Mercedes OM654 Tuning

"All you need to know about tuning the Mercedes OM654 engine!"

Herein we examine OM654 tuning and provide tips on the premier modifications. Mercedes OM654 are popular tuning projects and with the right tuning modifications like ECU maps, turbo upgrades and camshafts you will dramatically maximise your driving fun.

History, Power & Specs of the OM654 Engine

OM 654

  • 143 kW (194 PS; 192 hp) at 3,800 rpm with peak torque of 400 Nm (295 lbft) at 1,600-2,400 rpm
  • 180 kW (245 PS; 241 hp) at 4,200 rpm 500 Nm (369 lbft) at 1,600-2,400 rpm

OM 654q

This was for transverse mounting.

Tuning the Mercedes OM654 and best OM654 performance parts.

Best OM654 upgrades

The best OM654 upgrades on an engine are usually the ones that give the biggest return for your cash.

We won't be swayed by popular OM654 upgrades, they need to be cost effective.

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

Fast road cams usually boost the bhp and torque throughout the rpm range, you might lose a little low end torque but the top end will be lifted.

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

For a road car must carefully try to match your bhp range to your cars usage.

I would be surprised if you have found a OM654 Motorsport and race cam is a pleasure to live with when in heavy traffic because low end power will be very lumpy. Competition cams are designed for maximum power at the top end of the RPM range, a place that most daily commutes will not permit!

Different OM654 engines respond better to less aggressive camshaft durations so view each engine as unique.

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

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

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

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

    Plan your options and then buy your upgrades and set yourself a power target to save yourself from expensive mistakes.

    ECU flashing will help to establish the full potential of all the parts you've done to your OM654.

    (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 the outcome may vary depending on the parts you've applied and the condition of your engine.

    It is the main goal to any engine modification job to shove more fuel and air into your OM654

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

    The size of bore and shape and rate of flow of the Intake manifolds can make a large difference to fuel mixing and power on the OM654.

    On popular production engines intake manifold are needing aftermarket tuning parts, although a few manufacturers provide well optimised intake manifold.

    Increasing the OM654 valve size, doing a bit of port matching and head flowing will also raise performance, & importantly will give you increasing the performance increase on other tuning mods.

    OM654 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 OM654

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

    When a car is fitted with a turbocharger parts are simpler to install and you'll see that turbo charged engines are made with many forged and stronger components.

    There are practical limits for every engine, with some being very over engineered and some only just able to handle stock powerWe recommend you find these restrictions and upgrade to better quality components to utilize the power.

    We've seen guys spending a lots of money on turbo charger upgrades on the OM654 only to watch the whole thing catastrophically fail on it's first outing after it's completed.

    Big upgraded turbo units tend to experience a bottom end lag, and low capacity turbo units spool up more quickly but won't have the peak end power band gains.

    Over the last 20 years the market of turbochargers is always evolving and we now see variable vane turbochargers, allowing the vane angle is altered according to speed to lower lag and increase top end bhp and torque.

    Twin scroll turbochargers divert the exhaust gases into a couple of channels and feed these at differently profiled vanes in the turbocharger. They also improve the scavenging effect of the engine.

    It is not unusual that there's a limitation in the air flow sensor AFM/MAP on the OM654 when a lot more air is being drawn 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 bhp gains, although harder to get working. We have this in depth look at twinchargers if you want to read more.


    Don't miss you'll need to raise the fuel delivery when you are increasing the bhp - it makes the car more thirsty. We strongly recommend you to over specify your flow rate on the injectors.

    As a rule of thumb add 20% when fitting an injector, this takes into account injector deterioration and gives 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.

    OM654 Performance Exhausts

    You only need to uprate your exhaust if the existing exhaust is actually causing a restriction.

    On most factory exhausts you should find that your flow rate is still good 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 can usually air flow out of the engine but avoid an exhaust that is too big or you might just stuff your flow rate and make things worse. So generally speaking, keep to a size of 1.5 to around 2.5 inches to maximise flow rates, and this should take into account the amount of air your engine is moving.

    Common exhaust restrictions are in the filters installed, so adding a better flowing performance catalyst removes the restriction. We note that performance cats perform similarly to decats and have the added benefit of keeping your car street legal, as decats or catalyst removal is illegal in most territories for road going cars.

    Weak spots, Issues & problem areas on the OM654

    The OM654 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 OM654, 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 OM654 engine please join us in our car forums where you can discuss OM654 tuning options in more detail with our OM654 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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