Tuners tips on "OM668 Modifications"

OM668 Modifications Guide

How to modify and upgrade the Mercedes OM668

"Comprehensive guide to tuning the Mercedes OM668 engine!"

Forums like the one at TorqueCars are always getting emails requesting information on how to improve the OM668 from people wanting to know what are the best tips on OM668 power upgrades. So let us look into Mercedes OM668 mods and outline the best mods that work on this great engine and point out some potential pitfalls along the way.

The Mercedes OM668 really good project engines and with carefully picked motorsport parts like remaps, turbo upgrades and camshafts you will really enhance your driving pleasure.

We shall provide a guide to OM668 tuning and outline the ultimate modifications for your car.

When talking about the greatest parts for your OM668 engine, we are going to concentrate on the parts that give the best power gain for you spend.

Improving air intake on the OM668

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

So the primary aim to any engine upgrade job to feed more air and fuel into the OM668 engine but this has a knock on effect with the air flow sensor.

It is not unusual that there's a limit in the air flow sensor MAF/MAP on the OM668 when loads more air is being drawn 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 was restricting bhp at a much lower level.

Intake manifolds flow the air from the air filter and allow it to be drawn into the engine cylinders.

Shape and flow rate of the Intake headers can make a big change to fuel delivery on the OM668.

On popular production engines plenum chambers are ripe for an upgrade, although a few OEM provide well optimised plenum chambers.

Increasing the OM668 valve size, doing a bit of OM668 port enlargement and head flowing will also improve performance, the fantastic side effect is it will raise potential for an improved performance increase on other upgrades.

OM668 performance cam tips.

Each engine responds better to mild cam durations so view each engine as unique.

The ECU mapping and fuel pump and injectors also have a large bearing on the torque gains you'll hit.

Longer valve 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 bhp gains are on offer for cam upgrades.

NB: Fast road camshafts normally raise the torque throughout the rpm band, you might lose a little low down bhp but higher rpm power will be higher.

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

A Competition cam won't do well if driving in heavy traffic.

You should ideally optimize your engines power to your driving style so for a car used daily stick with a shorter duration OM668 cam

Stage 1, 2 and 3 mods for the OM668

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 OM668 parts:

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

Stage 2 OM668 parts:

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

Stage 3 OM668 parts:

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

Remaps helps to establish the full potential of all the upgrades you've done to your OM668.

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 often differs on the upgrades you've fitted and the condition of your engine.

Turbo modifications on the OM668

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 OM668.

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 has a turbocharger upgrades are going to net you a larger power gain and most turbo engines are made using many forged and stronger components.

However engines have weakspots

See where you'll find these limitations and install stronger pistons, crank and engine components to cope with the power.

There are many guys spending a loads on turbocharger upgrades on the OM668 only to suffer the indignity of watching the motor literally blow up soon after it's first rolling road session.

Large capacity turbochargers tend to suffer a bottom end lag, and smaller turbochargers spool up really quickly but won't have the high rpm torque gains.

Thankfully the world of turbos is always increasing and we now see variable vane turbos, permitting the vane profile is altered according to speed to lower lag and increase top end bhp and torque.

Twin scroll turbos divert the exhaust flow into 2 channels and direct these at differently profiled vanes in the turbo charger. They also improve the scavenging effect of the engine.

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

Tips about fuel supply on the OM668

You will need to ensure that the engine is not starved of fuel so should pay attention to the fuelling when you start exceeding 20% of a bhp hike. Most tuners we speak with say to over specify your injector capacity.

As a rule of thumb add 15% capacity when fitting an injector, this allows for injector deterioration and affords a little spare capacity should the engine need 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 OM668 performance exhaust upgrades

We'd only recommend you look to boost your exhaust system with an upgraded one is if the current exhaust is actually causing a restriction.

On most factory exhausts you should find that your 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.

Sports exhausts increase the flow of gases through the engine.

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

Usual exhaust restrictions can be traced to the catalyst installed, so adding a better flowing high performance 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 OM668

Like most engines an OM668, 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 OM668, failure to do this will exacerbate engine wear, on a tuned OM668 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 OM668 why not pop over to the forums at TorqueCars where you can chat about OM668 tuning options and read about others projects who may be planning to do similar modifications on their OM668.

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This entry was posted under Makes and Models. Tags: engine, mercedes
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