Tuning the Mercedes M139

"Comprehensive guide to tuning the Mercedes M139 engine!"

We often are getting messages inquiring about getting more power from the M139 and wanting to know what are the premier M139 mods that work. So let us look into Mercedes M139 parts and outline the best modifications on this great engine and point out some frequent tuning mistakes along the way.

The Mercedes M139 are popular tuning projects and with carefully picked sports upgrades like remapping, turbo upgrades and camshafts you will noticeably maximise your driving pleasure.

This pages aim is consider M139 tuning and show the best modifications.

The greatest M139 upgrades on an engine are in our opinion the ones that give the biggest return for your cash.

We won't be swayed by popular M139 upgrades, they need to be cost effective.

Altering your M139 cam will make a dramatic difference to the engine power band. Choosing a higher performance cam profile raises the power band accordingly.

NB: Fast road camshafts normally boost the bhp through the rev band, you may sacrifice a little low end power but the high end rpm power will be higher.

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

A Competition cam will just annoy you whilst driving in heavy traffic.

You should ideally optimize your torque band to your driving style so for a typical daily driver stick with a mild fast road M139 cam

Some M139 engines respond better to extreme cam durations check your engine on a rolling road.

The ecu map and fuelling also will make differences on the bhp gains you'll hit.

Altering valve durations can alter the bhp 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.

M139 Tuning Stages

Stage 1 M139 modifications: Drilled & smoothed airbox, Fast road camshaft, Sports exhaust manifold, Panel air filters, Intake headers, Remaps/piggy back ECU.

Stage 2 M139 modifications: induction kit, Fast road cam, high flow fuel injectors, fuel pump upgrades, Sports catalyst & performance exhaust, Ported and polished head.

Stage 3 M139 modifications: Competition cam, Adding or Upgrading forced induction (turbo/supercharger), Crank and Piston upgrades to alter compression, Internal engine upgrades (head flowing porting/bigger valves), Engine balancing & blueprinting, Twin charging conversions.

Remaps should help to unlock the full potential of all the tuning parts you've done to your M139.

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 differs on the tuning parts you've fitted and the condition of your engine.

It is the whole point to any engine modification task to feed fuel and air into your M139

Intake headers take the air during the suck phase from the filter and allow it to be drawn into the engine cylinders.

The shape and flow characteristics of the Intake headers can make a large effect on to fuel atomisation on the M139.

It's not uncommon that intake are improved through aftermarket tuning parts, although some makers provide fairly well optimized intake.

Adding a M139 larger valve kit, doing some M139 port enlargement and head flowing will also lift bhp, this will give you a better bhp increase on other upgrades.

Turbo upgrades for the M139

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 M139

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 going to make more power and you'll see that turbocharged engines already contain better components.

However you'll find engines will need better parts at higher power limits

See where you'll find these limits and upgrade to better quality components to handle the power.

There are many car owners spending a lot of money on turbo charger upgrades on the M139 only to have the M139 literally blow up soon after it's used on the roads.

Big capacity turbo units commonly experience low end lag, and little turbo units spool up quickly but won't have the high rpm torque gains.

In the last 10 years the world of turbos is always evolving and we commonly find 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 2 channels and feed these at differently designed vanes in the turbo charger. They also help the scavenging effect of the engine.

It is common that there's a restriction in the air flow sensor (AFM/MAF/MAP) on the M139 when loads more air is being fed into the engine.

We see 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor limited bhp at a much lower level.

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

Uprating M139 fuel injectors

You will need to ensure that the engine is not starved of fuel so will need to ramp up the fuelling when you start exceeding 20% of a bhp and torque increase.We would 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 provides you 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 M139 performance exhausts

You only need to to increase your exhaust if the existing exhaust is creating a flow problem.

On most factory exhausts you'll see the exhaust flow rate is still ok even on modest power gains, but when you start pushing up the power levels you will need to get a better flowing exhaust.

Do not go with the widest exhaust you can find you'll slow up the exhaust flow rate - the best for power gains are usually between 1.5 to 2.5 inches. It is the shape and material more than the bore size.

Usual exhaust restrictions can be located the catalysts installed, so adding a better flowing race alternative will help avoid this restriction.

Problems and issues to look out for on the M139

The M139 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the M139, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your M139 engine please join us in our friendly forum where you can discuss tuning options in more detail with our M139 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 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 M139 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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