Tuning the Mercedes M112

"Comprehensive guide to tuning the Mercedes M112 engine!"

We are always getting emails requesting information on the best tips for M112 upgrades. So let us look into Mercedes M112 tuning mods and outline the best upgrades on this great engine and point out some potential pitfalls along the way.

We shall review M112 tuning and point out the best mods that work. Mercedes M112 are popular tuning projects and with carefully picked uprated modifications like a remap, turbo improvements and camshafts you will positively maximise your driving opportunities.

The ultimate M112 tuning parts on an engine are as we have found the ones that give the biggest return for your cash.

We won't be swayed by popular M112 tuning parts, they need to be cost effective.

Significant gains on the M112 can be made from cam upgrades. Altering the cam profile alters the intake and exhaust durations on the engine and can dramatically change the bhp and power output.

NB: Fast road cams usually push up the torque through the rev range, you could sacrifice a little low end torque but high end rpm power will be lifted.

Race cams, push up 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 in heavy traffic.

You should ideally optimize your engines power to your preferences so for a car used daily stick with a shorter duration M112 cam

Each engine responds better to less aggressive camshaft durations so view each engine as unique.

The ECU mapping and fuelling also have a large bearing on the bhp gains you'll achieve.

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.

M112 Tuning Stages

Stage 1 M112 modifications: Fast road camshaft, Intake headers, Drilled & smoothed airbox, Remaps/piggy back ECU, Panel air filters, Sports exhaust manifold.

Stage 2 M112 modifications: induction kit, Ported and polished head, fuel pump upgrades, Fast road cam, high flow fuel injectors, Sports catalyst & performance exhaust.

Stage 3 M112 modifications: Twin charging conversions, Crank and Piston upgrades to alter compression, Competition cam, Engine balancing & blueprinting, Adding or Upgrading forced induction (turbo/supercharger), Internal engine upgrades (head flowing porting/bigger valves).

Carefully think through your options and then source your parts and set yourself a power target to avoid disappointment.

Mapping will help unlock the full potential of all the upgrades you've done to your M112.

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but figures achieved usually differs on the upgrades you've fitted and the condition of your engine.

Shoving more air into each cylinder is the whole point to any engine tuning project.

Intake manifold flow the air during the suck phase from the air filter and allow it to be sucked into the engine and mixed with fuel.

Shape and rate of flow of the Intake can make a big change to fuel engine efficiency on the M112.

We often see headers are needing an upgrade, although some manufacturers provide well optimised headers.

Big valve conversions on the M112, doing a bit of port matching and head flowing will also lift torque, the fantastic side effect is it will afford you an improved torque increase on other parts.

Turbo upgrades for the M112

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 M112

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 car is fitted with a turbocharger tuning parts are more reliable and turbo charged engines are built with stronger components.

There are reliable limits for every engine, with some being over specified and some only able to handle stock power

Discover these limitations and fit more solid crank and pistons to handle the power.

There are many mechanics spending a lot of money on turbo charger upgrades on the M112 only to suffer the humiliation of seeing the M112 throw a rod when it's been finished.

Bigger upgraded turbo units often suffer a bottom end lag, and low capacity turbo units spool up really quickly but do not have the top end torque gains.

We are pleased that the range of turbos is always developing and we commonly find variable vane turbos, permitting the vane angle is altered according to speed to lower lag and increase top end bhp.

Twin scroll turbos divert the exhaust flow into 2 channels and flow these at differently profiled vanes in the turbo. They also boost the scavenging effect of the engine.

It is common that there is a limit in the air flow sensor AFM/MAF on the M112 when considerably more air is being fed into the engine.

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

Adding a supercharger or additional turbo will make large power gains, although more complex to get working. We have this in depth look at twinchargers if you want to read more.

Uprating M112 fuel injectors

When you increase the bhp you will need to pay attention to to the fuel system.

More bhp needs more fuel. It is important to over specify 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 allows a bit of 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 M112 performance exhausts

You may need to improve your exhaust if your current exhaust is creating a restriction in flow.

On most factory exhausts you should find that the 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.

Do not go with the largest exhaust you can buy this will slow up the exhaust flow rate - the best exhausts for power gains are usually between 1.5 to 2.5 inches. It is the shape and material more than the bore size.

Typically exhaust restrictions are in the emissions filters installed, so adding a faster flowing sports alternative will help avoid this restriction.

Problems and issues to look out for on the M112

The M112 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the M112, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your M112 engine please join us in our friendly forum where you can discuss tuning options in more detail with our M112 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 modifications were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our M112 guides and tips are kept up to date.

PLEASE HELP: I NEED YOUR DONATIONS TO COVER THE COSTS OF RUNNING THIS SITE AND KEEP IT RUNNING. I do not charge you to access this website and it saves most TorqueCars readers $100's each year - but we are NON PROFIT and not even covering our costs. To keep us running PLEASE Donate here

If you liked this page please share it with your friends, drop a link to it in your favourite forum or use the bookmarking options to save it to your social media profile.

Please watch this video on our new YouTube channel.


Please use our forums if you wish to ask a tuning question, and please note we do not sell parts or services, we are just an online magazine.

Help us improve, leave a suggestion or tip

Your Constructive comments on this article

Member Benefits

Join our forum today and benefit from over 300,000 posts on tuning styling and friendly car banter.

You will also have full access to the modifed car gallery, project car updates and exclusive member only areas.

(All car owners of all ages and from all countries are welcome).