Tuning the BMW S50

"Comprehensive guide to tuning the BMW S50 engine!"

The BMW S50 offer good returns when tuned and with the best uprated tuning mods like ECU maps, turbo improvements and camshafts you will really maximize your driving enjoyment.

TorqueCars will provide a guide to S50 tuning and report on the premier upgrades.

The ultimate S50 tuning mods on an engine are sensibly the ones that give the biggest return for your cash.

We won't be swayed by popular S50 tuning mods, they need to be cost effective.

Significant gains on the S50 can be made from camshaft upgrades. Altering the camshaft profile alters the intake and exhaust durations on the engine and can dramatically change the power band and power output.

NB: Fast road camshafts commonly push up the torque over the rev range, you could sacrifice a little low down bhp but the top end will improve.

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

A Motorsport and race cam will just annoy you whilst on the daily commute.

You should ideally match your engines power to your preferences so for a road car stick with a mild fast road S50 cam

Some S50 engines respond better to mild cam durations so set your engine up on a rolling road.

The map and fuelling also will make differences on the power gains you'll make.

A longer valve duration can alter the power 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: Fast road camshaft, Drilled & smoothed airbox, Sports exhaust manifold, Panel air filters, Remaps/piggy back ECU, Intake headers.

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

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

The S50 engines are fantastic to work on and we're happy to report there are increasing numbers of mods and tuning parts around.

ECU flashing should help to unlock the full potential of all the upgrades you've fitted to your S50.

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 usually vary depending on the upgrades you've applied and the condition of your engine.

Pushing air into each cylinder is the whole point to any tuning task.

Intake carry the air from the air filter and allow it to be fed into the engine cylinders with fuel for the squish phase.

The bore size, shape and rate of flow of the Intake can make a substantial difference to to fuel engine efficiency on the S50.

I usually find intake headers are in dire need of performance upgrades, although some OEM provide decently flowing intake headers.

Fitting big valve kits, carrying out port matching and head flowing will also lift performance, this will allow you to get raising the 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 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.

When your motor has a turbo already fitted upgrades are simpler to install and you'll see that turbo engines already contain stronger components.

There are reliable limits for every engine, with some being over specified and some just sufficiently able to handle stock power

See where you'll find these limits and fit better quality components to cope with the power.

We've seen tuners spending a loads of money on turbocharger upgrades on the S50 only to experience the engine block go up in smoke on it's first outing after it's used on the roads.

Big turbos tend to experience a bottom end lag, and little turbos spool up more quickly but won't have the top end torque gains.

In recent times the choice of turbo chargers is always evolving and we are seeing variable vane turbo chargers, where the vane profile is altered according to speed to lower lag and increase top end torque.

Twin scroll turbo chargers divert the exhaust gases into two channels and feed these at differently designed vanes in the turbo charger. They also boost the scavenging effect of the engine.

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 sapped performance at a much lower level.

Adding a supercharger or additional turbo will make large torque gains, although more complex to setup. We have this in depth look at twinchargers if you want to read more.

Fuelling upgrades and mods

Don't miss you'll need to uprate the fuel system when you are increasing the bhp - it makes the car more thirsty. Most tuners we speak with say to be generous with your flow rate on the injectors.

The rule of thumb is to add another 20% when specifying an injector, helps cope with injector deterioration and allows a bit of 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 uprate your exhaust if your current exhaust is actually causing a restriction in flow.

On most factory exhausts you'll find the 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.

Sports exhausts generally help improve air flow from the engine but avoid an exhaust that is too large or you may end up will reduce the flow rate. Stick to 1.5 to 2.5 inches for best results.

Typically exhaust restrictions can be located the filters installed, so adding a better flowing race alternative will help avoid this restriction.

Weak spots, Issues & common problem areas on the S50

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

Regular oil changes are vital on the s50, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

Check for Vanos issues, rumbles and rough idle, the Vanos components should be replaced every 150000 miles .

For more information on Tuning your engine please join us in our friendly forum where you can discuss tuning options in more detail with our owners. It would also be worth reading our unbiased s50 tuning articles to get a full grasp of the benefits and drawbacks of each modification.

History of the Engine

  • S50B30
    (Eu) 213 kW (286 hp) @7,000 rpm 319Nm(235 lbft) @3,500 rpm
  • S50B30US (USA) 179 kW (240 hp) @6,000 rpm 305Nm(225 lbft) @4,250 rpm
  • S50B32 239 kW (321 hp) @7,400 rpm 350Nm(258 lbft) @3,250¬†rpm

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