Tuning the Mercedes M166

"Comprehensive guide to performance tuning the Mercedes M166 engine!"

We are regularly getting emails about the best tips for M166 power upgrades. So let us look into Mercedes M166 parts and outline the best modifications on this great engine and point out some potential pitfalls along the way.

Let us review and look at M166 tuning and show the ultimate mods that work. Mercedes M166 make a good tuning project and with a few sensible performance mods like remapping, turbo kits and camshafts you will certainly increase your driving experience.

Just because particular upgrades are appear in lots of M166 projects it doesn't mean you should fit it, instead we will highlight only those upgrades that we reckon are the best and that will give your M166 the biggest power gain return for your cash.

Significant gains on the M166 can be made from camshaft upgrades. Altering 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 normally bump the torque through the rpm band, you may lose a little low down torque but your higher rpm power will be higher.

Race camshafts, bump 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 makes it harder when driving in heavy traffic.

You should ideally optimize your engines power to your preferences so for a typical daily driver stick with a fast road M166 camshaft

Each engine responds better to more or less aggressive camshaft durations check your engine on a rolling road.

The ecu map and fuel pump and injectors also will make differences on the torque gains you'll hit.

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.

M166 Tuning Stages

Stage 1 M166 modifications: Drilled & smoothed airbox, Fast road camshaft, Remaps/piggy back ECU, Intake headers, Panel air filters, Sports exhaust manifold.

Stage 2 M166 modifications: Fast road cam, fuel pump upgrades, Sports catalyst & performance exhaust, induction kit, high flow fuel injectors, Ported and polished head.

Stage 3 M166 modifications: Crank and Piston upgrades to alter compression, Twin charging conversions, Internal engine upgrades (head flowing porting/bigger valves), Competition cam, Adding or Upgrading forced induction (turbo/supercharger), Engine balancing & blueprinting.

Carefully think through your options and then acquire your modifications and set yourself a power target to avoid wasting your time and money.

Remaps will help unlock the full potential of all the tuning mods you've done to your M166.

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 often rely on the tuning mods you've applied and the condition of your engine.

It is the main goal to any engine tuning job to push air and fuel into each cylinder

Intake headers transmit the air from the air cleaner and allow it to be sucked into the engine cylinders with fuel for the squish phase.

Structure and flow rate of the Headers can make a big change to fuel atomisation on the M166.

On popular production engines air intake manifolds are needing performance upgrades, although a few manufacturers provide reasonably well designed air intake manifolds.

Big valve conversions on the M166, carrying out M166 port enlargement and head flowing will also improve performance, & more importantly will allow you to get a greater performance increase on other parts.

Turbo upgrades for the M166

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 M166

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

If your motor has a turbocharger upgrades are more reliable and turbocharged engines are built using more solid components.

However you'll find engines have limits

We recommend you find these limits and fit better quality components to survive the power.

We've seen people spending a loads on turbocharger upgrades on the M166 only to have the whole thing throw a rod on it's first outing after it's finished.

Larger upgraded turbos often suffer low end lag, and small turbos spool up much more quickly but do not have the high rpm engines power gains.

Thanks to new tech the world of turbos is always increasing and we now see variable vane turbos, where the vane profile is altered according to speed to lower lag and increase top end torque.

Twin scroll turbos divert the exhaust gases into a couple of channels and push these at differently designed vanes in the turbocharger. They also increase the scavenging effect of the engine.

It is not unusual that there's a limit in the air flow sensor MAP/MAF/AFM on the M166 when considerably more air is being fed 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 complex to install. We have this feature on twinchargers if you want to read more.

Uprating M166 fuel injectors

You will need to ensure that the engine is not starved of fuel so will have to look at the fuelling when you start extending past 20% of a performance increase.Most tuners we speak with say to be generous with your flow rate on the injectors.

As a rule of thumb add 20% when specifying an injector, which takes into account injector deterioration and allows some spare capacity should the engine require 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 M166 performance exhausts

You may need to increase your exhaust if your exhaust is actually creating a flow problem.

On most factory exhausts you should find that the flow rate is good 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 can usually air flow from the engine but do not go too large or you could will reduce the flow rate. Stick to 1.5 to 2.5 inches for best results.

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

Problems and issues to look out for on the M166

The M166 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the M166, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your M166 engine please join us in our friendly forum where you can discuss tuning options in more detail with our M166 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 M166 guides and tips are kept up to date.

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