Mercedes OM608 Tuning

"All you need to know about tuning the Mercedes OM608 engine!"

The Mercedes OM608 are good project engines and with carefully chosen sports upgrades like remapping, turbo upgrades and camshafts you will definitely improve your driving fun.

Our aim here is to outline options for your OM608 tuning and report on the premier modifications for your car.

History, Power & Specs of the OM608 Engine

Renault–Nissan–Mitsubishi Alliance Based on Renaults K9K

@OM608 DE15 SCR

85 kW (116 PS; 114 hp) @ 4,000 rpm 260 Nm (192 lbft) @ 1,750–2,500 rpm

2018–present W177 A180d

OM608 DE15 SCR

85 kW (116 PS; 114 hp) @ 4,000 rpm 260 Nm (192 lbft) @ 1,750–2,500 rpm

OM608 DE15 SCR

2018–present W177 A180d

Tuning the Mercedes OM608 and best OM608 performance parts.

Best OM608 tuning mods

Just because particular upgrades are are common on OM608 it doesn't mean it is good, we will recommend only what we regard as the greatest upgrades that will give your OM608 the best power gain for you spend.

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 bhp gains are on offer for camshaft upgrades.

Fast road camshafts normally boost the power through the rev band, you may sacrifice a little bottom end bhp but top end will improve.

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

A Motorsport camshaft won't do well if driving in heavy traffic.

You should ideally match your bhp range to your driving style so for a typical daily driver stick with a mild fast road OM608 camshaft

Some OM608 engines respond better to different cam durations so view each engine as unique.

The map and fuel pump and injectors also will say much on the bhp gains you'll make.

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

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

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

    Plan your options and then buy your mods and set yourself a power target to avoid disappointment.

    ECU mapping will help unlock the full potential of all the parts you've done to your OM608.

    (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 power output often differs on the parts you've applied and the condition of your engine.

    Pushing air into your OM608 is vital to any performance tuning job.

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

    Design and flow rate of the Intake can make a large change to fuel engine efficiency on the OM608.

    We often see air intake manifolds are in desperate need of performance upgrades, although some car makers provide well optimised air intake manifolds.

    Larger OM608 valves, doing some port work and head flowing will also increase bhp and torque, the fantastic side effect is it will allow you to get raising the bhp and torque increase on other tuning mods.

    OM608 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 OM608

    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 the engine is turbo charged tuning parts are more reliable and you'll see that turbocharged engines already contain many forged and stronger components.

    However you'll find engines will need better parts at higher power limits.It is important to find these limitations and upgrade to better quality components to survive the power.

    We've seen car owners spending a lot of money on turbo upgrades on the OM608 only to watch the engine explode just after it's been enthusiastically driven.

    Larger upgraded turbochargers often experience a bottom end lag, and smaller turbochargers spool up more quickly but don't have the high rpm engines power gains.

    Thanks to progress the selection of turbos is always developing and we now see variable vane turbos, where the vane angle is altered according to speed to lower lag and increase top end bhp.

    Twin scroll turbos divert the exhaust flow into a couple of channels and direct these at differently angled vanes in the turbo. They also improve the scavenging effect of the engine.

    It is not unusual that there is a restriction in the air flow sensor AFM/MAF on the OM608 when considerably more air is being drawn into the engine.

    You'll see that 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 gains, although more challenging to install. 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 will have to pay attention to the fuelling when you start exceeding 20% of a power increase.Don't forget to over specify your injector capacity.

    The rule of thumb is to add 20% capacity when fitting an injector, this takes into account injector deterioration and allows a little 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.

    OM608 Performance Exhausts

    You should look to uprate your exhaust if your current exhaust is creating a flow problem.

    On most factory exhausts you'll see the exhaust flow rate is 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 can help equal out the flow of air through the engine.

    But if the exhaust is too large, ie: over 2.5 inches bore, you will lose a lot of the exhaust flow rate and end up losing power and torque.

    Common exhaust restrictions come around the catalysts installed, so adding a freer 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 OM608

    The OM608 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 OM608, 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 OM608 engine please join us in our car forums where you can discuss OM608 tuning options in more detail with our OM608 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 OM608 tuning guides which get regular updates and revisions.

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