Mercedes OM626 Tuning

"All you need to know about tuning the Mercedes OM626 engine!"

The Mercedes OM626 have loads of potential and with the right uprated mods like remaps, turbo upgrades and camshafts you will increase your driving pleasure.

The OM626 is another Renault–Nissan–Mitsubishi Alliance project based on Renaults R9M

Let us examine the options for your OM626 tuning and point out the optimum modifications for your car.

History, Power & Specs of the OM626 Engine

  • 130 PS (96kW 128hp) @4000rpm 320 Nm (236 lbft) @1750rpm
  • 136 PS (100kW 134hp) @4000rpm 330 Nm (243 lbft) @1750rpm
  • 160 PS (118kW 158hp) @4000rpm 380 Nm (280 lbft) @1750rpm
  • 180 PS (132kW 178hp) @4000rpm 400 Nm (295 lbft) @1750rpm

It was fitted to quite a few popular Renault, Nissan and Mercedes models.

R9M 130ps

  • 2014 - Mercedes Vito
  • 2014 - Mercedes C Class
  • 2015 - Renault Kadjar
  • 2016 - Renault Talisman

R9M 160PS (this is a twin turbo unit)

  • 2011- Renault Captur Concept Car
  • 2015- Renault Espace
  • 2015- Renault Talisman

Tuning the Mercedes OM626 and best OM626 performance parts.

Best OM626 tuning parts

Just because particular tuning parts are popular with OM626 owners it doesn't mean its worth having, we shall focus tuning parts that will give your OM626 the best power gain for you spend.

Altering your OM626 cam will make a dramatic difference to the engine torque. Choosing a higher performance cam profile raises the torque accordingly.

Fast road cams commonly boost the bhp across the rev range, you may lose a little bottom end bhp but high end rpm power will improve.

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

In a typical daily driver should ideally to optimize your bhp range to your driving style.

I'd be surprised if you find a OM626 Race cam 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.

Different OM626 engines respond better to different cam durations so set your engine up on a rolling road.

The engine timing and injectors and fuel pump also will say much on the bhp gains you'll achieve.

Longer valve 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.

Please watch our video which covers the 5 principles of tuning your car. Be sure to keep up with our latest YouTube content and subscribe.

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

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

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

    Carefully think through your options and then buy your tuning mods and set yourself a power target to avoid costly mistakes.

    ECU mapping should help to fully realize the full potential of all the parts you've done to your OM626.

    (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 may differs on the parts you've applied and the condition of your engine.

    It is the main goal to any car tuning task to feed more air into each cylinder

    Intake transmit the air during the suck phase from the air cleaner and allow it to be fed into the engine and mixed with fuel.

    Design and flow rate of the Intake can make a large difference to fuel delivery on the OM626.

    Commonly we find the intake are improved through performance upgrades, although a few makers provide well optimised intake.

    Larger OM626 valves, getting 3 or 5 angle valve jobs and porting and head flowing will also raise bhp and torque, the fantastic side effect is it will allow you to get a greater bhp and torque increase on other mods.

    OM626 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 OM626

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

    If a car has a turbo already fitted parts are more reliable and we find turbo engines are made with stronger components.

    However every engines have weakspots.It is important to find these limitations and install stronger pistons, crank and engine components to survive the power.

    It's not unheard of mechanics spending a fortune on turbocharger upgrades on the OM626 only to suffer the humiliation of seeing the whole thing go up in smoke just after it's used on the roads.

    Bigger turbo units often suffer a bottom end lag, and little turbo units spool up really quickly but won't have the peak end engines power gains.

    Thanks to new tech the selection of turbos is always evolving and we now see variable vane turbos, allowing the vane profile is altered according to speed to lower lag and increase top end torque.

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

    You'll commonly see there's a limit in the air flow sensor (AFM/MAF/MAP) on the OM626 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 power at a much lower level.

    Adding a supercharger or additional turbo will make large torque gains, although harder to install. We have this article covering twinchargers if you want to read more.


    When you raise the bhp and torque you will need to uprate to the fuel delivery.

    More bhp and torque needs more fuel. It makes sense to over specify your injector capacity.

    As a rule of thumb add 20% to the flow rate when fitting an injector, helps cope with injector deterioration and gives a bit of 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.

    OM626 Performance Exhausts

    You only need to upgrade your exhaust if your current exhaust is actually creating a restriction.

    On most factory exhausts you'll see the exhaust flow rate is ok 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 balance the flow of gases through the engine.

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

    Typically exhaust restrictions can be located the catalyst 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 OM626

    The OM626 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 OM626, 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 OM626 engine please join us in our car forums where you can discuss OM626 tuning options in more detail with our OM626 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 to hear what our visitors have got up to and which modifications 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 OM626 tuning guides which get regular updates and revisions.

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    One Response to “OM626 Tuning”

    1. Vasilis says:

      I have a mercedes w205 c180diesel probably with the renault om626 engine. I would like to upgrade the turbo, maybe with a hybrid, intercooler, full exhaust and whatever else is needed that I don’t know to go beyond 200 horses. What brands do you recommend I use without having a problem with the machine and what else will I need? how many horses could the car get? thank you

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