Tuning the Mercedes M158

"Comprehensive guide to tuning the Mercedes M158 engine!"

We often are getting posts asking how to improve the M158 from people wanting to know what are the things we are recommending when it comes to M158 power upgrades. So let us look into Mercedes M158 upgrades and outline the best upgrades on this great engine and point out some frequent tuning mistakes along the way.

In this article we review and look at M158 tuning and highlight the ultimate modifications for your car. Mercedes M158 are fantastic to work on and with carefully chosen modified modifications like a remap, turbo upgrades and camshafts you will substantially improve your driving opportunities.

When talking about the top parts for your M158 engine, we are going to concentrate on the parts that give the best power gain for you money.

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

NB: Fast road cams tend to raise the bhp through the rpm band, you may sacrifice a little bottom end bhp but higher rpm power will improve.

Race cams, raise the higher 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 is not great driving in heavy traffic.

You should ideally match your engines power to your driving style so for a car used daily stick with a mild fast road M158 camshaft

Each engine responds better to different cam durations so view each engine as unique.

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

Extending exhaust or intake 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.

M158 Tuning Stages

Stage 1 M158 modifications: Drilled & smoothed airbox, Fast road camshaft, Sports exhaust manifold, Panel air filters, Intake headers, Remaps/piggy back ECU.

Stage 2 M158 modifications: Sports catalyst & performance exhaust, fuel pump upgrades, high flow fuel injectors, Fast road cam, induction kit, Ported and polished head.

Stage 3 M158 modifications: Competition cam, Twin charging conversions, Internal engine upgrades (head flowing porting/bigger valves), Engine balancing & blueprinting, Adding or Upgrading forced induction (turbo/supercharger), Crank and Piston upgrades to alter compression.

A remap helps release the full potential of all the tuning parts you've done to your M158.

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

Feeding more air and fuel into your M158 is vital to any engine tuning job.

Air Intake manifolds transmit the air during the suck phase from the intake filter and allow it to be sucked into the engine cylinders with fuel for the squish phase.

The shape and rate of flow of the Intake headers can make a substantial difference to to fuel engine efficiency on the M158.

It's not uncommon that headers are improved through a performance upgrade, although a few manufacturers provide decently flowing headers.

Big valve conversions on the M158, getting port work and head flowing will also raise bhp and torque, and more importantly will give you increasing the bhp and torque increase on other parts.

Turbo upgrades for the M158

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 M158

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.

If your motor has a turbo already fitted upgrades are simpler to install and most turbo charged engines use more solid components.

There are weak spots for every engine, with some being very over engineered and some only able to handle stock power

We recommend you find these restrictions and fit forged components to handle the power.

There are many people spending a a stack of money on turbo charger upgrades on the M158 only to experience the whole thing catastrophically fail on it's first outing after it's been completed.

Large capacity turbochargers often suffer low end lag, and low capacity turbochargers spool up more quickly but don't have the top end engines power gains.

We are pleased that the market of turbos is always developing and we are seeing variable vane turbos, permitting the vane angle is altered according to speed to lower lag and increase top end power.

Twin scroll turbos divert the exhaust gases into a couple of channels and feed these at differently angled vanes in the turbo. They also help the scavenging effect of the engine.

You'll commonly see there's a limitation in the air flow sensor (AFM/MAF/MAP) on the M158 when a lot more air is being fed into the engine.

Going up you'll find 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor was restricting bhp at a much lower level.

Adding a supercharger or additional turbo will make large power gains, although more complex to setup. We have this article on twincharging if you want to read more.

Uprating M158 fuel injectors

When you improve the torque you will need to ramp up to the fuelling.

More torque needs more fuel. Most tuners we speak with say to be generous with your flow rate on the injectors.

As a rule of thumb add 20% capacity when buying an injector, this allows for injector deterioration and provides you 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 M158 performance exhausts

You only need to to replace your exhaust if your exhaust is creating a restriction.

On most factory exhausts you'll see the flow rate is still 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 generally help improve air flow out of the engine but do not go too wide or you could will reduce the flow rate. Stick to 1.5 to 2.5 inches for best results.

Common exhaust restrictions can be located the catalysts installed, so adding a freer flowing performance alternative will help avoid this restriction.

Problems and issues to look out for on the M158

The M158 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the M158, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your M158 engine please join us in our friendly forum where you can discuss tuning options in more detail with our M158 owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

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We really like hearing from our readers, and hearing about which tuning parts were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our M158 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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