Modding uprating the Mercedes M103 engine!

Tuning guide "M103 Modifications"

M103 Modifications Guide

How to modify and upgrade the Mercedes M103

"Comprehensive guide to performance tuning the Mercedes M103 engine!"

Our friends at TorqueCars are always getting messages asking how to improve the M103 from people wanting to know what are the best tips on M103 modifications. So let us look into Mercedes M103 parts and outline the best upgrades on this great engine and point out some problems along the way.

Therefore we outline options for your M103 tuning and summarise the best modifications for your car. Mercedes M103 are popular engines and with the right uprated parts like remapping, turbo improvements and camshafts you will definitely improve your driving pleasure.

When talking about the greatest parts for your M103 engine, we are going to concentrate on the tuning mods that give the best power gain for you money.

M103 induction kits

Improving air intake on the M103

You need air and fuel for an engine to work. If there is a lack of fuel then it will run lean, if there is little flow of air it runs rich losing power and potentially damaging the engine. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So Feeding air and fuel into each cylinder is the primary aim to any car tuning task.

You'll commonly see there's a limitation in the air flow sensor AFM/MAP on the M103 when considerably more air is being pulled 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 bhp and torque at a much lower level.

Intake manifolds take the air from the filter and allow it to be fed into the engine and mixed with fuel.

Shape and flow rate of the air Intake manifold can make a noticeable change to fuel engine efficiency on the M103.

Most headers are begging for aftermarket parts, although a few manufacturers provide well optimised headers.

Larger M103 valves, getting port work and head flowing will also lift performance, & more importantly will make space for raising the performance increase on other mods.

M103 performance cam tips.

Some M103 engines respond better to more aggressive cam durations than others.

The ecu map and fuelling also will make differences on the torque gains you'll achieve.

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.

Significant air intake, and exhaust improvements on the M103 can be made from camshaft upgrades. Changing the camshaft profile alters the intake and exhaust durations on the engine and can dramatically change the torque and power output.

NB: Fast road cams commonly bump the power across the rev band, you could drop a little bottom end torque but your high end rpm power will be lifted.

Motorsport and race cams, bump the high end rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

In a road car you must carefully try to match your power band to your typical driving style.

I would be surprised if you have ever thought a M103 Race camshaft is a pleasure to live with when driving around busy urban areas.

Stage 1, 2 and 3 mods for the M103

Stage 1 M103 parts:

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

Stage 2 M103 parts:

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

Stage 3 M103 parts:

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

The M103 engines are great to work on and we see that there are plenty of parts and performance parts about.

Mapping helps fully realize the full potential of all the parts you've done to your M103.

Tuning tips and articles Engine tuning Transmission tuning Care care Intake & exhaust mods Improve handling Forums

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 end result may rely on the parts you've fitted and the condition of your engine.

Turbo modifications on the M103

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 M103.

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 has a turbo already fitted upgrades are simpler to install and we find turbo engines use stronger components.

However every engines have limits

See where you'll find these restrictions and fit higher quality crank and pistons to handle the power.

We see many guys spending a loads of money on turbo charger upgrades on the M103 only to suffer the humiliation of seeing the engine explode just after it's first rolling road session.

Big upgraded turbo units often experience low end lag, and little turbo units spool up much more quickly but do not have the peak rpm torque gains.

Thankfully the range of turbo chargers is always moving on and we are seeing variable vane turbo chargers, permitting 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 two channels and feed these at differently designed vanes in the turbo charger. They also help the scavenging effect of the engine.

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

Tips about fuel supply on the M103

When you raise the torque you will need to uprate to the fuelling.

More torque needs more fuel. Care modifiers usually say to be generous with your flow rate on the injectors.

The accepted safe increase is to add another 15% when buying an injector, which takes into account injector deterioration and affords 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 M103 performance exhaust upgrades

You should look to boost your exhaust system with an upgraded one is if your current exhaust is creating a restriction.

On most factory exhausts you'll find the exhaust 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 increase the flow of air through the engine.

But if the exhaust pipe is too big, ie: it's over two and a half inches diameter, you will lose a great deal of the flow rate and end up lacking power and torque.

The usual suspects causing problems in your exhaust flow rate can be located the catalyst and filters installed, so adding a freer flowing race 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 M103

Like most engines an M103, 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 M103, failure to do this will exacerbate engine wear, on a tuned M103 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 M103 why not pop over to the forums at TorqueCars where you can chat about M103 tuning options and read about others projects who may be planning to do similar modifications on their M103.

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