BMW M50 Tuning

"All you need to know about tuning the BMW M50 engine!"

The BMW M50 are popular engines and with the ultimate sports enhancements like remapping, turbo upgrades and camshafts you will noticeably increase your driving fun.

Our aim here is to review M50 tuning and provide tips on the best upgrades.

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History, Power & Specs 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

Tuning the BMW M50 and best M50 performance parts.

Best M50 parts

The top M50 tuning mods on an engine are in our opinion the ones that give the best value for money.

We won't be swayed by popular M50 tuning mods, they need to be cost effective.

Altering your M50 camshaft will make a dramatic difference to the engine power band. Choosing a higher performance camshaft profile raises the power band accordingly.

Fast road cams tend to increase the torque over the rpm band, you may sacrifice a little low end bhp but your higher rpm power will be higher.

Competition cams, increase the higher rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

In a typical daily driver you need to optimize your power band to your preferences.

I'd be surprised if you find a M50 Race cam is a pleasure to live with when in heavy traffic because low end power will be very lumpy. Competition cams are designed for maximum power at the top end of the RPM range, a place that most daily commutes will not permit!

Some M50 engines respond better to different camshaft durations so view each engine as unique.

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

A longer valve duration 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.

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Best mods for your M50

  1. Mapping - A Remapped M50 ECU provides the most advantage for the money, replacement ECUs, and Tuning boxes are all alternatives.
  2. Air Induction and Exhaust - Note that on their own these mods will NOT ADD POWER in most cases, but they can help release power after other mods by lessening the restriction.
  3. Fast road cams are are often the best upgrade for an engine, but they must be setup by someone who knows what they are doing and tracking one down can be a challenge but you might have a local firm to regrind a stock cam for you.
  4. Flywheel lightening - a reduced weight flywheel will improve the engines rev changes. But not always suitable for all M50 engines.
  5. Flowing and porting the Head - Head work will get air flowing into the engine while removing turbulence or restrictions.
  6. Turbo Upgrades - Adding a turbocharger is the most significant way to improve intake air supply, this means you are able to use more fuel and make higher power. Although one of the most technically difficult mods it offers big gains.

M50 Tuning Stages

Typical stage 1 mods often include: Intake manifolds, Fast road camshaft, Remaps/piggy back ECU, Panel air filters, drilled & smoothed airbox, Sports exhaust header/manifold.

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

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

The M50 engine blocks make great tuning projects and we're finding that there are quite a few choices of parts and performance parts about.

remap helps fully realize the full potential of all the upgrades you've fitted to your M50.

(In some cases, as the factory ECU is locked flashing is not an option, so an aftermarket ECU is the route to take, and many of these will outperform factory ECU's but make sure it has knock protection and that you get it setup properly.)

It will usually give you around 30% more power on turbocharged vehicles and you can expect to see around 15% on NA (naturally aspirated) engines, but the end result usually depend much on the upgrades you've done and the condition of your engine.

It is the main goal to any tuning task to feed more air into each cylinder

Air Intake manifolds carry the air from the air filter and allow it to be sucked into the engine cylinders.

The shape and flow characteristics of the Intake can make a noticeable change to fuel mixing and power on the M50.

Many mass produced engine air intake manifolds are needing aftermarket parts, although a few manufacturers provide fairly well optimized air intake manifolds.

Adding a M50 larger valve kit, doing a bit of M50 port enlargement and head flowing will also boost performance, & importantly will give you an improved performance increase on other tuning parts.

M50 Turbo upgrades

NA (naturally aspirated) 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 major power gains.

When your motor has a turbocharger tuning parts are giving better power gains and you'll see that turbo charged engines are built with uprated components.

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

See where you'll find these limits and upgrade to forged components to survive the power.

It's not unheard of tuners spending a fortune on turbocharger upgrades on the M50 only to have the M50 explode when it's completed.

Large turbo chargers will usually experience a bottom end lag, and smaller turbo chargers spool up more quickly but do not have the peak rpm torque gains.

Thanks to new tech the choice of turbochargers is always moving on and we are seeing variable vane turbochargers, allowing the vane angle is altered according to speed to lower lag and increase top end torque.

Twin scroll turbochargers divert the exhaust gases into two channels and direct these at differently profiled vanes in the turbo. They also improve the scavenging effect of the engine.

It is common that there is a limitation in the air flow sensor MAF/MAP on these engines when a lot 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 was restricting performance at a much lower level.

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

M50 Fuelling

Don't overlook the need to raise the fuel delivery when you are increasing the bhp - it makes the car more thirsty. Most tuners we speak with say to over specify your injectors flow rate.

As a rule of thumb add 20% when buying an injector, this accounts for 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.

M50 Performance Exhausts

You only need to boost your exhaust if your current exhaust is actually causing a restriction.

On most factory exhausts you'll see the exhaust flow rate is 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 increase the flow of gases through the engine.

But if your exhaust pipe is too big, ie: it's over 2.5 inches bore, you will lose much of your flow rate and end up lacking power and torque.

Common exhaust restrictions are traced to the emissions filters installed, so adding a faster flowing race alternative such as a sports catalyst pretty much removes this restriction, thanks to it's larger size and surface area, and will effectively raise the performance to levels you would expect without having a catalyst installed, but keeps the car road legal.

Weak spots Issues & problem areas on the M50

The M50 engines are generally reliable and solid units, as long as you follow the manufacturers service schedules, and use a good quality oil to ensure longevity. Few problems should happen as long as they are regularly serviced and maintained.

Carbon build up in the head, particularly around the valves which will sap power or create flat spots, this is a larger issue on direct injection engines but should be looked out for on all engines. We have tips on removing carbon build up.

Some of our members have had issues with flat spots or glitches after applying mods and upgrades or tuning, this is not usually related to this engines design, so instead see our article on diagnosing flat spots and problems after tuning which should help you get the bottom of this issue.

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

Regular oil changes are vital on the M50, especially when tuned and will help extend the life and reliability of the engine.

If you would like to know more, or just get some friendly advice 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.

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We love to hear what our visitors have got up to and which tuning parts work best for you on your car. Which helps us keep our guides and tips up to date helping others with their modified car projects. Your feedback and comments are used to keep this page up to date, and help improve the accuracy of these M50 tuning guides which get regular updates and revisions.

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