Pushing Performance Limits in a Mercedes-Benz Turbodiesel Jeep Rock Crawler
Calibrating Mercedes-Benz fuel injection pumps to Bosch factory specifications is standard procedure at Yankee Diesel Inc. When Chris Abele Sr. of Autowerks in Port Chester, New York came to us, he was building something unique and needed a uniquely tuned fuel injection pump. Knowing that Chris Sr. and his son, Chris Jr., are off-road enthusiasts that also specialize in European vehicles, standard procedures quickly became guidelines as we learned about the project’s needs. Fast forward to today: both Father and son have their own 4×4 Jeep rock crawlers with custom built roll cage, long-travel suspensions with DANA60 ARB solid axles, and a Mercedes-Benz double overhead camshaft inline 6-cylinder turbodiesel engine (OM606) with stock 5-speed automatic transmission (722.6) and electronic shift controller.
In the Mercedes-Benz and broader tuning communities, the turbodiesel OM606 engine and 722.6 5-speed transmission combination are considered very desirable for a number of reasons:
- Respectable maximum power and torque ratings with good fuel economy: 174 hp at 4400rpm and 243 ft-lb at 1600rpm while achieving 30+ mpg in the E300 TD sedan
- 24-valve double overhead camshaft inline-6 engine configuration was well balanced from a rotational harmonics perspective and considered by many Mercedes experts to be over-engineered
- The electronically controlled mechanical fuel injection pump (0400196003) can be replaced for one of the mechanically controlled versions most commonly used on the OM603 engines, which preceded the OM606. U.S. Bosch numbers for these pumps are listed below with links to detailed product pages. The benefit from this pump compatibility between OM603 and OM606 is that the mechanical pump is simpler to adjust fuel delivery volume and tune the engine for performance
- All 1998 and 1999 W210 E300 turbodiesels sold in the U.S. came equipped with the OM606 and 722.6 combination; these aging sedans are now becoming readily available as donors for drivetrain transplants
The goal behind this drivetrain transplant into a Jeep rock crawler is to maximize performance, fuel efficiency, and reliability. With the OM606’s reputation, the missing factor was performance as 174hp would be limiting in the 5500lb to 6000lb vehicle. The ask was for more fuel from the fuel injection pump to match the additional airflow from a larger turbocharger and intercooler installed around the OM606 engine.
There is no book for tuning the fuel injection pump on a Mercedes turbodiesel-powered custom built Jeep rock crawler
So began three years of fuel injection pump tuning on our side, and extensive on and off-road performance testing for Autowerks. The winning fuel injection pump required larger plunger and barrel assemblies to deliver more fuel. Sometimes referred to as fuel pump elements or simply pump elements, the largest inner diameter-size pump elements available from Bosch for these M-model pumps was 6mm. These precision machined pump elements in larger sizes (7.5mm and 8mm) are manufactured and available from a fuel injection shop in Sweden called Dieselmeken. These are not plug and play components because they require pump calibration and often other modifications to be beneficial in an application, which is why Dieselmeken and very select other shops offer fuel injection pump modification and calibration services.
With a set of Dieselmeken’s 7.5mm elements installed and the fuel injection pump calibrated at Yankee Diesel Inc., Chris Jr.’s rig was ready for further on-engine tuning, testing, and ultimately competition. Chris Jr. and his father took Chris Jr.’s rig to California to compete in the grueling 180-mile 2017 King of the Hammers race. They placed 7th in the 4500 class closely behind six veteran competitors (none of them diesel), and nearly three hours ahead of the 8th place finisher.
Years of effort in the shop and time on the trail culminated in a successful inaugural performance. If you ask Chris Sr., he credits many things, but always commends the reliability and capability of that OM606 engine, fuel injection pump, and transmission, which he races to this day unchanged from King of the Hammers. The same cannot be said for the heavy duty transfer case.