bhp gains.

In the last 10 years the world of turbochargers is always improving and we are seeing variable vane turbochargers, where the vane profile is altered according to speed to lower lag and increase top end bhp.

Twin scroll turbochargers divert the exhaust gases into 2 channels and feed these at differently profiled vanes in the turbocharger. They also increase the scavenging effect of the engine.

It is common that there is a restriction in the air flow sensor MAF/MAP on the M50 when considerably more air is being drawn into the engine.

We note 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 gains, although more challenging to setup. We have this article covering twinchargers if you want to read more.

Fuelling upgrades and mods

You will need to ensure that the engine is not starved of fuel so need to pay attention to the fuelling when you start extending past 20% of a torque increase.Don't forget to be generous with your injector capacity.

The rule of thumb is to add 20% to the flow rate when buying an injector, helps cope with injector deterioration and affords a little spare capacity should the engine need 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 improve your exhaust if the existing exhaust is actually creating a restriction in flow.

On most factory exhausts you'll see the flow rate is still good 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 do not go too large or you could will reduce the flow rate. Stick to 1.5 to 2.5 inches for best results.

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

Weak spots, Issues & common problem areas on the M50

The M50 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

The Vanos components should be checked, carefully maintained and replaced at high milages.

Regular oil changes are vital on the M50, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your M50 engine please join us in our friendly forum where you can discuss tuning options in more detail with our tuning articles to get a full grasp of the benefits and drawbacks of each modification.

History of the Engine

  • M50B20 110 kW 148 hp @6,000 rpm 140 lbft @4,700 rpm
  • M50B20TU 110 kW 148 hp @5,900 rpm  140 lbft @4,200 rpm
  • M50B24TU 138 kW 185 hp @5,900 rpm 177 lbft @4,200 rpm
  • M50B25 141 kW 189 hp @6,000 rpm 181 lbft @4,700 rpm
  • M50B25TU 141 kW 189 hp @5,900 rpm  184 lbft @4,200 rpm
  • S50B30 Eu 213 kW 286 hp @7,000 rpm 319  lbft @3,500 rpm
  • S50B30US US179 kW 240 hp @6,000 rpm 305  lbft @4,250 rpm
  • S50B32 239 kW 321 hp @7,400 rpm 258 lbft @3,250 rpm

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We really like hearing from our readers, and hearing about which tuning parts were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our M50 guides and tips are kept up to date.

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