OM606 Injection Pump Guide – Elements, RS Camshafts and Pop Pressure Explained

OM606 injection pump selection, element sizing and camshaft profiles are the foundation of any serious diesel performance build. Today we walk through how the injection pump works, what elements to choose and why communication with your pump builder is everything.

Mechanical vs EDC – Both Are Mechanical Pumps

Every injection pump in the OM60x family from OM601 through OM606 is a mechanical pump. The EDC pump has an electronic actuator moving the rack instead of a cable and throttle pedal but internally the pumps are identical. If the EDC electronics fail completely the rack can be pushed manually with a screwdriver to get home. Two mechanical pumps with different actuation methods. Nothing more.

Pump Element Sizes – The History and Current Options

The element is the component inside the pump that meters and delivers fuel. Element size determines maximum fuel delivery capacity.

Stock 5.5mm elements – original specification, good for approximately three horsepower per element. Completely inadequate for performance use.

6mm elements – found in some turbo applications, good for approximately 94 horsepower in ideal conditions. The sweet spot for six millimetre elements in a real world build is around 220 horsepower. Some claim higher numbers but 220 is realistic for sustained reliable use.

The performance element market began in Finland. A builder obtained Ford Transit seven millimetre elements and fitted them to a Mercedes pump. The results – including considerable black smoke – spread quickly online. Those Transit elements were not designed for turbo diesel applications and did not flow correctly for this use. But the concept was proven and development began.

The Finnish manufacturer developed proper seven millimetre turbo elements with correct helix angles and flow characteristics for turbocharged applications. Then eight millimetre elements followed. The eight millimetre elements from this manufacturer are the best available for maximum power applications. More aggressive fuel delivery, more power, more smoke potential if not managed correctly.

Diesel Mekano in Sweden took a different development path. The pump mechanic there has decades of experience and an extensive test bench. Through years of testing different helix angles, fuel pressures and element designs the ATLF and ATLF4 eight millimetre elements were developed. These elements are slightly less aggressive than the Finnish eight millimetre units – more fuel than seven millimetre, excellent driveability, the best choice for a high performance daily driver build. Numerous iterations were tested and rejected before the current specification was reached.

For most builds the recommendation is clear: low RS pump with eight millimetre ATLF4 elements. This combination gives excellent power, good drivability and strong reliability.

RS Camshaft Profiles in the Pump

The injection pump contains its own camshaft that drives the elements. Different camshaft profiles change the injection characteristics.

Low RS – gentle injection, good fuel distribution across the RPM range, excellent for daily driven builds at any power level. Cheaper than high RS pumps. This is the correct choice for the vast majority of builds.

High RS – more aggressive injection characteristics, suited to higher power applications where injection timing and aggressiveness need to match extreme boost levels.

200 RS – racing only. Not suitable for street use. The RS201, RS202 or RS203 pump for street use is a waste of money and the wrong tool. One builder in five thousand needs this specification. The rest do not.

The strange market reality is that low RS pumps are cheaper despite being correct for almost every build. High RS and 200 RS pumps command premium prices despite being wrong for most applications. This will not change by being pointed out but it is worth understanding before spending money.

On EDC pump builds the camshaft profile can be partially compensated through DSL1 PID configuration and pump mapping. This gives additional flexibility that mechanical pumps do not have.

Tell Your Pump Builder What You Want

This is where most builds go wrong. The pump builder is not a mind reader. If you send a pump without specifications the builder builds to their standard specification. That specification may be excellent. It may also be completely wrong for your application.

Write down exactly what you want before sending the pump:

• Power target
• RPM range
• Daily driver or race use
• Boost level
• Full fuel RPM target
• Any specific driveability requirements

Include this note with the pump. The builder will build to your specification instead of their standard. The result will match your build instead of being a compromise between your needs and their assumptions.

Injector Pop Pressure

Stock pop pressure is 135 bar. Most builders run 150 bar as a proven and well tested upgrade. Testing conducted at 10 bar increments from 135 to 220 bar showed consistent improvements with higher pressure up to a point. 170 bar is the preferred setting for built engines based on this testing.

Recommending stock 135 bar pop pressure for a performance build makes no sense. The improvement at 150 bar is real and well documented. At 170 bar the results are better still. Anyone recommending staying at stock pressure has not tested alternatives systematically.

Summary

• OM606 injection pump: both mechanical and EDC pumps are mechanical – only actuation method differs
• Element evolution: 5.5mm stock → 6mm turbo → 7mm performance → 8mm maximum
• Finnish manufacturer eight millimetre elements: highest fuel delivery, best for maximum power
• Diesel Mekano ATLF4 eight millimetre elements: excellent power with superior drivability – best for performance daily builds
• Low RS camshaft profile: correct for virtually every build, cheaper than high RS, better drivability
• 200 RS: racing only, wrong for street use regardless of power level
• Always specify your requirements in writing when sending pump for rebuild
• Pop pressure: 150 bar is the proven upgrade, 170 bar preferred for built engines

Seven countries in five days. See you later!