Mercedes M104 Tuning

"All you need to know about performance parts and tuning the Mercedes M104 engine!"

The Mercedes M104 engine is an inline-six cylinder gasoline engine produced by Mercedes-Benz from 1989 to 1999.

It is part of the M100/M103/M104 engine family and was used in various Mercedes-Benz models during its production period along with SsangYong and other lesser known car maker.

The M104 engine is an inline-six cylinder engine, which means it has six cylinders arranged in a single row. This configuration is known for its smoothness and balance.

The engine came in various displacements over its production years, including 2.8 liters, 3.0 liters, and 3.2 liters. A 3.4 and 3.6 liter version was offered by AMG, and the setup they have created is an inspiration and shows how flexible and the potential the M104 engine has.

The M104 engine was known for its performance characteristics, especially in higher-displacement versions. It offered good power output and torque, making it suitable for a range of Mercedes-Benz vehicles.

The M104 engine featured advanced technology for its time, including double overhead camshafts (DOHC) and four valves per cylinder. This design allowed for improved airflow and higher engine efficiency.

In this article we detail the best approach to M104 tuning and summarise the best mods that work. Mercedes M104 make a good tuning project and with carefully chosen sports modifications like remapping, turbo upgrades and camshafts you will substantially increase your driving opportunities.

History, Power & Specs of the Engine

M104 2.8 L M104.900

3.0 L M104.98x

  • 217 to 228 hp@ 6400 rpm 265Nm (195lbft@ 4600) (with cat)
  • 220 to 231 PS@ 6400 rpm Torque  269Nm (199lbft@ 4600)

Models Using these engines...

  • 1989–1992 C124 300 CE-24
  • 1989–1993 R129 300SL-24
  • 1990–1993 W124 300 E-24
  • 1990–1993 T124 300 TE-24

2.8 L M104.94x

Engine power @ 5500 rpm: (258 PS; 255 hp) Torque @ 3750 rpm: 270Nm (199lbft)

  • W202 C280
  • W210 E280
  • 1993–1994 W124 280 E, 300 E 2.8
  • 1993–1998 W140 300 SE 2.8, S 280
  • 1994–1996 W124 E 280

3.2 L M104.99x

(231 PS; 228 hp @ 5500 rpm) 255Nm (188lbft) @ 4400 rpm

  • 1991–1993 W140 300 SE, 300 SEL
  • 1993–1999 W140 S320
  • 1993–1994 W124 300 E, 320 E
  • 1994–1996 W124 E 320
  • 1994–1998 R129 SL 320
  • 1995–1997 W210 E320
  • W463 G320


  • Kyron
  • 1993–1999 Musso
  • 1997-2006 Chairman
  • Korando
  • 2001–2006 Rexton Y200

AMG 3.4 L

  • (364 PS; 359 hp) @ 6500 rpm  268Nm (198lbft) @ 4500 rpm

AMG 3.6 L M104.941/M104.992

  • M104 was rated@276 hp (; 280 PS) @5,750 rpm and 284lbft (385 Nm)

Tuning the Mercedes M104 and best M104 performance parts.

Best M104 tuning parts

Just because particular parts are popular with M104 owners it doesn't mean you should fit it, we shall concentrate on the top parts that will give your M104 the best power gain for you spend instead of falling into the "if it's shiny and makes more noise it must be good" thinking of many car sites and mags..

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

Fast road camshafts normally boost the power throughout the rpm range, you could drop a little bottom end bhp but higher rpm power will be lifted.

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

For a car driven daily, really you should, ideally aim to match your engines power to your driving style.

You will never have ever thought or claimed that a M104 Competition cam is a pleasure to live with when 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.

Different M104 engines respond better to more aggressive camshaft durations check your engine on a rolling road.

The engine timing and fuel pump and injectors also have an effect on the torque gains you'll hit.

Altering valve durations can alter the torque 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.

Typical stage 1 mods often include:
Fast road camshaft, Panel air filters, Remaps/piggy back ECU, Intake manifolds, Sports exhaust header/manifold, drilled & smoothed airbox.

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

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

Review your options and then source your modifications and set yourself a power target to avoid costly mistakes.

Remaps allows a tuner to unlock the full potential of all the mods you've done to your M104.

(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 mods you've applied and the condition of your engine.

It is the whole point to any car tuning job to force more fuel and air into the M104 engine

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

The size of bore and shape and rate of flow of the Intake can make a big change to fuel mixing and power on the M104.

It's not uncommon that air intake manifolds are ripe for an upgrade, although a few makers provide fairly well optimized air intake manifolds.

Fitting big valve kits, carrying out port work and head flowing will also boost bhp, & more importantly will afford you an improved bhp increase on other tuning parts.

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 M104

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

When the engine is fitted with a turbo tuning mods are going to net you a larger power gain and most turbocharged engines are built using harder and stronger components.

There are common areas of failure for every engine, with some being over specified and some only just able to handle stock power

Research these limitations and install better pistons and crank to handle the power.

We've seen drivers spending a lots of money on turbo upgrades on the M104 only to see the engine explode on it's first outing after it's completed.

Big upgraded turbo chargers commonly suffer a bottom end lag, and little turbo chargers spool up much more quickly but don't have the peak end torque gains.

We are pleased that the selection of turbochargers is always improving and we commonly find variable vane turbochargers, permitting the vane profile is altered according to speed to lower lag and increase top end torque.

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

You'll commonly see there is a limit in the air flow sensor AFM/MAP on the M104 when considerably 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 was restricting torque at a much lower level.

Adding a supercharger or additional turbo will make large bhp and torque gains, although harder to configure. We have this guide to twinchargers if you want to read more.


When you raise the torque you will need to pay attention to the fuelling.

More torque needs more fuel. Don't forget to over specify your injectors flow rate.

The rule of thumb is to add 20% when fitting an injector, helps cope with injector deterioration and allows you 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.


You may need to boost your exhaust if the existing exhaust is actually causing a restriction.

On most factory exhausts you should find that the 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.

Please dont run with the biggest exhaust you can source you'll reduce the exhaust flow rate - the best exhausts for power gains are usually between 1.5 to 2.5 inches. It is the shape and material more than the bore size.

Usual exhaust restrictions can be located the emissions filters installed, so adding a better 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 M104

The M104 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.

It was designed to potentially reach high mileage, with some drivers reporting up to 230,000 miles without major issues. Maintenance, quality oil, and care are crucial for its performance, similar to other engines.

Overall, the M104 engine is considered reliable compared to other engines of its time, despite a few recurring problems.

Mass airflow sensor failure is common, affecting engine performance and power.

Oil leaks are also reported, possibly caused by worn gasket seals and valve stems.

Overheating due to cooling fan and radiator issues is a significant concern.

Symptoms of these issues include smoke, overheating, oil puddles, and reduced engine power. The M104 engine's reliability is rated as very good, but it's sensitive to cold climates and requires diligent maintenance to mitigate potential problems.

While the M104 engine has weaknesses, like its fuel system, sensors, and computers, it strikes a balance between durability and power. Enthusiasts appreciate it as one of the notable engines from Mercedes, despite its minor imperfections.

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 M104, 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 M104 engine please join us in our friendly forum where you can discuss tuning options in more detail with our M104 owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

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