Where It All Started: Direct Injection and the 300SL Gullwing

Instantly recognizable by its gullwing doors and classic lines, the 300SL Gullwing (W198 I), and later on the 300SL Roadster (W198 II), are considered to be Mercedes-Benz icons. Originating from the 300 SL W194 racecar that premiered in the 1952 motorsports season, the 300SL Gullwing showcases incredible engineering accomplishments for the year 1954.

1952 300SL Coupe (W194) Racecar

1952 300SL Coupe (W194); The race-bred predecessor to the 300SL Gullwing and Roadster (W198)

The direct-injected M 198 inline six cylinder gasoline engine is slanted at a 45° angle inside a tubular space frame, providing the car with more than 200 hp and a lower center of gravity. Without any power adders such as turbo or supercharging, the 3.0L engine attributes its power rating to fuel being injected directly into the combustion chamber at high pressure using Bosch injectors.

M198 engine from a 300SL Gullwing showing injector and injection pump placement

The M 198 engine upright on an engine mount; the six Bosch injectors are visible from this angle as they are threaded directly into the engine block; the red caps keep dust out when fuel lines are not attached

Supplying these injectors with fuel is a Bosch mechanical fuel injection pump that was tuned to one of two engine configurations. One engine configuration has an 8.55:1 compression ratio, while the other is equipped with a “racing” or “competition” specification camshaft and has a 9.5:1 compression ratio.

The mechanical injection pump in this direct injection arrangement was so sophisticated for its time that 50 years later, the broader automotive industry still had not developed a system comparable in power, fuel efficiency, and emissions benefits.

To maintain 300SL Gullwings and Roadsters, the fuel injection pumps and injectors must be serviced to provide expected performance. Rebuilding and calibrating these components to Bosch factory specifications requires specialized equipment, application-specific knowledge, and experience with these sensitive, high-performance systems.

Bosch PES6KL70/320R2 fuel injection pump for 300SL Gullwing and 300SL Roadster

A Yankee Diesel rebuilt and calibrated Bosch PES6KL70/320R2 fuel injection pump ready for installation

Across the 1400 Gullwings and 1858 Roadsters produced, there were as many as a dozen different factory specifications for fuel injection pump calibration. For these situations, having original service documentation from Bosch is the only way to know the factory specifications and deliver a properly calibrated pump.

Bosch Fuel Injection Pump Documentation Sample for 220SE and 300SL models

Original documentation on the Bosch Einspritzpumpe (Injection Pump) for the 220SE and 300SL models

Since Yankee Diesel’s founding in 1991, we have provided rebuild and calibration services to specialty 300SL shops, restoration houses, and proud owners on many occasions.

1956 300SL Gullwing Coupe at 2015 Pebble Beach Concours D’Elegance

A 1956 300SL Gullwing Coupe presented at the 2015 Pebble Beach Concours D’Elegance

As these icons of automotive and engineering history continue to be enjoyed, we shall continue to serve the 300SL community with dedication and technical excellence. For more information on the 300SL fuel injection pumps we service, please visit our 300SL product page.


All pictures taken and owned by Yankee Diesel Inc.

Back to top