Tuning the Mercedes OM642

"Comprehensive guide to tuning the Mercedes OM642 engine!"

We are frequently getting emails about the optimum OM642 power upgrades. So let us look into Mercedes OM642 parts and outline the best modifications on this great engine and point out some common pitfalls along the way.

The Mercedes OM642 make awesome project engines and with carefully chosen motorsport upgrades like a remap, turbo kits and camshafts you will really improve your driving opportunities.

We shall outline options for your OM642 tuning and show the best modifications for your car.

The greatest OM642 tuning mods on an engine are sensibly the ones that give the best power gain for you spend.

We won't be swayed by popular OM642 tuning mods, 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 bhp gains are on offer for camshaft upgrades.

NB: Fast road camshafts normally boost the power over the rev range, you may sacrifice a little low down power but higher rpm power will be higher.

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

For a car driven daily you need to match your torque band to your preferences.

I'd be gobsmaked if you have ever thought a OM642 Competition cam is a pleasure to live with when driving around busy urban areas.

Each engine responds better to extreme cam durations so set your engine up on a rolling road.

The engine timing and injectors and fuel pump also have an effect on the bhp gains you'll hit.

Extending exhaust or intake 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.

OM642 Tuning Stages

Stage 1 OM642 modifications: Remaps/piggy back ECU, Panel air filters, Fast road camshaft, Intake headers, Drilled & smoothed airbox, Sports exhaust manifold.

Stage 2 OM642 modifications: induction kit, fuel pump upgrades, Fast road cam, Ported and polished head, high flow fuel injectors, Sports catalyst & performance exhaust.

Stage 3 OM642 modifications: 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), Twin charging conversions.

The OM642 engines are fantastic to work on and we're pleased to see that there are increasing numbers of modifications and performance parts about.

ECU flashing will help to establish the full potential of all the upgrades you've done to your OM642.

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

Pulling air into each cylinder is the main goal to any engine upgrade project.

Headers carry the air from the filter and allow it to be pulled into the engine cylinders with fuel for the squish phase.

The shape and flow rate of the Headers can make a noticeable effect on to fuel atomisation on the OM642.

Most plenum chambers are ripe for an upgrade, although some car makers provide decently flowing plenum chambers.

Big valve conversions on the OM642, doing some port work and head flowing will also raise bhp and torque, and significantly will permit an improved bhp and torque increase on other parts.

Turbo upgrades for the OM642

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 OM642

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 car has a turbocharger modifications are going to make more power and turbocharged engines are built using strengthened components.

There are practical limits for every engine, with some being extremely strong and some only just able to handle stock power

Discover these limits and upgrade to forged components to handle the power.

We've seen people spending a a stack of money on turbo charger upgrades on the OM642 only to suffer the indignity of watching the engine literally blow up when it's been enthusiastically driven.

Large turbo units often suffer a bottom end lag, and little turbo units spool up really quickly but do not have the high rpm bhp gains.

In the last 10 years the world of turbo units is always developing and we are seeing variable vane turbo units, permitting the vane angle is altered according to speed to lower lag and increase top end bhp and torque.

Twin scroll turbo units divert the exhaust flow into two channels and direct these at differently angled vanes in the turbocharger. They also increase the scavenging effect of the engine.

It is not unusual that there is a limit in the air flow sensor MAP/MAF/AFM on the OM642 when loads more air is being drawn into the engine.

You'll see that 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor sapped performance at a much lower level.

Adding a supercharger or additional turbo will make large torque gains, although more complex to configure. We have this article covering twinchargers if you want to read more.

Uprating OM642 fuel injectors

You will need to ensure that the engine is not starved of fuel so need to ramp up the fuelling when you start exceeding 20% of a bhp increase.We would recommend you to over specify your flow rate on the injectors.

The accepted safe increase is to add another 20% when fitting an injector, this allows for injector deterioration and provides 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 OM642 performance exhausts

You may need to upgrade your exhaust if the existing exhaust is actually causing a restriction.

On most factory exhausts you'll find 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.

Note that with the biggest exhaust you can find this will slow the exhaust 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.

Common exhaust restrictions can be traced to the catalyst and filters installed, so adding a higher flowing sports alternative will help avoid this restriction.

Problems and issues to look out for on the OM642

The OM642 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the OM642, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your OM642 engine please join us in our friendly forum where you can discuss tuning options in more detail with our OM642 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 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 OM642 guides and tips are kept up to date.

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