Everything You Need To Know About "M281 Modifications"

How to modify and upgrade the Mercedes M281

"Comprehensive guide to tuning the Mercedes M281 engine!"

Popular tuning sites like TorqueCars are regularly getting posts requesting information on how to improve the M281 from people wanting to know what are the ultimate M281 power upgrades. So let us look into Mercedes M281 parts and outline the best modifications on this great engine and point out some potential pitfalls along the way.

Here we look into M281 tuning and report on the ultimate upgrades. Mercedes M281 provide a fun base for your project and with the right tuning tuning mods like ECU maps, turbo upgrades and camshafts you will increase your driving fun.

Just because particular mods are are common on M281 it doesn't mean you should fit it, so we'll concentrate on the optimum mods that will give your M281 the best power gain for you spend.

Without us subscribing to the misaprehension of 'if it's shiny and makes more noise it must be good' you seem to get in many tuning magazines and on car forums'.

Improving air intake on the M281

You need air matched to fuel for an engine to work. If there is a lack of fuel then it will run lean, if there is insufficient 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 engine upgrade job to force more fuel and air into each cylinder but this has a knock on effect with the air flow sensor.

You'll commonly see there's a limitation in the air flow sensor MAP/MAF/AFM on the M281 when considerably more air is being drawn into the engine.

When tuning you may well find you need to get an air sensor or flow meter capable of upto 4 bars to cope with quite large power gains, whereas the OEM air sensor was restricting torque at a much lower level.

Air Intake manifolds flow the during the engines suck phase from the filter and allow it to be drawn into the engine cylinders with fuel for the squish phase.

Structure and flow rate of the Plenum can make a substantial improvement to fuel delivery on the M281.

On popular production engines intake headers are begging for a performance upgrade, although some makers provide reasonably good intake headers.

Increasing the M281 valve size, getting port matching and head flowing will also improve bhp and torque, the fantastic side effect is it will raise potential for a better bhp and torque increase on other upgrades.

M281 performance cam tips.

Different M281 engines respond better to mild camshaft durations so view each engine as unique.

The map and injectors and fuel pump also have a large bearing on the bhp gains you'll hit.

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.

Significant air intake, and exhaust improvements on the M281 can be made from camshaft upgrades. Changing the camshaft profile alters the intake and exhaust durations on the engine and can dramatically change the power band and power output.

NB: Fast road camshafts tend to boost the performance across the rev band, you might lose a little low end power but higher rpm power will be higher.

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

A Race camshaft is not great driving in heavy traffic.

You should ideally match your power band to your typical driving style so for a daily driver stick with a shorter duration M281 camshaft

Stage 1, 2 and 3 mods for the M281

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 M281 parts:

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

Stage 2 M281 parts:

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

Stage 3 M281 parts:

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

ECU flashing will help unlock the full potential of all the tuning parts you've done to your M281.

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 the outcome may differs on the tuning parts you've fitted and the condition of your engine.

Turbo modifications on the M281

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 M281.

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.

When your car has a turbo already fitted parts are simpler to install and most turbo engines are made with better components.

However you will find an engines will need better parts at higher power limits

Discover these limits and fit better pistons and crank to survive the power.

There are many car owners spending a lot of money on turbo charger upgrades on the M281 only to suffer the humiliation of seeing the M281 catastrophically fail soon after it's finished.

Larger upgraded turbo chargers tend to experience low end lag, and smaller turbo chargers spool up much more quickly but don't have the peak rpm bhp gains.

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

Twin scroll turbo chargers divert the exhaust gases into 2 channels and feed these at differently profiled vanes in the turbocharger. 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 bhp gains, although more challenging to configure. We have this article covering twinchargers if you want to read more.

Tips about fuel supply on the M281

You will need to ensure that the engine is not starved of fuel so should uprate the fuelling when you start exceeding 20% of a bhp hike. It makes sense to over specify your injectors flow rate.

The accepted safe increase is to add 20% capacity when fitting an injector, this allows for injector deterioration and provides you some spare capacity should the engine require 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 M281 performance exhaust upgrades

You only need to to upgrade your exhaust system with an upgraded one is if the existing exhaust is actually causing a restriction.

On most factory exhausts you should find that your flow rate is 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 will certainly help air flow through the engine but avoid an exhaust that is too wide 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.

Typically exhaust restrictions come around the filters installed, so adding a freer flowing sports alternative will help avoid this restriction.

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

Faults issues and things to look out for on the M281

Like most engines an M281, 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 M281, failure to do this will exacerbate engine wear, on a tuned M281 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 M281 why not pop over to the forums at TorqueCars where you can chat about M281 tuning options and read about others projects who may be planning to do similar modifications on their M281.

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