Tuning the Mercedes M157

"Comprehensive guide to tuning the Mercedes M157 engine!"

We are always seeing threads asking how to improve the M157 from people wanting to know what are the greatest M157 power upgrades. So let us look into Mercedes M157 upgrades and outline the best modifications on this great engine and point out some frequent tuning mistakes along the way.

In this article we review M157 tuning and outline the optimum upgrades. Mercedes M157 are fantastic to work on and with the optimum parts like remapping, turbo improvements and camshafts you will definitely improve your driving opportunities.

The best M157 modifications on an engine are as we have found the ones that give the best power gain for you spend.

We won't be swayed by popular M157 modifications, they need to be cost effective.

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

NB: Fast road cams commonly bump the bhp and torque across the rev range, you could sacrifice a little low down bhp but your higher rpm power will be lifted.

Motorsport and race cams, bump the higher rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

In a car used daily you need to optimize your torque band to your usage of the car.

I'd be gobsmaked if you have ever thought a M157 Motorsport camshaft is a pleasure to live with when on the daily commute.

Different M157 engines respond better to more aggressive cam durations so view each engine as unique.

The map and fuel pump and injectors also have a large bearing on the power gains you'll achieve.

Longer 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.

M157 Tuning Stages

Stage 1 M157 modifications: Intake headers, Drilled & smoothed airbox, Remaps/piggy back ECU, Panel air filters, Fast road camshaft, Sports exhaust manifold.

Stage 2 M157 modifications: fuel pump upgrades, Sports catalyst & performance exhaust, induction kit, Fast road cam, high flow fuel injectors, Ported and polished head.

Stage 3 M157 modifications: Adding or Upgrading forced induction (turbo/supercharger), Engine balancing & blueprinting, Competition cam, Internal engine upgrades (head flowing porting/bigger valves), Twin charging conversions, Crank and Piston upgrades to alter compression.

ECU flashing will help to establish the full potential of all the parts you've done to your M157.

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

It is the main goal to any tuning task to get air into the M157 engine

The intake plenum transmit the air during the suck phase from the intake filter and allow it to be fed into the engine and mixed with fuel.

The shape and flow rate of the Intake can make a large change to fuel mixing and power on the M157.

We often see headers are crying out for aftermarket parts, although some OEM provide well optimised headers.

Larger M157 valves, carrying out port matching and head flowing will also improve torque, & importantly will permit raising the torque increase on other upgrades.

Turbo upgrades for the M157

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 M157

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.

When your car is turbo charged tuning mods are more reliable and we find turbo engines are made using harder and stronger components.

There are common areas of failure for every engine, with some being incredibly solid and some just sufficiently able to handle stock power

Research these restrictions and install higher quality components to utilize the power.

We see many car owners spending a lots of money on turbo upgrades on the M157 only to have the engine go up in smoke on it's first outing after it's been finished.

Large upgraded turbos tend to suffer low end lag, and low capacity turbos spool up really quickly but don't have the peak end bhp gains.

In recent times the market of turbochargers is always improving and we are seeing 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 two channels and flow these at differently profiled vanes in the turbo charger. They also improve the scavenging effect of the engine.

You'll commonly see there's a limitation in the air flow sensor AFM/MAF on the M157 when loads more air is being sucked into the engine.

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

Adding a supercharger or additional turbo will make large performance gains, although more difficult to setup. We have this in depth look at twinchargers if you want to read more.

Uprating M157 fuel injectors

Don't overlook the need to look at the fuel system when you are increasing the bhp and torque - it makes the car more thirsty. Most tuners we speak with say to over specify your injectors flow rate.

As a rule of thumb add 20% when specifying an injector, helps cope with injector deterioration and provides a bit of 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 M157 performance exhausts

Only look to upgrade your exhaust if your exhaust is actually creating a restriction.

On most factory exhausts you'll find the exhaust 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 generally help improve air flow through the engine but avoid an exhaust that is too big or you may end up will reduce the flow rate. Stick to 1.5 to 2.5 inches as a rule of thumb.

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

Problems and issues to look out for on the M157

The M157 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the M157, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your M157 engine please join us in our friendly forum where you can discuss tuning options in more detail with our M157 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 tuning mods were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our M157 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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