Modding uprating the Mercedes M155 engine!

Tuning guide "M155 Modifications"

M155 Modifications Guide

How to modify and upgrade the Mercedes M155

"Comprehensive guide to tuning the Mercedes M155 engine!"

Sites like TorqueCars are regularly seeing threads requesting info on how to improve the M155 from people wanting to know what are the ultimate M155 power upgrades. So let us look into Mercedes M155 upgrades and outline the best modifications on this great engine and point out some potential pitfalls along the way.

In this article we review M155 tuning and provide tips on the premier modifications for your car. Mercedes M155 really good project engines and with the right sports tuning mods like ECU maps, turbo improvements and camshafts you will substantially increase your driving opportunities.

The greatest M155 parts on an engine are in our opinion the ones that give the biggest return for your money.

We won't be swayed by popular M155 parts, they need to be cost effective.

M155 induction kits

Improving air intake on the M155

You need air and fuel for an engine to work. If there is insufficient fuel then it will run lean, if there is not enough air it runs rich resulting in lost 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 Getting air into your M155 is the whole point to any engine tuning project.

It is common that there is a limit in the air flow sensor AFM/MAF on the M155 when considerably more air is being pulled into the engine.

We note 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor sapped bhp at a much lower level.

Engines intake headers carry the on the suck phase from the filter and allow it to be fed into the engine cylinders.

Design and flow rate of the Intake headers can make a noticeable change to fuel mixing and power on the M155.

Commonly we find the intake manifold are improved through an upgrade, although some manufacturers provide reasonably good intake manifold.

Fitting big valve kits, carrying out port matching and head flowing will also raise performance, the fantastic side effect is it will make space for an improved performance increase on other parts.

M155 performance cam tips.

Some M155 engines respond better to mild camshaft durations so view each engine as unique.

The ECU mapping and fuel pump and injectors also will say much on the power gains you'll make.

A longer valve duration can alter the power 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.

The cam profile plays a big part in the engines power output so cam upgrades make quite a large difference. The intake & exhaust durations will alter depending on the chosen cam profile, so large bhp gains are on offer for cam upgrades.

NB: Fast road cams commonly push up the performance over the rev band, you could drop a little low end power but the high end rpm power will improve.

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

A Motorsport and race camshaft won't do well if driving in heavy traffic.

You should ideally match your torque band to your driving style so for a car used daily stick with a fast road M155 camshaft

Stage 1, 2 and 3 mods for the M155

Stage 1 M155 parts:

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

Stage 2 M155 parts:

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

Stage 3 M155 parts:

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

The M155 engines respond well to upgrades and we note that there are quite a few choices of upgrades and tuning parts about.

Remapping helps release the full potential of all the modifications you've done to your M155.

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 your mileage usually differs on the modifications you've applied and the condition of your engine.

Turbo modifications on the M155

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 M155.

The more air you can get into an engine, the more fuel it can burn and uprating the induction with a turbocharger upgrade makes major power gains.

When a car has forced induction upgrades are going to make more power and turbocharged engines will have more solid components.

There are reliable limits for every engine, with some being over specified and some only just able to handle stock power

It is important to find these limitations and upgrade to higher quality components to handle the power.

There are many car owners spending a lot of money on turbocharger upgrades on the M155 only to experience the motor throw a rod soon after it's first rolling road session.

Big upgraded turbo chargers commonly experience low end lag, and low capacity turbo chargers spool up much more quickly but do not have the top end power band gains.

Thanks to progress the choice of turbos is always improving and we now see variable vane turbos, permitting the vane angle is altered according to speed to lower lag and increase top end torque.

Twin scroll turbos divert the exhaust gases into two channels and direct these at differently designed vanes in the turbo charger. They also increase 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 harder to install. We have this feature on twinchargers if you want to read more.

Tips about fuel supply on the M155

You will need to ensure that the engine is not starved of fuel so need to increase the fuelling when you start going beyond 20% of a torque hike. We would recommend you to over specify your flow rate on the injectors.

The rule of thumb is to add 15% capacity when specifying an injector, this allows for injector deterioration and provides a bit of 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 M155 performance exhaust upgrades

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

On most factory exhausts you'll find the 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 out of the engine but do not go 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.

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

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

Faults issues and things to look out for on the M155

Like most engines an M155, 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 M155, failure to do this will exacerbate engine wear, on a tuned M155 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 M155 why not pop over to the forums at TorqueCars where you can chat about M155 tuning options and read about others projects who may be planning to do similar modifications on their M155.

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