Pistons in the Sky
The Mighty DB600 Series Aero Engines 1934-1945
 

Article Graham Robson
Images courtesy Daimler Archives
 
You can relax. This is not going to be a blow-by-blow account of a lengthy and ruinous war. Instead, it is a celebration of one of the most magnificent aircraft engine series ever produced – the DB600 V12 family that powered so many famous German military machines in the 1930s and 1940s.

And why am I writing about it in these pages? Mainly because it proves, yet again, that the company whose cars we all admire was also able to develop a series of magnificent engines in quite another market sector – aerospace. It also proves just how versatile the Daimler-Benz engineering team at Stuttgart actually was, for there is no doubt that many of the technicians who worked on the Silver Arrow race cars of the 1930s contributed to the design of the DB600 aero engines that followed. 

This story begins way back – a century, in fact – because even before World War I, Daimler and Benz had separately developed aero engines, with Daimler supplying petrol engines to Count Ferdinand von Zeppelin to power his airships. Both concerns supplied many engines during the war itself, but after restrictions enacted through the Versailles Treaty that followed, they were banned from producing aero engines of any kind for a number of years. But that was later.

As supplied in big numbers during the 1940s, the DB601 engine was an inverted V-12, a 34-litre unit complete with Bosch direct fuel injection developing 1,050bhp at 2,400rpm.

Earlier in 1929, the Reichswehrministerium (Germany’s Ministry of Defense), directed Daimler-Benz to begin work on a new, liquid-cooled, inverted V-12 piston engine. “Inverted,” by the way, meant the crankshaft was at the top of the engine and the two cylinder heads were at the bottom, below the 60-degree vee cylinder block/crankcase. Lubrication was always going to be a challenging problem, but company engineers soon solved that.

Front three-quarter view of the mighty 44.5-litre DB603 V12 engine.

The use of inversion, incidentally, was a directive from Ministry officials who wanted this engine to have a narrow top profile – to improve the pilot’s forward vision – and the exhaust outlets to be at a lower level. Mufflers? Don’t be facetious. It also meant – and think about this for a moment – that in due time, a larger-diameter propeller could conceivably be used because its axis was higher off the ground.

The original project design became the F4. By 1931, prototypes were running and the F4B followed, and in 1933, approval came to evolve the new DB600 out of this power unit. At this stage, however, one must note that fuel injection had not yet been adopted.

For many hard-boiled historians, the timing is significant. Not only was this the year in which Adolf Hitler came into power (and military spending on projects such as this engine soon increased), but it was also the year in which Daimler-Benz began to develop single-seat race cars for the 750kg Grand Prix formula. It is important to note that the first of the Silver Arrow engines – the M25A – was developed at the same time. Physically, the two engines had nothing in common, but in engineering philosophy – the use of four valves per cylinder, roller bearings supporting the crankshaft, and liberal use of light-alloy castings – they clearly came from the same design office.

Because of its purpose and the need to build in some “stretch” – dimensionally and in power increase – the DB600 was massive. Don’t forget that this brutally large and powerful engine was developed 80 years ago, so one simply must marvel at the ambition of design team members and their basic intentions. Not only did the original types, as fitted to fighter aircraft, produce 1,000 horsepower, but they weighed at least 1,650 pounds and were at least 80 inches long. Every inch of space between the cockpit and the propeller hub, therefore, was full of engine – a high-tech, complex, glorious-sounding and visually attractive power unit.

Admittedly, this was not the most powerful aero engine that Germany was developing at the time. BMW, for instance, was told to concentrate on radial units, which originally had air-cooled, two-row 14-cylinder layouts and produced a maximum of 1,600 horsepower. But no one doubted that the DB600 was the most elegant, space-efficient power unit yet seen in that ambitious country.

It was not, of course, the first V-12 aero engine for, to Germany’s chagrin, there was stiff competition from the UK. Even in the late 1920s, Rolls-Royce made many headlines worldwide with the performance of its R-type V-12s as used in the seaplanes that won the Schneider Trophy. And what became the legendary Merlin V-12 was developed in the mid-1930s as a smaller family version of that same R-type V-12.

To prove that its own V-12 engine was a masterpiece, Daimler-Benz introduced a highly tuned version of the DB600 in 1939 – the DB601, producing 1,800 horespower – and installed it in a specially prepared Messerschmitt Be 109 monoplane, which recorded the astonishing top speed of 469.2 miles per hour. This was a world air-speed record that stood until after the end of the war.

The original DB600 was, however, a splendid engine and absolutely right for the Messerschmitt Be 109 single-seater with which it was always to be associated, and did exactly what its designers originally expected – except for one important failing. As Rolls-Royce also discovered with the Merlin, the use of a carburetor for fueling purposes meant that in certain changes of direction – particularly when pitching the aircraft into high-negative-G maneuvers, the pilot could find the engine cutting out on him for a second or so, which was disconcerting, if not frightening, to say the least.

Rolls-Royce did not solve this problem for some years, but Daimler-Benz, along with its trusted supplier, Bosch, attacked the problem with vigor, restudied every idea they already had on fuel injection, and applied it to the DB600. Not only this, but they actually developed the process of direct injection – where the nozzles directed fuel directly into the combustion chamber rather than into the inlet passages – and the problem was overcome.

Fuel injection was a vital breakthrough – and greatly to the credit of Bosch and Daimlers-Benz – for, as any Merlin-powered Spitfire pilot would confirm, that second or two of hesitation due to fuel starvation could make all the difference in a dog fight.

The Dornier Do17 of the late 1930s evolved into the modernised Do217. and originally used DB601 engines, as shown here during workshop maintenance.

Like all the best engines – and I have already written about several other Daimler-Benz power units in these pages – the DB600 went on to have an illustrious career, not only in the Me 109, but in several other several successful aircraft. Even by 1945, when all else was lost, production still somehow continued at eight different factories all over Germany and – under license – at several sites in Japan.

Evolution was steady, indeed ambitious, and was accomplished within the confines of the original DB600 architecture. The DB601 of 1937 was the first major development, not only because of the direct fuel-injection feature, but because of sophisticated supercharger control. All DB601s were 33.9-liter machines, which produced 1,050 horsepower (more in certain developments) and before production ended in 1943 in favor of the DB603, more than 19,000 examples were produced. 

The Dornier Do 217 was a twin-engined bomber, powered by 44.5-litre DB603 engines, each producing a remarkable 1,750bhp at 2,700rpm

Not that this was enough for the planners, who oversaw the development of the DB605, which was a direct replacement for the DB601. Larger in displacement than before – it was now up to 35.7 liters, with a cylinder bore of 154mm and a stroke of 160mm – it had a new cylinder block (to allow for the bigger cylinder bores), and much more ambitious car-like valve timing (there were 105 degrees of overlap compared with 42 degrees on the DB601). Initial production offered 1,475 horsepower, but successive marks pushed this up to at least 2,000 horsepower. No fewer than 42,400 such engines were produced.

For even more heavyweight applications, however, the DB603 arrived in 1942. Within the same confines of the modified cylinder block/crankcase, it measured no less than 44.5 liters because of its increased bore and stroke over the DB605: DB605 – 154mm bore x 160mm stroke; DB603 – 162mm bore x 180mm stroke. The 603 was “Big Daddy” in more ways than one, for it was more brawny and ceded nothing to the smaller-capacity – relatively smaller, that is – DB601 and DB605 types. Even when originally produced, it delivered 1,750 horsepower for take-off – a whole lot more than any previous base-model DB. And according to one authoritative postwar dictionary, the special-type DB603N produced an astonishing 2,830 horsepower.

At the time, and for decades afterward, the ability of this single design continued to amaze Daimler-Benz’s rivals. Gas turbine engines were already on the way by the mid-1940s, but there is no doubt that this particular inverted V-12 stood then, and still stands today, at the very pinnacle of piston-engine development.

Nowadays, of course, there are few working survivors of this power unit, so if you get a rare opportunity to see one in action, take it. You might then align yourself with this writer, who is certain that what was achieved in the air in the 1930s and ’40s was all of value to the cars that followed under the Mercedes-Benz brand. 

A relatively early type of the DB600A, as fitted to the single-engined Heinkel HE118 fighter in 1939. This plane was soon superseded by the Messerschmitt Me109, which had a more powerful version of the engine.

HORSEPOWER RATINGS ARE QUOTED AT SEA LEVELS

 
ODDITIES

Derivatives of DB600 Series only partly developed by the time the war ended in 1945.

DB606: Composed of two DB601 engines mounted side by side & coupled. Designed for heavy-lift purposes, it developed 2,700bhp.
DB609: An inverted V-16 version of the DB603, with similar cylinder dimensions, rated at 61.8 liters/2,660bhp.
DB610: Like the DB606, but based on the DB605 dimensions, with 2,950bhp.
DB613: Like the DB610 but producing 3,800bhp.

At least another dozen off-shoots of the DB600 Series were produced, including diesels, some with two-stage supercharging, rotary valves, and  even a completely mad 36-cylinder ‘double-W’ layout  producing a massive 3,900bhp!

The DB605A was a major redevelopment of the basic DB601, this time with a 35.7 litre capacity, producing 1,475bhp at 2,800rpm. This excellent cutaway drawing shows the construction of the DB600-family of engines. Four valves per cylinder, single overhead camshaft per bank, and seven main crankshaft bearings–one can quite see where the experience already gained in ‘Silver Arrow’ GP race engines was used. Although the DB603 was a compact engine, it completely dominated the front-end structure of the celebrated Messerschmitt Me109 aircraft.