Tuning the Mercedes OM604

"Comprehensive guide to tuning the Mercedes OM604 engine!"

We are regularly getting messages about the best tips for OM604 modifications. So let us look into Mercedes OM604 modifications and outline the best modifications on this great engine and point out some frequent tuning mistakes along the way.

The Mercedes OM604 are popular engines and with the right performance modifications like a remap, turbo kits and camshafts you will certainly maximise your driving fun.

In this article we look into OM604 tuning and show the best modifications for your car.

Just because particular tuning mods are appear in lots of OM604 projects it doesn't mean it is good, we will focus tuning mods that will give your OM604 the biggest power gain return for your cash.

Significant gains on the OM604 can be made from cam upgrades. Altering the cam profile alters the intake and exhaust durations on the engine and can dramatically change the torque and power output.

NB: Fast road cams tend to boost the bhp through the rpm band, you may sacrifice a little bottom end bhp but top end will improve.

Motorsport cams, boost the top end band but as a result the car will not idle smoothly and low end power nearly always suffers.

For a car used daily must carefully try to optimize your bhp range to your driving style.

I'd be gobsmaked if you have ever thought a OM604 Motorsport and race cam is a pleasure to live with when in heavy traffic.

Different OM604 engines respond better to mild camshaft durations than others.

The engine timing and fuel pump and injectors also have a large bearing on the torque gains you'll make.

A longer valve duration 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.

OM604 Tuning Stages

Stage 1 OM604 modifications: Fast road camshaft, Intake headers, Sports exhaust manifold, Remaps/piggy back ECU, Panel air filters, Drilled & smoothed airbox.

Stage 2 OM604 modifications: Ported and polished head, induction kit, Sports catalyst & performance exhaust, fuel pump upgrades, high flow fuel injectors, Fast road cam.

Stage 3 OM604 modifications: Adding or Upgrading forced induction (turbo/supercharger), Internal engine upgrades (head flowing porting/bigger valves), Crank and Piston upgrades to alter compression, Twin charging conversions, Competition cam, Engine balancing & blueprinting.

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

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

It is the whole point to any tuning project to force more fuel and air into each cylinder

Headers transmit the air from the filter and allow it to be pulled into the engine and mixed with fuel.

The size of bore and shape and rate of flow of the Intake headers can make a big difference to to fuel engine efficiency on the OM604.

Many mass produced engine intake are in dire need of performance upgrades, although some OEM provide decently flowing intake.

Larger OM604 valves, carrying out port matching and head flowing will also boost bhp and torque, and importantly will give you an improved bhp and torque increase on other tuning parts.

Turbo upgrades for the OM604

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 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 major power gains.

If the engine has a turbocharger parts are simpler to install and turbo charged engines already contain strengthened components.

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

It is important to find these limitations and install better quality crank and pistons to handle the power.

There are many guys spending a fortune on turbo upgrades on the OM604 only to suffer the humiliation of seeing the motor throw a rod soon after it's used on the roads.

Large capacity turbo chargers often experience no power at low rpm, and low capacity turbo chargers spool up much more quickly but don't have the top end bhp gains.

In recent times the selection of turbochargers is always increasing and we now see variable vane turbochargers, where the vane angle is altered according to speed to lower lag and increase top end performance.

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

You'll commonly see there's a restriction in the air flow sensor MAF/MAP on the OM604 when loads more air is being pulled into the engine.

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

Adding a supercharger or additional turbo will make large bhp and torque gains, although more challenging to install. We have this feature on twinchargers if you want to read more.

Uprating OM604 fuel injectors

Don't omit to increase the fuelling when you are increasing the power - it makes the car more thirsty. We strongly recommend you to over specify your injector capacity.

The rule of thumb is to add 20% to the flow rate when buying an injector, this allows for injector deterioration and provides you some 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 OM604 performance exhausts

Only look to improve your exhaust if the current exhaust is creating a restriction.

On most factory exhausts you should find that 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.

Do not go with the widest exhaust you can find 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.

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

Problems and issues to look out for on the OM604

The OM604 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the OM604, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your OM604 engine please join us in our friendly forum where you can discuss tuning options in more detail with our OM604 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 OM604 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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