Modding tuning and best performance upgrades on the Mercedes OM604 engine!

Tuners tips on "OM604 Modifications"

OM604 Modifications Guide

How to modify and upgrade the Mercedes OM604

"Comprehensive guide to performance tuning the Mercedes OM604 engine!"

Forums like the one at TorqueCars often are getting posts requesting info on how to improve the OM604 from people inquiring about getting more power from the OM604 and wanting to know what are the ultimate OM604 modifications. So let us look into Mercedes OM604 upgrades and outline the best modifications on this great engine and point out some frequent tuning mistakes along the way.

The Mercedes OM604 make awesome project engines and with the right performance parts like a remap, turbo upgrades and camshafts you will dramatically enhance your driving opportunities.

In this article we outline options for your OM604 tuning and summarise the ultimate modifications for your car.

Just because particular tuning mods are popular with OM604 owners it doesn't mean it is good, instead we will focus on the top tuning mods that will give your OM604 the best value for money to power increase.

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'.

OM604 induction kits

Improving air intake on the OM604

You need fuel and air for an engine to work. If there is little supply of fuel then it will run lean, if there is too little air it runs rich losing power which risks damage to the OM604. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So Feeding more air into the OM604 engine is vital to any engine tuning project.

It is common that there is a restriction in the air flow sensor (AFM/MAF/MAP) on the OM604 when loads more air is being drawn into the engine.

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

Intake manifolds carry the during the engines suck phase from the filter and allow it to be drawn into the engine cylinders.

The shape and flow rate of the Headers can make a noticeable change to fuel engine efficiency on the OM604.

I usually find intake are improved through motorsport parts, although some OEM provide reasonably good intake.

Adding a OM604 larger valve kit, getting port work and head flowing will also lift power, this will afford you raising the power increase on other tuning parts.

OM604 performance cam tips.

Some OM604 engines respond better to less aggressive camshaft durations so set your engine up on a rolling road.

The engine timing and fuelling also have an effect on the power gains you'll hit.

A longer valve duration 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.

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

NB: Fast road camshafts normally boost the bhp over the rpm range, you could sacrifice a little low end bhp 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 camshaft won't do well if in heavy traffic.

You should ideally match your engines power to your usage of the car so for a car used daily stick with a shorter duration OM604 camshaft

Stage 1, 2 and 3 mods for the OM604

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 OM604 parts:

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

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

Stage 2 OM604 parts:

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

Stage 3 OM604 parts:

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

The OM604 engine blocks respond well to mods and we note that there are increasing numbers of mods and performance parts about.

Remapping allows a tuner to unlock the full potential of all the parts you've done to your OM604.

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

Turbo modifications on the OM604

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 OM604.

The more air you can get into an engine, the more fuel it can burn and uprating the induction with a turbocharger upgrade makes impressive power gains.

If the engine is turbocharged, parts are relatively easy and you'll see that turbo charged engines already contain many forged and stronger components.

However you'll find engines will have power limits

We recommend you find these limits and install more solid crank and pistons to survive the power.

We see many drivers spending a loads on turbo upgrades on the OM604 only to experience the engine block explode soon after it's used in anger.

Bigger turbo chargers tend to suffer a bottom end lag, and smaller turbo chargers spool up much more quickly but won't have the peak end power band gains.

Thanks to new tech the market of turbochargers is always developing and we now see variable vane turbochargers, allowing the vane profile is altered according to speed to lower lag and increase top end bhp and torque.

Twin scroll turbochargers divert the exhaust gases into a couple of channels and push these at differently designed vanes in the turbo charger. 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 bhp gains, although more difficult to get working. We have this feature on twinchargers if you want to read more.

Tips about fuel supply on the OM604

Don't miss you'll need to improve the fuel delivery when you are increasing the bhp and torque - it makes the car more thirsty. Most tuners we speak with say to be generous with your injector capacity.

As a rule of thumb add 15% capacity when buying an injector, this takes into account injector deterioration and affords 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 OM604 performance exhaust upgrades

You should look to increase your exhaust system with an upgraded one is if the existing exhaust is actually creating a restriction in flow.

On most factory exhausts you should find that the exhaust flow rate is still 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.

Sports exhausts increase the flow of air through the engine.

But if the exhaust pipe is too big, ie: over two and a half inches diameter, you will lose a lot of the flow rate and end up losing power and torque.

Usual exhaust restrictions come around the catalysts installed, so adding a faster flowing race alternative will help avoid this restriction.

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

Faults issues and things to look out for on the OM604

Like most engines an OM604, 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 OM604, failure to do this will exacerbate engine wear, on a tuned OM604 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 OM604 why not pop over to the forums at TorqueCars where you can chat about OM604 tuning options and read about others projects who may be planning to do similar modifications on their OM604.

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