Discover "M256 Modifications"

How to modify and upgrade the Mercedes M256

"Comprehensive guide to tuning and performance parts on the Mercedes M256 engine!"

TorqueCars are frequently seeing threads asking how to improve the M256 from people inquiring about getting more power from the M256 and wanting to know what are the best M256 modifications. So let us look into Mercedes M256 tuning mods and outline the best modifications on this great engine and point out some potential pitfalls along the way.

Now we will look at M256 tuning and provide tips on the greatest modifications. Mercedes M256 are good project engines and with a few sensible modified enhancements like remapping, turbo kits and camshafts you will definitely maximise your driving fun.

The optimum M256 parts on an engine are typically the ones that give the best gains for your money.

We won't be swayed by popular M256 parts, they need to be cost effective.

Improving air intake on the M256

You need fuel and air for an engine to work. If there is insufficient fuel then it will run lean, if there is not enough air it runs rich losing power . We'll pick up on fuelling later in this article but for now we shall look at air supply.

So the primary aim to any performance tuning project to pull fuel and air into the M256 engine but this has a knock on effect with the air flow sensor.

It is common that there is a limitation in the air flow sensor (AFM/MAF/MAP) on the M256 when considerably more air is being fed into the engine.

We see 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor was restricting performance at a much lower level.

The intake plenum carry the air during the suck phase from the air cleaner and allow it to be pulled into the engine cylinders with fuel for the squish phase.

Design and flow characteristics of the Air Intake manifolds can make a noticeable improvement to fuel delivery on the M256.

We often see air intake manifolds are in dire need of an upgrade, although some car makers provide reasonably good air intake manifolds.

Adding a M256 larger valve kit, doing some port work and head flowing will also raise bhp, and significantly will make space for an improved bhp increase on other tuning parts.

M256 performance cam tips.

Each engine responds better to different camshaft durations than others.

The ECU mapping and fuelling also have an effect on the bhp gains you'll achieve.

Extending exhaust or intake 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.

Significant air intake, and exhaust improvements on the M256 can be made from cam upgrades. Changing the cam profile alters the intake and exhaust durations on the engine and can dramatically change the bhp and power output.

NB: Fast road camshafts normally raise the bhp throughout the rev band, you might lose a little low down torque but higher rpm power will be lifted.

Motorsport and race camshafts, raise 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 you need to match your torque band to your usage of the car.

I'd be shocked if you find a M256 Race camshaft is a pleasure to live with when driving in heavy traffic.

Stage 1, 2 and 3 mods for the M256

Before we break the best tuning upgrades down into stages of tune, let's list the most effective tuning upgrades for you.

1. Suspension Upgrades - always improve your cars handling
2. Brake Upgrades - Even before adding power improve those brakes
3. Intake - make sure the intake is not restricted, use filters and intake upgrades to improve this
4. Exhaust - as with 3 ensure there is not restriction in the exhaust, cats are the usual bottleneck
5. Tunes - remapping, piggyback ECU's and aftermarket ECU's can all make decent gains
6. Fuelling - when you've increased power you'll need to match this with more fuel
7. Turbo upgrades - Improving the intake with a large turbo and better flowing intercooler will be the biggest power gain you'll see (but one of the most complex).

This video guide to tuning cars is a great starting point to work from in your project.

Stage 1 M256 parts:

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

Stage 2 M256 parts:

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

Stage 3 M256 parts:

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

ECU flashing will help release the full potential of all the upgrades you've done to your M256.

You will typically expect to see gains of approximately 20-30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but power output may depend much on the upgrades you've applied and the condition of your engine.

Turbo modifications on the M256

To get a turbo working on a NASP engine there is a lot involved, from lowering compression ratio to improved fuel supply and mapping, so we have found a great guide to helpavoid the common pitfalls or end up with an unfinished project because you were not told what you were getting into by doing this on the 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 superb power gains.

When your car has a turbo already fitted parts are going to make more power and you'll see that turbocharged engines are built using better components.

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

See where you'll find these restrictions and upgrade to better quality crank and pistons to cope with the power.

It's not unheard of drivers spending a loads on turbocharger upgrades on the M256 only to have the motor literally blow up when it's first rolling road session.

Larger upgraded turbochargers commonly experience low end lag, and smaller turbochargers spool up really quickly but won't have the top end bhp gains.

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

Twin scroll turbochargers divert the exhaust gases into a couple of channels and direct these at differently angled vanes in the turbo charger. They also improve the scavenging effect of the engine.

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large performance gains, although harder to install. We have this in depth look at twinchargers if you want to read more.

Tips about fuel supply on the M256

You will need to ensure that the engine is not starved of fuel so must ramp up the fuelling when you start going beyond 20% of a performance hike. We would recommend you to over specify your injector capacity.

The accepted safe increase is to add another 20% when buying an injector, which takes into account injector deterioration and allows you some spare capacity should the engine need more fuel.

Don't forget that different fuel grades will usually require different settings, a high octane fuel will burn more efficiently than lower octane fuel for example. A car will trim fuel supply to keep within the ideal air fuel mix but at the extreme ends you may need to adjust your injector capacity, or the mapping or you'll get flat spots and potential lean or rich fuel issues..

Recommended M256 performance exhaust upgrades

You only need to to increase your exhaust system with an upgraded one is if the existing exhaust is creating a flow problem.

On most factory exhausts you'll find the exhaust flow rate is still fine even on modest power gains, but on a serious tuning project with a big boost in power you will certainly need to get a better flowing exhaust.

Sports exhausts generally help improve air flow from the engine but avoid an exhaust that is too large or you may end up will reduce the flow rate. Stick to one and a half to two and half inches as a rule of thumb.

The usual suspects causing problems in your exhaust flow rate come around the catalyst and filters installed, so adding a better flowing race alternative will help avoid this restriction.

Decats (NB:catalysts reduce harmful engine emissions) is illegal in most countries and regions.

Faults issues and things to look out for on the M256

Like most engines an M256, should have few issues if it gets properly serviced and looked after.

We cannot stress enough the need for oil changes with the correct grade of oil on the M256, failure to do this will exacerbate engine wear, on a tuned M256 this is more important than ever and close attention should be paid to your maintenance schedule.

If you are interested in learning more or getting impartial tuning advice for your M256 why not pop over to the forums at TorqueCars where you can chat about M256 tuning options and read about others projects who may be planning to do similar modifications on their M256.

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This entry was posted under Makes and Models. Tags: engine, mercedes
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