Tuning the Mercedes M256

"Comprehensive guide to tuning the Mercedes M256 engine!"

We are regularly getting posts requesting information on the ultimate M256 power upgrades. So let us look into Mercedes M256 upgrades and outline the best mods that work on this great engine and point out some frequent tuning mistakes along the way.

Now we will review and look at M256 tuning and outline the optimum modifications for your car. Mercedes M256 offer good returns when tuned and with carefully picked tuning modifications like a remap, turbo upgrades and camshafts you will definitely improve your driving enjoyment.

Just because particular upgrades are popular with M256 owners it doesn't mean it is good, so we'll focus upgrades that will give your M256 the best power gain for you spend.

Significant gains on the M256 can be made from camshaft upgrades. Altering the camshaft profile alters the intake and exhaust durations on the engine and can dramatically change the bhp and power output.

NB: Fast road camshafts tend to increase the power through the rpm range, you may lose a little low end power but the higher rpm power will be lifted.

Race camshafts, increase the higher rpm power 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.

You should ideally optimize your bhp range to your preferences so for a road car stick with a mild fast road M256 cam

Each engine responds better to different camshaft durations check your engine on a rolling road.

The ecu map and injectors and fuel pump also will say much on the torque gains you'll get.

A longer valve duration 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.

M256 Tuning Stages

Stage 1 M256 modifications: Panel air filters, Intake headers, Sports exhaust manifold, Fast road camshaft, Remaps/piggy back ECU, Drilled & smoothed airbox.

Stage 2 M256 modifications: Ported and polished head, high flow fuel injectors, Fast road cam, Sports catalyst & performance exhaust, induction kit, fuel pump upgrades.

Stage 3 M256 modifications: Adding or Upgrading forced induction (turbo/supercharger), Internal engine upgrades (head flowing porting/bigger valves), Twin charging conversions, Competition cam, Crank and Piston upgrades to alter compression, Engine balancing & blueprinting.

The M256 units make great tuning projects and we're pleased to see that there is a lot of parts and tuning parts around.

A remap should help to release the full potential of all the mods you've done to your M256.

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

It is the whole point to any car tuning job to shove more fuel and air into your M256

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

Structure and flow rate of the Headers can make a large improvement to fuel mixing and power on the M256.

I usually find headers are ripe for motorsport parts, although a few makers provide fairly well optimized headers.

Adding a M256 larger valve kit, carrying out 3 or 5 angle valve jobs and porting and head flowing will also raise power, & importantly will give you raising the power increase on other tuning mods.

Turbo upgrades for the M256

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 M256

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.

When your motor has a turbocharger tuning parts are giving better power gains and you'll see that turbocharged engines are made with uprated components.

There are weak spots for every engine, with some being over specified and some just sufficiently able to handle stock power

Discover these restrictions and fit stronger pistons, crank and engine components to cope with the power.

We see many car owners spending a loads on turbo upgrades on the M256 only to see the car explode soon after it's finished.

Large upgraded turbochargers often experience low end lag, and low capacity turbochargers spool up more quickly but do not have the peak end engines power gains.

Over the last 20 years the selection of turbochargers is always moving on and we commonly find variable vane turbochargers, allowing the vane angle is altered according to speed to lower lag and increase top end performance.

Twin scroll turbochargers divert the exhaust gases into 2 channels and feed these at differently designed vanes in the turbo charger. They also boost the scavenging effect of the engine.

It is common that there is a restriction in the air flow sensor AFM/MAP on the M256 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 limited torque at a much lower level.

Adding a supercharger or additional turbo will make large performance gains, although more difficult to configure. We have this in depth look at twinchargers if you want to read more.

Uprating M256 fuel injectors

Don't omit to improve the fuel delivery when you are increasing the bhp - it makes the car more thirsty. Don't forget to be generous with your injector capacity.

As a rule of thumb add 20% capacity when buying an injector, helps cope with injector deterioration and allows a little 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 M256 performance exhausts

You may need to boost your exhaust if your exhaust is actually creating a flow problem.

On most factory exhausts you'll find the 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 generally help improve air flow out of 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.

Common exhaust restrictions are in the catalyst and filters installed, so adding a faster flowing high performance alternative will help avoid this restriction.

Problems and issues to look out for on the M256

The M256 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the M256, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your M256 engine please join us in our friendly forum where you can discuss tuning options in more detail with our M256 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 mods were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our M256 guides and tips are kept up to date.

Please Check out my YouTube channel, we're regularly adding new content...

PLEASE HELP: I NEED YOUR DONATIONS TO COVER THE COSTS OF RUNNING THIS SITE AND KEEP IT RUNNING. I do not charge you to access this website and it saves most TorqueCars readers $100's each year - but we are NON PROFIT and not even covering our costs. To keep us running PLEASE Donate here

If you liked this page please share it with your friends, drop a link to it in your favourite forum or use the bookmarking options to save it to your social media profile.

Feedback - What do You Think?

Please use our forums if you wish to ask a tuning question, and please note we do not sell parts or services, we are just an online magazine.

Help us improve, leave a suggestion or tip

Your Constructive comments on this article, I really want to improve this article with your help and suggestions.


Please watch this video and subscribe to my YouTube channel.



Member Benefits

Join our forum today and benefit from over 300,000 posts on tuning styling and friendly car banter.

You will also have full access to the modifed car gallery, project car updates and exclusive member only areas.

(All car owners of all ages and from all countries are welcome).