Tuning the BMW S52

"Comprehensive guide to tuning the BMW S52 engine!"

We shall detail the best approach to S52 tuning and provide tips on the best modifications for your car. BMW S52 are good project engines and with carefully picked uprated enhancements like remapping, turbo improvements and camshafts you will substantially enhance your driving enjoyment.

Just because particular mods are popular with S52 owners it doesn't mean its worth having, so we'll ultimate mods that will give your S52 the best power gain for you spend.

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

NB: Fast road cams commonly increase the bhp across the rev range, you could drop a little low end bhp but your top end will be better.

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

A Race cam makes it harder when driving in heavy traffic.

You should ideally match your power band to your cars usage so for a car used daily stick with a shorter duration S52 cam

Some S52 engines respond better to different cam durations check your engine on a rolling road.

The ECU mapping and fuelling also will say much on the torque gains you'll get.

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

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

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

Carefully think through your options and then source your tuning mods and set yourself a power target to avoid wasting your time and money.

ECU flashing should help to release the full potential of all the parts you've fitted to your S52.

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

It is the aim to any car tuning job to force fuel and air into your S52

The intake plenum take the air during the suck phase from the air filter and allow it to be sucked into the engine and mixed with fuel.

The size of bore and shape and flow rate of the Air Intake manifolds can make a noticeable difference to to fuel atomisation on the S52.

It's not uncommon that headers are needing motorsport parts, although a few car makers provide fairly well optimized headers.

Larger S52 valves, doing some port matching and head flowing will also increase bhp and torque, & more importantly will allow you to get raising the bhp and torque 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 S52

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 the engine is turbo charged upgrades are going to make more power and most turbocharged engines already contain stronger components.

However engines will have power limits

See where you'll find these restrictions and fit higher quality components to handle the power.

It's not unheard of guys spending a fortune on turbo upgrades on the S52 only to suffer the indignity of watching the car catastrophically fail on it's first outing after it's been enthusiastically driven.

Bigger upgraded turbochargers tend to experience no power at low rpm, and little turbochargers spool up quickly but don't have the high rpm engines power gains.

In the last 10 years the choice of turbochargers is always moving on and we commonly find variable vane turbochargers, where the vane angle is altered according to speed to lower lag and increase top end bhp and torque.

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

It is not unusual that there's a restriction in the air flow sensor AFM/MAP on the S52 when loads more air is being sucked into the engine.

We see 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor sapped power at a much lower level.

Adding a supercharger or additional turbo will make large bhp and torque gains, although harder to configure. We have this in depth look at 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 will need to look at the fuelling when you start going beyond 20% of a bhp increase.Most tuners we speak with say to over specify your injector capacity.

The rule of thumb is to add 20% capacity when buying an injector, which takes into account injector deterioration and gives 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

Only look to replace your exhaust if your exhaust is actually creating a flow problem.

On most factory exhausts you should find that the exhaust flow rate is still 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 will certainly help air flow out of the engine but do not go 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 are in the filters installed, so adding a freer flowing performance alternative will help avoid this restriction.

Weak spots, Issues & common problem areas on the S52

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

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

At high mileages it is recommended to change the Double Vanos and Lambda sensor.

Thermostat housing can start to leak coolant.

High oil consumption may be due to worn piston rings where oil seeps into the cylinders.

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 tuning articles to get a full grasp of the benefits and drawbacks of each modification.

History of the Engine

The S52 is a highly tuned variant of the M52 and ran from 1996-2000

The cast iron block of the M50 was, in most areas, replaced with an aluminium block with iron sleeves, this allowed the engine displacement to increase from 2.5 to 2.8 Liters.

The engine has a larger bore and stroke giving a 10.5:1 compression ratio. It also had camshafts mods with more lift and duration.

  • 240 hp (179 kW) at 6,000 rpm and 236 lbft (320 Nm) of torque at 3,800 rpm

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