BMW S52 Tuning

"All you need to know about tuning the BMW S52 engine!"

Revving into the heart of performance enthusiasts, the BMW S52 engine emerges as a remarkable feat of engineering. This inline-6 powerhouse, often revered for its role in the iconic BMW M3 (E36), boasts a symphony of advanced features that set it apart.

At its core, the S52 engine showcases a robust design, with a displacement of 3.2 liters, ensuring a thrilling drive. Notably, it's equipped with a sophisticated variable valve timing system, known as VANOS, which enhances the engine's efficiency and power across various RPMs.

It was based on the M52 engine but has certainly evolved, with focus on strength, better cooling and more performance oriented head (cams & valvetrain).

This engine offers a commendable power output range, making it not just a joy to drive, but also a canvas for tuning enthusiasts. Its compatibility with various aftermarket parts, including turbochargers and performance exhaust systems, makes it an ideal choice for those looking to maximize their driving experience.

Why does the S52 engine stand out as an exemplary project car base? The answer lies in its blend of raw power, reliability, and the vast availability of aftermarket support. This engine's robust design ensures longevity, even under the stress of high-performance modifications.

Whether it's upgrading the turbocharger for more power or fine-tuning the exhaust for a deeper growl, the S52 provides a solid and reliable foundation. Its widespread popularity among car enthusiasts means a wealth of knowledge and resources are readily available, making it easier to embark on your customization journey.

The straight-6 DOHC petrol engine S52 is one of BMW's finest ever creations. E36 M3 from 1996–1999.. able to respond to adjustments. It has a huge following in the aftermarket. If you like, the S52 is also a good candidate for forced induction. An iron block and solid bottom end can handle a lot of boost.

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History, Power & Specs 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

Tuning the BMW S52 and best S52 performance parts.

Best S52 upgrades

When looking to enhance the performance of a BMW S52 engine, many consider upgrading the camshaft, despite the existing VANOS system already doing a commendable job in altering the cam profile.

VANOS, BMW's variable valve timing system, adjusts the camshaft position, optimizing engine performance and efficiency. However, for those seeking to further fine-tune their engine's performance, camshaft upgrades offer additional benefits.

A popular choice is a camshaft kit with 276/270 durations, a notable step up from the stock 264/256 durations found in US models. This upgrade increases the valve lift and durations, effectively altering the engine's breathing characteristics for improved power delivery.

You'll generally see power approaching 280hp with a set of suitable cams.

An essential component of this upgrade is the Race Camshaft VANOS Shim. This shim limits the travel of the VANOS mechanism, allowing for the increased lapse in piston to valve contact.

This modification means that these performance camshafts can work seamlessly with the standard valve reliefs in OEM spec pistons, negating the need for extensive engine modifications.

The other option is to choose alternative pistons with a larger relief for the valves to sit in. Maximising flow into the S52 is the key here and this doesn't always mean a large valve curtain.

Choosing cams is a very specialised area. I consider myself fortunate to live where I do and have access to two CAM specialists less than an hours drive away from me.

Alongside the camshaft upgrade, it's crucial to invest in a performance spring kit. This kit ensures that the valvetrain can handle the increased lift and duration without valve float or other issues at high RPMs.

While camshaft upgrades can significantly enhance engine performance, especially in terms of higher RPM power, there are potential drawbacks. These include a rougher idle, increased engine noise, and potentially decreased low-end torque.

Moreover, these upgrades often require supporting modifications and fine-tuning to realize their full potential, potentially adding to the overall cost and complexity of the project. Nonetheless, for car enthusiasts and those seeking to maximize their BMW S52's performance, these upgrades offer a path to a more engaging and powerful driving experience.

The intake & exhaust durations will alter depending on the chosen cam profile, so large power band gains are on offer for cam upgrades.

Performance profile or "Fast road cams" tend to boost the bhp and torque across the top end of the rpm range, you might lose a little bottom end torque but your top end will be higher.

Different S52 engines respond better to extreme cam durations check your engine on a rolling road.

The engine timing and fuelling also will make differences on the torque gains you'll get.

A longer valve duration 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.

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Best mods for your S52

  1. Flowing and porting the Head - Head work will get air flowing into the engine while removing turbulence or restrictions.
  2. Remaps - A tune/remap ensures the biggest gains in terms of cost, replacement ECUs, and piggyback ECUs are all alternatives.
  3. Fast road Camshafts are are often the best (and most complex) upgrade for an engine, but they must be fitted by someone who knows what they are doing and you might struggle to find one but there might be a local firm to regrind a stock camshaft .
  4. Turbo upgrades - forced induction improvements are the most efficient approach to improve intake air supply, allowing you to use more fuel and make higher power. It is one of the most challenging mods it offers big gains.
  5. Air Induction and Exhaust - Note that on their own these mods won't ADD POWER in most cases, but they can help enhance power after other mods by removing the restriction.
  6. Lighter flywheels - a lighter flywheel will improve the engines rev changes. But not always suitable for all S52 engines.
  7. High Compression Pistons - on a NA engine like the S52 many seek to improve the ability to compress fuel and air with a revised crank and pistons.

S52 Tuning Stages

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

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

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

Carefully think through your options and then acquire your tuning parts and set yourself a power target to save yourself from expensive mistakes.

DME Tunes/Remapping

The DME is the computer responsible for managing and controlling various aspects of the engine's operation, including fuel injection, ignition timing, and emissions control.

It plays a critical role in ensuring optimal engine performance, efficiency, and compliance with emission standards.ECU mapping should help to release the full potential of all the tuning parts you've fitted to your S52.

(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 15% more power through most of the RPM range on a typical stock S52, but the end result may rely on the tuning parts you've fitted and the condition of your engine.

Upgrading or remapping the Engine Control Unit (ECU) of a BMW S52 engine is a common and effective way to enhance its performance, especially after making hardware modifications like intake, exhaust, or turbo upgrades. You have two primary options: remapping the existing ECU or installing an aftermarket ECU.

Remapping the Stock ECU:

  • Remapping, or "chipping," involves modifying the software within the stock ECU to change fueling, ignition timing, and other parameters.
  • This can be done by specialists who can tailor the map to your specific engine setup and performance goals.
  • It's a cost-effective way to improve performance, especially for mild to moderate modifications.

Aftermarket ECUs:

  • For more extensive modifications, or if you need more control over engine parameters than a remap can provide, an aftermarket ECU is the way to go.
  • Aftermarket units offer greater flexibility and control, allowing for fine-tuning of every aspect of engine performance.
  • Popular brands for aftermarket ECUs that work well with the S52 engine include Haltech, AEM, and MoTeC. These brands are known for their advanced features, reliability, and support.
  • Keep in mind that switching to an aftermarket ECU often requires a more comprehensive approach, including potentially rewiring the engine harness and definitely a custom tune from a professional.

In both cases, the goal is to optimize the engine's performance characteristics to suit your needs, whether it's for daily driving, track use, or high-performance applications.

It's crucial to have a professional tuner perform these upgrades, as improper tuning can lead to engine damage.

The tuner can also ensure that the modifications work harmoniously with other upgrades you've made to the engine.

Ultimately, the choice between remapping and an aftermarket ECU depends on the extent of your modifications, your performance goals, and your budget.

It is vital to any engine tuning task to shove more fuel and air into each cylinder

Air Intake manifolds transmit the air from the filter and allow it to be drawn into the engine and mixed with fuel.

The size of bore and shape and flow characteristics of the Intake manifolds can make a noticeable effect on to fuel mixing and power on the S52.

We often see air intake manifolds are ripe for motorsport parts, although a few car makers provide well optimised air intake manifolds.

Fitting big valve kits, carrying out S52 port enlargement and head flowing will also increase torque, and more importantly will afford you raising the torque increase on other parts.

S52 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 S52 but we would caution against it, you'd be practically rebuilding the entire block.

Upgrading the turbo on a BMW S52 engine can significantly enhance its power and performance. The S52, originally a naturally aspirated engine, gains a considerable boost in horsepower and torque when equipped with a turbocharger.

This upgrade transforms the driving experience, offering exhilarating acceleration and improved overall performance.

When selecting a turbo upgrade for the S52, it's important to consider reputable brands known for their quality and compatibility with BMW engines. A kit will provide all the bits you'll need and you'll have the confidence of knowing the R&D development has been done for you.

Some of the well-regarded brands in the turbocharging world include Garrett, Pure, BorgWarner, RB, and Precision Turbo. These brands offer a range of options, from more modest setups for street use to high-performance turbos for racing applications.

The typical power outputs or gains from a turbo upgrade can vary greatly depending on the turbocharger selected, the engine's condition, and supporting modifications.

For a moderately upgraded S52 engine, it's common to see power gains ranging from 100 to 300 horsepower over the stock output, depending on the boost level and the turbo's size.

More aggressive setups, particularly when paired with other performance enhancements like upgraded fuel systems, stronger internals, and advanced tuning, can push the power gains even higher.

It's crucial to remember that turbocharging a naturally aspirated engine like the S52 isn't just about bolting on a turbo. It requires a holistic approach to engine modification.

This includes upgrading the fuel and ignition systems, reinforcing engine internals, and ensuring adequate cooling to handle the increased power and heat. Additionally, a professional tune is essential to ensure the engine runs safely and efficiently with the new turbo setup.

Overall, turbo upgrading the BMW S52 engine offers substantial performance benefits, making it a popular choice for enthusiasts looking to extract maximum power from their vehicle. With the right setup and supporting modifications, an S52 with a turbo upgrade can become a formidable force on the road or track.

It is common that there's a limit in the air flow sensor AFM/MAF on the when considerably 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 limited bhp at a much lower level.

Adding a supercharger or additional turbo will make large performance gains, although more difficult to install. We have this guide to twinchargers if you want to read more.

S52 Fuelling Upgrades

When you boost the torque you will need to pay attention to the fuel delivery.

More torque needs more fuel and Most tuners we speak with say to over specify your injectors flow rate by around 20%.

Upgrading the fuel system on a BMW S52 engine is crucial, especially when making other performance enhancements like turbocharging or supercharging.

The stock fuel system may not be capable of supplying the increased fuel demand of a more powerful engine. Key components of a fuel system upgrade typically include fuel pumps and fuel injectors.

Fuel Pumps: The fuel pump is responsible for delivering fuel from the tank to the engine. For a performance-enhanced S52, the stock pump might not provide sufficient flow.

Upgrading to a high-flow fuel pump ensures that the engine receives the necessary fuel volume, especially under high load and high RPM conditions. Brands like Walbro, Bosch, and Deatsch Werks are popular choices among BMW enthusiasts for their reliability and performance.

Fuel Injectors: Upgrading fuel injectors is another critical aspect. Performance injectors can deliver more fuel at a higher pressure, which is essential for maintaining the correct air-fuel ratio in a modified engine.

This becomes especially important in turbocharged or supercharged applications where more air is entering the engine, necessitating more fuel for optimal combustion. Brands like Injector Dynamics, Bosch, and Siemens offer high-performance injectors that are compatible with the S52 engine.

When selecting injectors, it's important to choose the right size, measured in pounds per hour (lb/hr) or cubic centimeters per minute (cc/min), depending on the expected power output.

Oversized injectors can lead to poor idling and fuel control, while undersized injectors can starve the engine at high loads.

Considerations: With any fuel system upgrade, it's essential to ensure compatibility with the rest of the engine and the specific performance goals.

This might involve consulting with a tuning professional or a BMW specialist to determine the appropriate specifications for your setup. Additionally, when increasing fuel flow, it's also important to consider upgrades to the fuel pressure regulator and fuel lines for a comprehensive upgrade.

S52 Performance Exhaust Upgrades

You may need to replace your exhaust if the current exhaust is actually creating a restriction.

On most factory exhausts you'll see the flow rate is good even on modest power gains, but when you start pushing up the power levels you will need to get a better flowing exhaust.

Note that with the biggest exhaust you can buy you'll slow up the exhaust flow rate - the best for power gains are usually between 2.5 and 3 inches. It is the shape and material more than the bore size and the aim is to maximize VELOCITY, which large bore sizes only do at higher RPM ranges.

Usual exhaust restrictions can be traced to the filters installed, so adding a higher flowing high performance aftermarket one will improve air flow, and rather than doing an illegal decat, will keep the car road legal in most areas and regions.

S52 Lighter Flywheels

Installing a lighter flywheel in a BMW S52 engine can bring noticeable improvements in the engine's responsiveness and overall performance.

A lighter flywheel reduces the rotational mass connected to the engine. This means the engine can rev up and down more quickly. The result is a more responsive throttle, particularly noticeable during quick acceleration and deceleration.

Because there is less mass for the engine to spin, more of the engine's power can be used to move the car, rather than just moving the flywheel. This often leads to quicker acceleration times, as the engine can reach its optimal RPM range faster.

Many drivers appreciate the more 'connected' feel they get with a lighter flywheel. The engine's revs are more directly linked to the throttle input, providing a more engaging driving experience, especially in performance or track settings.

However, there are some trade-offs to consider:

  • Potential for Increased Engine Stall: Because a lighter flywheel stores less rotational energy, it can lead to an increased likelihood of stalling, particularly at low RPMs. This can be more noticeable in stop-start traffic or when moving off from a standstill.
  • Rougher Idle: The reduced mass can also lead to a rougher or more uneven idle, as the engine is less able to smooth out the natural pulses of the combustion process.
  • Reduced Low-End Torque: In daily driving conditions, especially in traffic or at low speeds, a lighter flywheel might make the car feel less smooth as it removes some of the inertia that helps keep the engine turning.

PMC motorsport are selling a single mass flywheel upgrade suitable for the M52. Bear in mind BMW have already reduced the flywheel weight from the S50 engine so I feel this mod is only suitable for extensively modified S52 engines where peak RPM power is the goal.

Internal Engine Mods For the S52

Upgrading to high compression pistons and a revised crankshaft in a BMW S52 engine can significantly enhance its performance. These modifications are typically pursued by enthusiasts looking to maximize power, especially in naturally aspirated setups.

Interestingly many opt for lower compression pistons when going with forced induction on the S52, so having a clear idea of your final aims is important when embarking on major internal engine mods.

High Compression Pistons:

  • High compression pistons increase the engine's compression ratio, which can lead to more power and a more responsive throttle.
  • Higher compression ratios allow the engine to extract more mechanical energy from the fuel-air mixture, resulting in better efficiency and power output.
  • However, it's important to note that increasing the compression ratio may require using higher octane fuel to prevent knocking or pre-detonation.
  • When upgrading pistons, it's also common to consider upgrading the connecting rods to handle the increased stress, especially if the engine will be used for high-performance or racing applications.

Revised Crankshaft:

  • A revised or upgraded crankshaft can be used to alter the engine's displacement or to improve its durability under high-performance conditions.
  • Stroked crankshafts increase the displacement of the engine, leading to more torque and power. This involves increasing the crankshaft’s stroke length, which effectively increases the volume of the cylinders.
  • Upgraded crankshafts are often constructed with higher-strength materials and designed to withstand higher stresses than the stock unit.


  • These modifications often require careful planning and execution. Increasing compression ratios or changing displacement affects many aspects of engine operation, including the air-fuel mixture, ignition timing, and valvetrain dynamics.
  • It's crucial to recalibrate or reprogram the DME (Digital Motor Electronics) or ECU (Engine Control Unit) to accommodate these changes. This ensures that the engine runs safely and efficiently with the new setup.
  • Upgrading to high compression pistons and a revised crankshaft is usually part of a comprehensive engine rebuild or overhaul, which might also include upgrading other internal components, such as the camshaft, valves, and cylinder heads.

In summary, while high compression pistons and a revised crankshaft can offer significant performance benefits, they require a holistic approach to engine tuning and modification.

S52 Weak Spots Issues & problem areas on the S52

The BMW S52 engine, revered for its performance and reliability in models like the E36 M3 and Z3 M, is generally robust, but like any engine, it does have some common issues that owners should be aware of:

VANOS System Failure:

The Variable Valve Timing system, known as VANOS, can fail or become noisy, especially in higher mileage engines. Symptoms include a loss of power, rough idling, and increased fuel consumption. Rebuilding or replacing the VANOS unit is often the recommended solution.

Keep a watch on the VANOS and replace it if it begins acting up after 10 years of ordinary driving. This is a regular issue with such a complicated system. So at high mileages it is recommended to change the Double Vanos and Lambda sensor.

Cooling System Weaknesses

The cooling system in BMWs with the S52 engine can be a weak point. Issues such as failing water pumps, brittle plastic radiator tanks, and thermostat failures are common. Regular maintenance and upgrading to more durable components can help mitigate these problems.

One area to look out for in particular is the thermostat housing which can start to leak coolant.

Oil Leaks

Common areas for oil leaks include the valve cover gasket, oil filter housing gasket, and the oil pan gasket. Regular inspections and timely gasket replacements can prevent more significant issues.

High oil consumption may be due to worn piston rings where oil seeps into the cylinders. You'll notice oil levels dropping and blue exhaust smoke as this problem develops.

Worn Timing Chain Guides

The timing chain guides can wear out over time, leading to potential timing chain failure. This is more common in engines that have been neglected or have very high mileage.

Rod Bearing Wear

While less common than in the later S54 engine, the S52 can still suffer from rod bearing wear, especially under high-performance or track conditions. Regular oil changes with high-quality oil and occasional inspections can help.

Mass Air Flow Sensor (MAF) Issues

The MAF sensor can become dirty or fail, leading to performance issues like hesitation and poor fuel economy. Cleaning or replacing the MAF sensor can resolve these issues.

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 Lambda sensor's readings are skewed when there are air leaks in the intake manifold. The S52 engine is prone to this and it is quite well documented but can cause lumpy running, poor idling and misfires.

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

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