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The Mercedes-Benz OM606 Engine

Naturally Aspirated vs Turbocharged Engines

First off, we need to clarify a few things. There are two NA versions of these engines: OM 606.910 from W124 which came with a mechanically controlled injection pump and OM 606.912 from W210 which came with electronically controlled EDC injection pump. Both these pumps have 5.5 mm elements (although the EDC elements have a better design than the mechanical pump ones). Both these came with an organic head gasket. This graph from Wikipedia is very helpful.

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Turbocharged Engines

The turbo models (OM606.961, .962, .964) all came with EDC pumps with 6 mm elements, which are good for about 300 HP with a bigger turbo. They came with MLS (Multi Layered Steel). All OM606’s have piston oil squirters.

Power Levels

The .910 NA engine can handle around 300 HP. The .912 and turbo engines can handle around 450 HP on stock internals. In other words, you don’t need to upgrade anything inside the engine to reach this. Many think that all NA engines have weak rods. Only the .910 mechanical pump engines do. The  EDC equipped NA engines can handle more. Change the head gasket to MLS from a turbo model.

How do you reach these power levels? More boost (bigger turbocharger) and fuel (bigger element injection pump). Some think that you need a mechanical pump to do this, but EDC pumps are also able to be built.

EDC vs “Mechanical” Injection Pump

First off, both pumps inject fuel mechanically. They have a camshaft that is driven by the timing chain, which pushes the plungers up to force fuel to the injectors, which inject fuel into the prechambers in the cylinder head. The difference in these two types of pumps is how they are controlled. EDC stands for Electronic Diesel Control. Based on several sensors and inputs, a computer determines where to position the rack, which controls how much fuel is injected, which in turn controls RPM and power.

The other type, which is most commonly referred to as a “mechanical” injection pump, (which is technically incorrect, because they are both mechanical pumps, just one is controlled mechanically vs electronically) is controlled by a governor. A governor is a complex intertwined system of weights, springs and levers which controls the rack position. 

Both can produce a lot of fuel with bigger elements. Generally speaking, a mechanical pump is simpler because once configured properly, you simply move the throttle to control the engine. The OM606 then becomes a fully mechanical engine, which makes it a favorite for engine swaps into other vehicles. The downside is that you can’t fine tune like you can EDC. If the engine is staying in the original chassis, it’s better to keep it EDC. Some still prefer EDC when swapping, which can be done with a standalone converted ECU (such as those by Sean Treacy) or an aftermarket ECU, such as the DSL 1. It is a bit more complex, but more customizable. 

Power Levels and Necessary Upgrades

The earlier NA engines can handle about 320 HP on stock internals. The later NA’s that came with EDC pumps and the turbo engines can handle 500 HP on stock internals. EDC NA engines do not do well when they have high boost early in the RPM range and the turbo models aren’t much better. They are much happier with a little “laggier” (bigger exhaust housing) turbo. These engines like to rev. They do not make torque down low like most diesels.

Around 500 HP, the rods should be upgraded to forged rods

Mechanical pumps in stock form cut fuel around 5,200 RPM, but can be modified to reach over 7,000. EDC pumps are dependent on how they are configured. Stock ECU cuts fuel at 5,400 RPM, Stage 2 at 5,500 and stage 4 at 5,800. It’s assumed that they can go much higher if configured so on a DSL1.

The valve springs are not very stiff in stock form. Most don’t have any issues around 300 HP as long as your boost comes in at higher RPMs. But if you are using a smaller turbo and have early boost, you’ll need stiffer springs, even at sub 300 HP. We had bad valve float when testing a GTB2060 on a 6 mm pump because the boost came in so quick. Anything over 300 HP it’s recommended to upgrade the springs. The stock turbocharger will float the valves after 4,400 RPM.

The camshaft gears are pressed on and the crank pulley is held in place by a woodruff key. Both cams and crank need to be pinned or welded for high HP builds. Some have had issues with sub 300 HP, but it’s rare.

In general, the factory head bolts can handle the power, and don’t need to be upgraded. A common upgrade is to go with 12.9 bolts or drill and tap from the stock m10x1.5 to m11x1.5.

Injectors

Unlike direct injection diesels, the injectors do not need to be upgraded to make more power. They can flow all the fuel any injection pump can send them. However, since these engines are coming up on being three decades old, it is highly recommended to have your injectors tested for spray and pop pressure. If they are out of spec, and you plan on making more power, you want to increase the pop pressure, to 150 bars which we sell in both rebuilt and new condition.

The simple way to understand this is that Bosch set the pop pressure to 115 bar for naturally aspirated engines, and 135 for turbo engines. So we see that the more air pressure (boost), the higher the pop pressure should be. So if you are going above stock boost levels of the turbo engines, you want a higher pop pressure, which we recommend 150 bar.

Fuel and Boost Chart

The following chart can be used as a rough guide. Several factors come into play. This is very general.

Turbo Options

HP

Fuel (CC)

Boost (bar)

90-100

250-300

300-350

100-120

1

Holset HE250, Garrett GTX2867R 0.63, T04E 0.63

Holset HE300, HX35, Garrett G25-660

120-140

350-400

Holset HE351, Garrett GTX3076R, Precision 5431

140-160

400-450

Garrett GTX3076R, Borg Warner S257SX-E

2

450-500

160-170

Precision 6176, Borg Warner S362SX-E

500-550

170-190

Garrett GTW3476r, Borg Warner S364SX-E

550-600

190-200

Garrett GTW3684R, Precision 6776

600-650

3

>200

(Remember that boost doesn’t directly correlate to power, it comes down to air density/volume)

Power Increase Steps/Upgrades

An OM606 turbo engine (6mm EDC equipped) can make around 300HP with nothing more than a ECU tune and bigger turbo. We suggest our Hybrid Turbo, or a full turbo kit if you are running it in the 98-99 E300 W210. To make more power, you need more fuel, which means a bigger element injection pump. The stock 722.608 transmission can’t handle much over 300 HP. The stock exhaust manifold should be upgraded around the 350 HP mark.

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