Tuning the Mercedes M178

"Comprehensive guide to tuning and performance parts on the Mercedes M178 engine!"

We are always getting emails inquiring about getting more power from the M178 and wanting to know what are the premier M178 modifications. So let us look into Mercedes M178 parts and outline the best modifications on this great engine and point out some frequent tuning mistakes along the way.

Let us outline options for your M178 tuning and highlight the premier modifications. Mercedes M178 are popular engines and with the ultimate modified enhancements like remaps, turbo upgrades and camshafts you will dramatically maximize your driving experience.

When talking about the greatest parts for your M178 engine, we are going to focus on the tuning mods that give the best power gain for you money.

Significant gains on the M178 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 commonly push up the torque across the rpm band, you might lose a little bottom end torque but your higher rpm power will be higher.

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

A Motorsport cam will just annoy you whilst in heavy traffic.

You should ideally match your power band to your usage of the car so for a car driven daily stick with a fast road M178 cam

Each engine responds better to different cam durations than others.

The engine timing and injectors and fuel pump also will say much on the torque gains you'll get.

A longer valve duration 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.

M178 Tuning Stages

Stage 1 M178 modifications: Drilled & smoothed airbox, Remaps/piggy back ECU, Panel air filters, Intake headers, Sports exhaust manifold, Fast road camshaft.

Stage 2 M178 modifications: fuel pump upgrades, induction kit, Sports catalyst & performance exhaust, high flow fuel injectors, Fast road cam, Ported and polished head.

Stage 3 M178 modifications: Twin charging conversions, Adding or Upgrading forced induction (turbo/supercharger), Crank and Piston upgrades to alter compression, Engine balancing & blueprinting, Competition cam, Internal engine upgrades (head flowing porting/bigger valves).

Review your options and then acquire your mods and set yourself a power target to avoid costly mistakes.

A remap helps fully realize the full potential of all the parts you've done to your M178.

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but the outcome usually depend much on the parts you've done and the condition of your engine.

Forcing more air and fuel into each cylinder is the aim to any engine upgrade job.

Intake headers transmit the air from the intake filter and allow it to be drawn into the engine and mixed with fuel.

Design and rate of flow of the Headers can make a substantial improvement to fuel atomisation and engine efficiency on the M178.

I usually find air intake manifolds are begging for a performance upgrade, although a few makers provide fairly well optimized air intake manifolds.

Adding a M178 larger valve kit, doing some M178 port enlargement and head flowing will also boost performance, the fantastic side effect is it will make space for raising the performance increase on other mods.

Turbo upgrades for the M178

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 M178

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 motor has a turbo already fitted modifications are giving better power gains and we find turbo engines are made using strengthened components.

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

Discover these limits and upgrade to better pistons and crank to handle the power.

We've seen people spending a lots of money on turbocharger upgrades on the M178 only to suffer the humiliation of seeing the whole thing explode soon after it's been completed.

Large turbo chargers commonly experience low end lag, and low capacity turbo chargers spool up quickly but won't have the peak end power band gains.

Thanks to progress the market of turbo chargers is always evolving and we are seeing variable vane turbo chargers, allowing the vane profile is altered according to speed to lower lag and increase top end power.

Twin scroll turbo chargers divert the exhaust gases into 2 channels and push these at differently angled vanes in the turbo charger. They also improve the scavenging effect of the engine.

You'll commonly see there is a limitation in the air flow sensor (AFM/MAF/MAP) on the M178 when considerably 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 limited performance at a much lower level.

Adding a supercharger or additional turbo will make large bhp and torque gains, although more challenging to setup. We have this in depth look at twinchargers if you want to read more.

Uprating M178 fuel injectors

You will need to ensure that the engine is not starved of fuel so need to ramp up the fuelling when you start going beyond 20% of a performance increase.We strongly recommend you to be generous with your flow rate on the injectors.

As a rule of thumb add 20% capacity when specifying an injector, this takes into account injector deterioration and gives a bit of 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 M178 performance exhausts

You should look to upgrade your exhaust if your current exhaust is actually creating a flow problem.

On most factory exhausts you should find that the exhaust flow rate is still fine 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 your exhaust pipe is too large, ie: it's over 2.5 inches bore, you will lose a lot of the exhaust flow rate and end up sapping power and torque.

Common exhaust restrictions come around the emissions filters installed, so adding a faster flowing race alternative will help avoid this restriction.

Problems and issues to look out for on the M178

The M178 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the M178, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your M178 engine please join us in our friendly forum where you can discuss tuning options in more detail with our M178 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 upgrades were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our M178 guides and tips are kept up to date.

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