Mercedes M178 Tuning

"All you need to know about tuning the Mercedes M178 engine!"

Herein we review and look at M178 tuning and point out the best upgrades. Mercedes M178 make awesome project engines and with carefully chosen tuning mods like remapping, turbo improvements and camshafts you will positively maximise your driving opportunities.

History, Power & Specs of the M178 Engine

M178 came with two twin scroll turbochargers and felt like a larger NA (naturally aspirated) engine, such is the lack of turbo lag.

510 PS 503 hp at 6,250 rpm 650 Nm 479 lbft at 1750 – 4750 rpm

  • GT C 190 2015-2017 340 kW 462 PS 456 hp 6000 600 Nm 443lbft 1,600-5,000
  • GT C 190 2017 350 kW 476 PS 469 hp 6000 630 Nm 465lbft 1,700-5,000
  • GT S C 190 2015-2017 375 kW 510 PS 503 hp 6250 650 Nm 479lbft 1,750-4,750
  • GT S C 190 2017 384 kW 522 PS 515 hp 6250 670 Nm 494lbft 1,800-5,000
  • GT C C 190 2017 410 kW 557 PS 550 hp 5,750-6,750 680 Nm 502lbft 1,900-5,500
  • GT R C 190 2017 430 kW 585 PS 577 hp 6250 700 Nm 516lbft 1,900-5,500
  • Brabus B40S 2017 478 kW 650 PS 641 hp 6500 820 Nm 605lbft 1,750-4,500
  • GT Black Series 2021 537 kW 730 PS 720 hp 6,700-6,900 800 Nm 590lbft 2,000-6,000

Tuning the Mercedes M178 and best M178 performance parts.

Best M178 mods

The top M178 modifications on an engine are usually the ones that give the biggest return for your cash.

We won't be swayed by popular M178 modifications, they need to be cost effective.

Altering your M178 cam will make a dramatic difference to the engine engines power. Choosing a higher performance cam profile raises the engines power accordingly.

Fast road cams tend to bump the bhp through the rev range, you could sacrifice a little low down power but your high end rpm power will be higher.

Competition cams, bump the high end rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

A Race cam won't do well if driving around busy urban areas. This is because a competition cam causes a very lumpy idle, and makes the car more prone to stall or jerk along in stop start traffic, sadly though many ignore this and end up ruining a perfectly good car and having to revert back to a fast road, or OEM cam profile.

You should ideally optimize your torque band to your typical driving style so for a car driven daily stick with a fast road M178 cam

Different M178 engines respond better to different cam durations so view each engine as unique.

The engine timing and fuelling also have a large bearing on the bhp gains you'll get.

Extending exhaust or intake durations 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.

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

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

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

    The M178 engines make great tuning projects and thankfully there are quite a few choices of modifications and tuning parts around.

    ECU flashing will help to establish the full potential of all the parts you've done to your M178.

    (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 figures achieved may depend much on the parts you've done and the condition of your engine.

    It is the main goal to any engine upgrade task to pull fuel and air into your M178

    Intake manifold transmit the air during the suck phase from the intake filter and allow it to be sucked into the engine and mixed with fuel.

    Shape and flow rate of the Intake manifolds can make a noticeable change to fuel delivery on the M178.

    Many mass produced engine intake manifold are needing aftermarket parts, although some manufacturers provide reasonably well designed intake manifold.

    Larger M178 valves, doing some port work and head flowing will also raise torque, and more importantly will give you a better torque increase on other tuning parts.

    M178 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 M178

    The more air you can get into an engine, the more fuel it can burn and uprating the induction with a turbocharger upgrade makes significant power gains.

    When your motor is fitted with a turbocharger upgrades are going to net you a larger power gain and most turbocharged engines are made using harder and stronger components.

    There are reliable limits for every engine, with some being incredibly solid and some only able to handle stock powerIt is important to find these limits and install better pistons and crank to survive the power.

    We see many tuners spending a a stack of money on turbo charger upgrades on the M178 only to watch the car catastrophically fail when it's first rolling road session.

    Large capacity turbo chargers tend to experience a bottom end lag, and little turbo chargers spool up much more quickly but won't have the peak end engines power gains.

    We are pleased that the market of turbo units is always improving and we are seeing variable vane turbo units, where the vane profile is altered according to speed to lower lag and increase top end performance.

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

    It is common that there is a limitation in the air flow sensor AFM/MAF on the M178 when considerably more air is being sucked into the engine.

    You'll see that 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor was restricting torque at a much lower level.

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


    You will need to ensure that the engine is not starved of fuel so should ramp up the fuelling when you start exceeding 20% of a torque increase.It is important to be generous with your injector capacity.

    The rule of thumb is to add 20% capacity when specifying an injector, this takes into account injector deterioration and provides a bit of spare capacity should the engine require 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.M178 Performance Exhausts

    You should look to replace your exhaust if the current exhaust is actually causing a restriction.

    On most factory exhausts you should find that the exhaust 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 increase the flow of air through the engine.

    But if the exhaust is too large, ie: it's over 2.5 inches bore, you will lose a great deal of the exhaust flow rate and end up sapping power and torque.

    Typically exhaust restrictions are traced to the catalysts 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.

    Weak spots, Issues & problem areas on the M178

    The M178 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 M178, 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 M178 engine please join us in our car forums where you can discuss M178 tuning options in more detail with our M178 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.

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    We love hearing about our website visitors projects, especially the mods done and which 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 M178 tuning guides which get regular updates and revisions.

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