Tuning the Mercedes M155

"Comprehensive guide to tuning the Mercedes M155 engine!"

We are regularly getting posts about the premier M155 modifications. So let us look into Mercedes M155 parts and outline the best mods that work on this great engine and point out some common pitfalls along the way.

The Mercedes M155 really good project engines and with the right tuning tuning mods like remapping, turbo upgrades and camshafts you will certainly increase your driving fun.

This pages aim is examine the options for your M155 tuning and point out the optimum mods that work.

The greatest M155 tuning mods on an engine are in our opinion the ones that give the best value for money.

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

Significant gains on the M155 can be made from cam upgrades. Altering the cam profile alters the intake and exhaust durations on the engine and can dramatically change the torque and power output.

NB: Fast road camshafts usually boost the performance across the rev band, you could sacrifice a little bottom end bhp but top end will be lifted.

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

A Competition camshaft won't do well if on the daily commute.

You should ideally match your bhp range to your driving style so for a daily driver stick with a mild fast road M155 camshaft

Each engine responds better to different cam durations so set your engine up on a rolling road.

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

Longer valve durations 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.

M155 Tuning Stages

Stage 1 M155 modifications: Sports exhaust manifold, Intake headers, Panel air filters, Drilled & smoothed airbox, Fast road camshaft, Remaps/piggy back ECU.

Stage 2 M155 modifications: high flow fuel injectors, induction kit, fuel pump upgrades, Sports catalyst & performance exhaust, Ported and polished head, Fast road cam.

Stage 3 M155 modifications: Internal engine upgrades (head flowing porting/bigger valves), Engine balancing & blueprinting, Adding or Upgrading forced induction (turbo/supercharger), Twin charging conversions, Crank and Piston upgrades to alter compression, Competition cam.

Remaps should help to release the full potential of all the tuning mods you've done to your M155.

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

It is the whole point to any engine modification project to force more air into each cylinder

The intake plenum take the air during the suck phase from the air filter and allow it to be drawn into the engine and mixed with fuel.

The shape and flow rate of the Headers can make a big effect on to fuel delivery on the M155.

It's not uncommon that air intake manifolds are improved through performance upgrades, although some car makers provide reasonably good air intake manifolds.

Increasing the M155 valve size, doing a bit of M155 port enlargement and head flowing will also increase bhp, & more importantly will afford you a better bhp increase on other parts.

Turbo upgrades for the M155

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 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.

If your motor is fitted with a turbo upgrades are more reliable and turbocharged engines are made with more solid components.

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

Research these restrictions and upgrade to forged components to handle the power.

We see many mechanics spending a lots of money on turbo charger upgrades on the M155 only to see the engine block explode on it's first outing after it's used in anger.

Large turbos often experience a bottom end lag, and little turbos spool up quickly but do not have the top end bhp gains.

Thankfully the range of turbos is always developing and we are seeing variable vane turbos, allowing the vane angle is altered according to speed to lower lag and increase top end power.

Twin scroll turbos divert the exhaust flow into two channels and flow these at differently angled vanes in the turbo. They also increase the scavenging effect of the engine.

It is not unusual that there is a limitation in the air flow sensor AFM/MAP on the M155 when loads more air is being sucked into the engine.

You'll see that 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor sapped performance at a much lower level.

Adding a supercharger or additional turbo will make large bhp and torque gains, although more difficult to get working. We have this feature on twinchargers if you want to read more.

Uprating M155 fuel injectors

When you lift the performance you will need to look at to the fuel delivery.

More performance needs more fuel. It makes sense to be generous with your injector capacity.

The accepted safe increase is to add 20% when fitting an injector, which takes into account injector deterioration and affords some 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 M155 performance exhausts

You only need to to boost your exhaust if the current exhaust is actually creating a restriction.

On most factory exhausts you'll find the exhaust flow rate is ok 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 balance the flow of air through the engine.

But if the exhaust pipe is too big, ie: over 2.5 inches bore, you will lose much of the exhaust flow rate and end up sapping power and torque.

Usual exhaust restrictions can be traced to the filters installed, so adding a freer flowing sports alternative will help avoid this restriction.

Problems and issues to look out for on the M155

The M155 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the M155, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your M155 engine please join us in our friendly forum where you can discuss tuning options in more detail with our M155 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 modifications were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our M155 guides and tips are kept up to date.

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This article is flagged for an update, so please pass on specific tips below that I can include. All articles, and content was written by me, Waynne Smith TorqueCars founder. Some outlines are just too general so I appreciate your feedback and suggestions. This entry was filed under Mercedes. You can leave a response below or join our forum to discuss this article and car modification in detail with our members.

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