Tuning the Mercedes M104

"Comprehensive guide to tuning the Mercedes M104 engine!"

We are regularly getting emails asking how to improve the M104 from people wanting to know what are the ultimate M104 upgrades. So let us look into Mercedes M104 upgrades and outline the best mods that work on this great engine and point out some common pitfalls along the way.

The Mercedes M104 make a good tuning project and with a few sensible uprated tuning mods like a remap, turbo kits and camshafts you will substantially maximise your driving enjoyment.

In this article we look at M104 tuning and outline the ultimate modifications for your car.

When talking about the best parts for your M104 engine, we are going to focus on the upgrades that give the best power gain for you money.

Altering your M104 camshaft will make a dramatic difference to the engine power band. Choosing a higher performance camshaft profile raises the power band accordingly.

NB: Fast road camshafts commonly bump the power through the rpm range, you could sacrifice a little bottom end bhp but the top end will be higher.

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

In a road car must carefully try to match your bhp range to your preferences.

I'd be shocked if you have found a M104 Motorsport camshaft is a pleasure to live with when driving around busy urban areas.

Different M104 engines respond better to different cam durations so view each engine as unique.

The engine timing and fuelling 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.

M104 Tuning Stages

Stage 1 M104 modifications: Sports exhaust manifold, Intake headers, Panel air filters, Fast road camshaft, Drilled & smoothed airbox, Remaps/piggy back ECU.

Stage 2 M104 modifications: fuel pump upgrades, Fast road cam, Sports catalyst & performance exhaust, Ported and polished head, induction kit, high flow fuel injectors.

Stage 3 M104 modifications: Internal engine upgrades (head flowing porting/bigger valves), Competition cam, Adding or Upgrading forced induction (turbo/supercharger), Engine balancing & blueprinting, Crank and Piston upgrades to alter compression, Twin charging conversions.

Mapping will help unlock the full potential of all the parts you've done to your M104.

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but the end result often differs on the parts you've fitted and the condition of your engine.

It is the aim to any engine performance tuning task to pull more air and fuel into each cylinder

Headers take the air from the intake filter and allow it to be sucked into the engine cylinders with fuel for the squish phase.

Structure and flow rate of the Intake manifold can make a substantial change to fuel atomisation on the M104.

Commonly we find the plenum chambers are improved through performance upgrades, although a few OEM provide decently flowing plenum chambers.

Larger M104 valves, getting port matching and head flowing will also increase power, and importantly will give you increasing the power increase on other upgrades.

Turbo upgrades for the M104

NASP 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 massive power gains.

If the engine has a turbocharger mods are going to net you a larger power gain and most turbo charged engines already contain uprated components.

There are common areas of failure for every engine, with some being incredibly solid and some just sufficiently able to handle stock power

Research these limits and fit better quality components to survive the power.

We see many drivers spending a loads on turbocharger upgrades on the M104 only to watch the M104 literally blow up soon after it's been finished.

Big capacity turbos tend to experience no power at low rpm, and little turbos spool up more quickly but don't have the peak rpm power band gains.

In the last 10 years the range of turbos is always improving and we now see variable vane turbos, where the vane angle is altered according to speed to lower lag and increase top end performance.

Twin scroll turbos divert the exhaust gases into a couple of channels and flow 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 limitation in the air flow sensor (AFM/MAF/MAP) on the M104 when loads more air is being sucked into the engine.

Going up you'll find 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 gains, although more challenging to install. We have this feature on twinchargers if you want to read more.

Uprating M104 fuel injectors

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

The accepted safe increase is to add 20% to the flow rate when fitting an injector, this allows for injector deterioration and provides 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.

Best M104 performance exhausts

You may need to replace your exhaust if your exhaust is actually causing a flow problem.

On most factory exhausts you'll find 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.

Sports exhausts can usually air flow through the engine but avoid an exhaust that is too large or you could will reduce the flow rate. Stick to 1.5 to 2.5 inches for best results.

Usual exhaust restrictions come around the filters installed, so adding a better flowing race alternative will help avoid this restriction.

Problems and issues to look out for on the M104

The M104 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the M104, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information 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.

We need your help to complete and improve this page, so do give us your feedback in the comments box below.

We really like hearing from our readers, and hearing about which upgrades were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our M104 guides and tips are kept up to date.

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This article is flagged for an update, so please pass on specific tips below that I can include. All articles, and content was written by me, Waynne Smith TorqueCars founder. Some outlines are just too general so I appreciate your feedback and suggestions. This entry was filed under Mercedes. You can leave a response below or join our forum to discuss this article and car modification in detail with our members.

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