Mercedes M273 Tuning

"All you need to know about performance parts and tuning the Mercedes M273 engine!"

We shall examine the options for your M273 tuning and show the ultimate modifications. Mercedes M273 are popular tuning projects and with carefully chosen uprated enhancements like remapping, turbo kits and camshafts you will definitely improve your driving experience.

History, Power & Specs of the M273 Engine


M273 E47 4.7 L

  • 340 PS 335 hp at 6000 rpm 460 Nm 339lbft at 2700-5000 rpm.

2007–2012 GL450
2007–2013 S450
2007–2011 ML450

M273 E55 5.5 L

  • 387 PS 382 hp at 6000 rpm 530 Nm 391lbft at 2800-4800 rpm.

2006–2011 E500/E550
2006–2010 CL500/CL550
2006–2010 CLS500/CLS550
2006–2012 GL500/GL550
2008-2011 ML500/ML550
2006–2009 S500/S550
2007-2012 SL500/SL550
2006–2009 CLK500/CLK550

Tuning the Mercedes M273 and best M273 performance parts.

Best M273 upgrades

When talking about the best modifications for your M273 engine, we are going to focus on the mods that give the biggest return for your cash.

Altering your M273 cam will make a dramatic difference to the engine torque. Choosing a higher performance cam profile raises the torque accordingly.

Fast road camshafts usually increase the torque throughout the rpm band, you may sacrifice a little bottom end power but top end will be higher.

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

A Motorsport and race cam is not great 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 power band to your cars usage so for a car used daily stick with a shorter duration M273 cam

Different M273 engines respond better to more or less aggressive cam durations than others.

The map and fuel pump and injectors also will make differences 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:
    Intake manifolds, Fast road camshaft, Sports exhaust header/manifold, drilled & smoothed airbox, Panel air filters, Remaps/piggy back ECU.

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

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

    Carefully think through your options and then acquire your tuning parts and set yourself a power target to save yourself from expensive mistakes.

    Remaps helps to establish the full potential of all the upgrades you've done to your M273.

    (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 mileage usually rely on the upgrades you've fitted and the condition of your engine.

    It is the main goal to any engine upgrade project to push fuel and air into your M273

    The intake plenum flow the air during the suck phase from the intake filter and allow it to be drawn into the engine cylinders with fuel for the squish phase.

    The size of bore and shape and flow rate of the Intake manifold can make a noticeable improvement to fuel mixing and power on the M273.

    It's not uncommon that intake manifolds are ripe for performance upgrades, although some car makers provide reasonably well designed intake manifolds.

    Increasing the M273 valve size, getting port work and head flowing will also raise power, and more importantly will make space for a better power increase on other tuning mods.

    M273 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 M273

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

    If a car is fitted with a turbo mods are relatively easy and you will discover turbo engines are built with many forged and stronger components.

    However you will find engines will have power limits.We recommend you find these limitations and install better pistons and crank to survive the power.

    We see many car owners spending a fortune on turbocharger upgrades on the M273 only to suffer the humiliation of seeing the motor literally blow up just after it's first rolling road session.

    Bigger turbos tend to experience no power at low rpm, and little turbos spool up much more quickly but don't have the peak end engines power gains.

    In the last 10 years the selection of turbos is always increasing and we now see variable vane turbos, allowing the vane profile is altered according to speed to lower lag and increase top end bhp and torque.

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

    You'll commonly see there's a limit in the air flow sensor (AFM/MAF/MAP) on the M273 when considerably more air is being drawn into the engine.

    Going up you'll find 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor sapped bhp at a much lower level.

    Adding a supercharger or additional turbo will make large performance gains, although more difficult to install. We have this feature on twinchargers if you want to read more.


    You will need to ensure that the engine is not starved of fuel so need to ramp up the fuelling when you start exceeding 20% of a power increase.We strongly recommend you to be generous with your injectors flow rate.

    As a rule of thumb add 20% to the flow rate when fitting an injector, this allows for injector deterioration and affords some 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.

    M273 Performance Exhausts

    You only need to increase your exhaust if your current exhaust is actually creating a flow problem.

    On most factory exhausts you'll see 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.

    Don't go with the biggest exhaust you can buy you'll reduce 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.

    Typically exhaust restrictions can be located the filters installed, so adding a freer flowing sports alternative is the answer. This keeps the car road legal and will flow much better due to it's higher internal surface area and design, so has the added benefit of keeping your car road legal. The alternative decat should be considered an off road only mod, as removing a catalyst is illegal in most territories and regions for road registered cars..

    Weak spots, Issues & problem areas on the M273

    The M273 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 M273, 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 M273 engine please join us in our car forums where you can discuss M273 tuning options in more detail with our M273 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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