Everything You Need To Know About "M166 Modifications"

How to modify and upgrade the Mercedes M166

"Comprehensive guide to tuning the Mercedes M166 engine!"

Forums like the one at TorqueCars are regularly getting posts about how to improve the M166 from people inquiring about getting more power from the M166 and wanting to know what are the greatest M166 mods that work. So let us look into Mercedes M166 parts and outline the best upgrades on this great engine and point out some frequent tuning mistakes along the way.

Here we examine M166 tuning and show the greatest modifications. Mercedes M166 make a good tuning project and with the right motorsport upgrades like remapping, turbo improvements and camshafts you will certainly increase your driving opportunities.

The optimum M166 parts on an engine are typically the ones that give the biggest return for your money.

We won't be swayed by popular M166 parts, they need to be cost effective.

Improving air intake on the M166

You need air matched to 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 sapping power which risks damage to the M166. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So the fundamental goal to any car tuning job to feed air into each cylinder but this has a knock on effect with the air flow sensor.

You'll commonly see there's a limitation in the air flow sensor MAP/MAF/AFM on the M166 when loads more air is being drawn 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 at a much lower level.

Intake take the on the suck phase from the air cleaner and allow it to be pulled into the engine cylinders.

Shape and flow rate of the Intake headers can make a noticeable improvement to fuel delivery on the M166.

On popular production engines plenum chambers are in dire need of motorsport parts, although a few car makers provide well optimised plenum chambers.

Larger M166 valves, doing a bit of 3 or 5 angle valve jobs and porting and head flowing will also raise torque, and as an added benefit will permit a greater torque increase on other upgrades.

M166 performance cam tips.

Different M166 engines respond better to more aggressive camshaft durations check your engine on a rolling road.

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

Altering 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.

Significant air intake, and exhaust improvements on the M166 can be made from cam upgrades. Changing the cam profile alters the intake and exhaust durations on the engine and can dramatically change the bhp and power output.

NB: Fast road camshafts tend to push up the performance across the rpm range, you might lose a little low down power but your higher rpm power will be better.

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 Competition cam won't do well if driving around busy urban areas.

You should ideally optimize your power band to your usage of the car so for a typical daily driver stick with a shorter duration M166 cam

Stage 1, 2 and 3 mods for the M166

Before we break the best tuning upgrades down into stages of tune, let's list the most effective tuning upgrades for you.

1. Suspension Upgrades - always improve your cars handling
2. Brake Upgrades - Even before adding power improve those brakes
3. Intake - make sure the intake is not restricted, use filters and intake upgrades to improve this
4. Exhaust - as with 3 ensure there is not restriction in the exhaust, cats are the usual bottleneck
5. Tunes - remapping, piggyback ECU's and aftermarket ECU's can all make decent gains
6. Fuelling - when you've increased power you'll need to match this with more fuel
7. Turbo upgrades - Improving the intake with a large turbo and better flowing intercooler will be the biggest power gain you'll see (but one of the most complex).

This video guide to tuning cars is a great starting point to work from in your project.

Stage 1 M166 parts:

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

Stage 2 M166 parts:

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

Stage 3 M166 parts:

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

A remap will help unlock the full potential of all the tuning parts you've done to your M166.

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 power output usually differs on the tuning parts you've carried out and the condition of your engine.

Turbo modifications on the M166

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 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 excellent power gains.

If an engine is fitted with a turbo upgrades are giving better power gains and turbo engines are built with more solid components.

However most engines will have power limits

It is important to find these limits and fit stronger pistons, crank and engine components to utilize the power.

We've seen people spending a loads of money on turbo upgrades on the M166 only to watch the whole thing catastrophically fail soon after it's been finished.

Big capacity turbo chargers often experience low end lag, and low capacity turbo chargers spool up much more quickly but don't have the peak end bhp gains.

Thanks to new tech the market of turbochargers is always developing and we commonly find variable vane turbochargers, where the vane angle is altered according to speed to lower lag and increase top end bhp and torque.

Twin scroll turbochargers divert the exhaust flow into a couple of channels and feed these at differently angled vanes in the turbo charger. They also improve the scavenging effect of the engine.

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

Tips about fuel supply on the M166

Don't dismiss the need look at the fuel system when you are increasing the performance - it makes the car more thirsty. We strongly recommend you to be generous with your flow rate on the injectors.

As a rule of thumb add 15% capacity when buying an injector, this allows for injector deterioration and gives a little 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 M166 performance exhaust upgrades

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

On most factory exhausts you'll find your flow rate is good 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.

Don't go with the biggest exhaust you can buy you'll slow up the exhaust flow rate - the best for power gains are usually between one and a half to two and half inches. Your exhaust design, the bend angles and construction are what have more effect on flow rates than your pipe width to a certain extent. So the exhaust design is a big factor.

The usual suspects causing problems in your exhaust flow rate can be traced to the catalyst and filters installed, so adding a faster flowing high performance alternative will help avoid this restriction.

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

Faults issues and things to look out for on the M166

Like most engines an M166, 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 M166, failure to do this will exacerbate engine wear, on a tuned M166 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 M166 why not pop over to the forums at TorqueCars where you can chat about M166 tuning options and read about others projects who may be planning to do similar modifications on their M166.

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This entry was posted under Makes and Models. Tags: engine, mercedes
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