Modding and performance tuning parts for the Mercedes OM626 engine!

Tuning guide "OM626 Modifications"

OM626 Modifications Guide

How to modify and upgrade the Mercedes OM626

"Comprehensive guide to tuning the Mercedes OM626 engine!"

Popular tuning sites like TorqueCars are frequently getting messages requesting information on how to improve the OM626 from people wanting to know what are the greatest OM626 power upgrades. So let us look into Mercedes OM626 parts and outline the best modifications on this great engine and point out some frequent tuning mistakes along the way.

The Mercedes OM626 are good project engines and with a few sensible tuning enhancements like remaps, turbo upgrades and camshafts you will greatly enhance your driving opportunities.

In this article we review OM626 tuning and show the ultimate modifications for your car.

Just because particular mods are popular with OM626 owners it doesn't mean its worth having, so we'll concentrate on the top mods that will give your OM626 the biggest power gain return for your cash.

Without us subscribing to the popular myth of 'if it's shiny and makes more noise it must be good' you seem to get in many tuning magazines and on car forums'.

OM626 induction kits

Improving air intake on the OM626

You need air matched to fuel for an engine to work. If there is a lack of fuel then it will run lean, if there is too little air it runs rich resulting in lost power which risks damage to the OM626. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So Pushing air and fuel into each cylinder is the primary aim to any engine tuning job.

You'll commonly see there's a limitation in the air flow sensor MAF/MAP on the OM626 when considerably more air is being fed into the engine.

When tuning you may well find you need to get an air sensor or flow meter capable of upto 4 bars to cope with quite large power gains, whereas the OEM air sensor limited performance at a much lower level.

The intake plenum transmit the during the engines suck phase from the filter and allow it to be sucked into the engine cylinders.

The bore size, shape and rate of flow of the Intake headers can make a substantial change to fuel delivery on the OM626.

We often see air intake manifolds are in dire need of aftermarket parts, although some manufacturers provide decently flowing air intake manifolds.

Increasing the OM626 valve size, doing some 3 or 5 angle valve jobs and porting and head flowing will also raise bhp, this will make space for increasing the bhp increase on other tuning parts.

OM626 performance cam tips.

Each engine responds better to more aggressive camshaft durations check your engine on a rolling road.

The engine timing and fuelling also have a large bearing on the torque gains you'll get.

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.

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 normally raise the performance through the rpm band, you may lose a little low down torque but your 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.

On a car driven daily you must carefully try to optimize your engines power to your usage of the car.

I'd be shocked if you have found a OM626 Competition cam is a pleasure to live with when driving in heavy traffic.

Stage 1, 2 and 3 mods for the OM626

Before we break the best tuning upgrades down into stages of tune, let's list the most effective tuning upgrades for you.

  1. Suspension Upgrades - always improve your cars handling
  2. Brake Upgrades - Even before adding power improve those brakes
  3. Intake - make sure the intake is not restricted, use filters and intake upgrades to improve this
  4. Exhaust - as with 3 ensure there is not restriction in the exhaust, cats are the usual bottleneck
  5. Tunes - remapping, piggyback ECU's and aftermarket ECU's can all make decent gains
  6. Fuelling - when you've increased power you'll need to match this with more fuel
  7. Turbo upgrades - Improving the intake with a large turbo and better flowing intercooler will be the biggest power gain you'll see (but one of the most complex).

This video guide to tuning cars is a great starting point to work from in your project.

Stage 1 OM626 parts:

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

Stage 2 OM626 parts:

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

Tuning tips and articles Engine tuning Transmission tuning Care care Intake & exhaust mods Improve handling Forums

Stage 3 OM626 parts:

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

Carefully think through your options and then find your parts and set yourself a power target to avoid expensive mistakes.

Mapping should help to release the full potential of all the upgrades you've done to your OM626.

You will typically expect to see gains of approximately 20-30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but power output may depend much on the upgrades you've done and the condition of your engine.

Turbo modifications on the OM626

To get a turbo working on a NASP engine there is a lot involved, from lowering compression ratio to improved fuel supply and mapping, so we have found a great guide to helpavoid the common pitfalls or end up with an unfinished project because you were not told what you were getting into by doing this on the OM626.

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.

When the engine is fitted with a turbocharger upgrades are going to net you a larger power gain and you will discover turbo charged engines are built with harder and stronger components.

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

Discover these limits and upgrade to better pistons and crank to cope with the power.

There are many guys spending a lots of money on turbo upgrades on the OM626 only to watch the engine block throw a rod on it's first outing after it's finished.

Larger turbo chargers often experience low end lag, and smaller turbo chargers spool up really quickly but won't have the peak end bhp gains.

In recent times the selection of turbo chargers is always moving on and we are seeing variable vane turbo chargers, where the vane angle is altered according to speed to lower lag and increase top end performance.

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

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large performance gains, although more difficult to configure. We have this guide to twinchargers if you want to read more.

Tips about fuel supply on the OM626

You will need to ensure that the engine is not starved of fuel so need to look at the fuelling when you start extending past 20% of a power hike. It makes sense to over specify your injectors flow rate.

The rule of thumb is to add 15% when specifying an injector, this accounts for injector deterioration and gives a little spare capacity should the engine require more fuel.

Don't forget that different fuel grades will usually require different settings, a high octane fuel will burn more efficiently than lower octane fuel for example. A car will trim fuel supply to keep within the ideal air fuel mix but at the extreme ends you may need to adjust your injector capacity, or the mapping or you'll get flat spots and potential lean or rich fuel issues..

Recommended OM626 performance exhaust upgrades

The only time you should look to upgrade your exhaust system with an upgraded one is if your current exhaust is actually causing a flow problem.

On most factory exhausts you should find that the flow rate is good even on modest power gains, but on a serious tuning project with a big boost in power you will certainly need to get a better flowing exhaust.

Note that with the biggest exhaust you can get this will slow the exhaust rate - the best for power gains are usually between one and a half to two and half inches. Your exhaust design, the bend angles and construction are what have more effect on flow rates than your pipe width to a certain extent. So the exhaust design is a big factor.

Usual exhaust restrictions are in the catalyst and filters installed, so adding a faster flowing race alternative will help avoid this restriction.

Catalyst removal (NB:catalysts reduce harmful engine emissions) is illegal in most countries and regions.

Faults issues and things to look out for on the OM626

Like most engines an OM626, should have few issues if it gets properly serviced and looked after.

We cannot stress enough the need for oil changes with the correct grade of oil on the OM626, failure to do this will exacerbate engine wear, on a tuned OM626 this is more important than ever and close attention should be paid to your maintenance schedule.

If you are interested in learning more or getting impartial tuning advice for your OM626 why not pop over to the forums at TorqueCars where you can chat about OM626 tuning options and read about others projects who may be planning to do similar modifications on their OM626.

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