Mercedes M159 Tuning

"All you need to know about tuning the Mercedes M159 engine!"

The Mercedes M159 offer good returns when tuned and with a few sensible parts like ECU maps, turbo upgrades and camshafts you will positively improve your driving enjoyment.

We shall look into M159 tuning and provide tips on the ultimate modifications.

History, Power & Specs of the M159 Engine


  • 571 PS 420 kW 563 hp at 6,800 rpm 650 Nm 479lbft at 4,750 rpm
  • 591 PS 435 kW 583 hp at 6,800 rpm 650 Nm 479lbft at 4,750 rpm
  • 631 PS 464 kW 622 hp at 7,400 rpm 635 Nm 468lbft at 5,000 rpm

Tuning the Mercedes M159 and best M159 performance parts.

Best M159 upgrades

The best M159 mods on an engine are typically the ones that give the biggest return for your cash.

We won't be swayed by popular M159 mods, they need to be cost effective.

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

Fast road cams normally increase the power across the rev range, you might lose a little low down bhp but your higher rpm power will be lifted.

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

For a typical daily driver must carefully try to optimize your bhp range to your preferences.

I'd be amazed if you find a M159 Race camshaft is a pleasure to live with when driving in heavy traffic. The low end idle will be very lumpy and irregular, so something you would notice on a track when you drive in the upper third of the rpm band, but on roads this is a serious issue and we've heard from lots of drivers lamenting their decision to add an extreme competition cam profile to their engine.

Some M159 engines respond better to less aggressive cam durations than others.

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

Longer valve durations 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.

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Best Engine Mods for your car

  1. Engine Tunes - engine tuning/remapping provides the most advantage in terms of cost savings,  aftermarket ECUs, and piggyback ECUs are all alternatives.
  2. Fast road cams are one of the most significant mechanical changes, but they must be installed by someone who knows what they're doing and they are not always easy to source but you might find a local firm to regrind a stock camshaft.
  3. Intake and Exhaust - Note that on their own these mods will NOT ADD POWER in most cases, but they can help enhance power after other mods by removing the restriction.
  4. Upgrades to turbochargers and superchargers - forced induction is the most efficient approach to increase air supply, allowing you to burn more fuel and make more power. It is one of the most costly upgrades but provides the best gains.
  5. Head work - The goals of porting and flowing the head are to get air flowing into the engine while removing flow restrictions and turbulence.
  6. Typical stage 1 mods often include:
    Remaps/piggy back ECU, drilled & smoothed airbox, Sports exhaust header/manifold, Fast road camshaft, Intake manifolds, Panel air filters.

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

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

    Plan your options and then find your tuning mods and set yourself a power target to avoid wasting your time and money.

    A remap helps fully realize the full potential of all the parts you've done to your M159.

    (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 your results will differs on the parts you've done and the condition of your engine.

    Pushing air and fuel into your M159 is the whole point to any performance tuning project.

    Intake manifolds carry the air during the suck phase from the air filter and allow it to be pulled into the engine cylinders.

    Structure and rate of flow of the Plenum can make a noticeable improvement to fuel mixing and power on the M159.

    We often see intake manifold are in dire need of an upgrade, although some manufacturers provide decently flowing intake manifold.

    Fitting big valve kits, carrying out M159 port enlargement and head flowing will also increase performance, and significantly will permit a greater performance increase on other mods.

    M159 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 M159

    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.

    If a car is turbocharged, modifications are going to net you a larger power gain and turbo charged engines will have better components.

    However most engines have limits.We recommend you find these restrictions and upgrade to more solid crank and pistons to survive the power.

    We've seen mechanics spending a a stack of money on turbo charger upgrades on the M159 only to suffer the indignity of watching the car throw a rod on it's first outing after it's first rolling road session.

    Large capacity turbo chargers commonly suffer no power at low rpm, and little turbo chargers spool up much more quickly but don't have the top end power band gains.

    In recent times the range of turbo chargers is always evolving and we now see variable vane turbo chargers, permitting the vane angle is altered according to speed to lower lag and increase top end power.

    Twin scroll turbo chargers divert the exhaust flow into two channels and flow these at differently angled vanes in the turbo. They also help the scavenging effect of the engine.

    It is not unusual that there is a limit in the air flow sensor AFM/MAP on the M159 when a lot more air is being pulled into the engine.

    Going up you'll find 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 harder to configure. We have this feature on twinchargers if you want to read more.


    When you boost the bhp you will need to ramp up to the fuel system.

    More bhp needs more fuel. We strongly recommend you to over specify your flow rate on the injectors.

    The accepted safe increase is to add 20% when buying an injector, which takes into account injector deterioration and provides some 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.

    M159 Performance Exhausts

    Only look to increase your exhaust if the existing exhaust is actually creating a restriction.

    On most factory exhausts you should find that the exhaust 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 widest exhaust you can source you'll slow up the exhaust flow rate - the best for power gains are usually between 1.5 to 2.5 inches. It is the shape and material more than the bore size.

    Common exhaust restrictions can be traced to the catalyst and filters installed, so adding a better flowing high performance aftermarket one will improve air flow, and rather than doing an illegal decat, will keep the car road legal.

    Weak spots, Issues & problem areas on the M159

    The M159 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.

    Regular oil changes are vital on the M159, 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 M159 engine please join us in our car forums where you can discuss M159 tuning options in more detail with our M159 owners. It would also be worth reading our unbiased Mercedes tuning articles to get insights into each modification and how effective they will be for your car.

    Please help us improve these tips by sending us your feedback in the comments box below.

    We love to hear what our visitors have got up to and which upgrades 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 M159 tuning guides which get regular updates and revisions.

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