Modding and performance tuning parts for the BMW S50 engine!

Tuners tips on "S50 Modifications"

S50 Modifications Guide

How to modify and upgrade the BMW S50

"Comprehensive guide to performance parts and tuning the BMW S50 engine!"

Our friends at TorqueCars are always getting messages about how to improve the S50 from people wanting to know what are the ultimate S50 modifications. So let us look into BMW S50 parts and outline the best upgrades on this great engine and point out some frequent tuning mistakes along the way.

Therefore we examine S50 tuning and point out the best modifications for your car. BMW S50 are popular engines and with the optimum modified parts like a remap, turbo kits and camshafts you will substantially improve your driving opportunities.

Just because particular tuning mods are popular with S50 owners it doesn't mean it is good, we shall focus on the optimum tuning mods that will give your S50 the best value for money to power increase.

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'.

S50 induction kits

Improving air intake on the S50

You need air matched to fuel for an engine to work. If there is too little fuel then it will run lean, if there is too little air it runs rich losing power . We'll pick up on fuelling later in this article but for now we shall look at air supply.

So Getting air into your S50 is the whole point to any car tuning project.

You'll commonly see there is a limit in the air flow sensor MAF/MAP on the S50 when loads more air is being pulled 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.

Headers transmit the on the suck phase from the filter and allow it to be pulled into the engine cylinders with fuel for the squish phase.

The shape and rate of flow of the Air Intake manifolds can make a big effect on to fuel mixing and power on the S50.

We often see plenum chambers are in desperate need of performance upgrades, although a few makers provide decently flowing plenum chambers.

Larger S50 valves, getting port work and head flowing will also boost torque, & more importantly will allow you to get increasing the torque increase on other tuning parts.

S50 performance cam tips.

Some S50 engines respond better to less aggressive camshaft durations so view each engine as unique.

The ECU mapping and injectors and fuel pump also have a large bearing on the bhp gains you'll hit.

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.

The camshaft profile plays a big part in the engines power output so camshaft upgrades make quite a large difference. The intake & exhaust durations will alter depending on the chosen camshaft profile, so large bhp gains are on offer for camshaft upgrades.

NB: Fast road camshafts usually increase the bhp and torque over the rev range, you could sacrifice a little bottom end torque but the top end will improve.

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

A Race camshaft makes it harder when driving around busy urban areas.

You should ideally optimize your power band to your usage of the car so for a car driven daily stick with a mild fast road S50 camshaft

Stage 1, 2 and 3 mods for the S50

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 S50 parts:

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

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

Stage 2 S50 parts:

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

Stage 3 S50 parts:

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

The S50 power trains respond well to upgrades and thankfully there is a lot of upgrades and tuning parts about.

ECU mapping should help to fully realize the full potential of all the mods you've done to your S50.

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 rely on the mods you've done and the condition of your engine.

Turbo modifications on the S50

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 S50.

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.

If your car has forced induction parts are simpler to install and most turbocharged engines will have better components.

However you'll find engines will need better parts at higher power limits

Discover these limits and install forged components to survive the power.

There are many people spending a fortune on turbo charger upgrades on the S50 only to suffer the humiliation of seeing the whole thing throw a rod on it's first outing after it's been enthusiastically driven.

Large upgraded turbo units often suffer no power at low rpm, and smaller turbo units spool up more quickly but do not have the high rpm bhp gains.

In recent times the choice of turbos is always improving and we now see variable vane turbos, where the vane profile is altered according to speed to lower lag and increase top end performance.

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

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large torque gains, although more challenging to configure. We have this in depth look at twinchargers if you want to read more.

Tips about fuel supply on the S50

Don't miss you'll need to raise the fuelling when you are increasing the bhp - it makes the car more thirsty. Don't forget to over specify your injectors flow rate.

The rule of thumb is to add another 20% when fitting an injector, this takes into account injector deterioration and gives some spare capacity should the engine require 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 S50 performance exhaust upgrades

The only time you should look to increase your exhaust system with an upgraded one is if the existing exhaust is actually causing a restriction.

On most factory exhausts you'll find the flow rate is ok 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.

Do not go with the biggest exhaust you can find this will slow the exhaust rate - the best exhausts for power gains are usually between one and a half to two and half inches. Your exhaust design, the bend angles and construction are what have more effect on flow rates than your pipe width to a certain extent. So the exhaust design is a big factor.

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

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

Faults issues and things to look out for on the S50

Like most engines an S50, 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 S50, failure to do this will exacerbate engine wear, on a tuned S50 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 S50 why not pop over to the forums at TorqueCars where you can chat about S50 tuning options and read about others projects who may be planning to do similar modifications on their S50.

We need your help to complete and improve this page, so do give us your feedback in the comments box below.

We want to know your experiences with upgrades on your S50, it helps us improve our tips and keeps us current so please use the comments box to drop a tip.

If you liked this page please share it with your friends, drop a link to it in your favourite forum or use the bookmarking options to save it to your social media profile.

Check out TorqueCars new YouTube channel, and see their awesome new content...


Please use our forums if you wish to ask a tuning question, and please note we do not sell parts or services, we are just an online magazine.

Help us improve, leave a suggestion or tip

Your Constructive comments on this article