As with nearly all other German AFVs, it was planned to replace the Pz Kw III eventually with improved designs. The result of a works conference held on 25th May 1938 at Daimler-Benz was that they were to develop a new AFV of the 20-ton class for which a 400-hp engine would be required. The Army Weapons Department again proposed the use of Maybach petrol engine. How exclusively the German Armed forces were supplied with Maybach engines is shown by the fact that the company (plus licensees) produced during war years, nearly 140,000 engines of varying sizes, having a combined output of 40 million horsepower. Daimler-Benz suggested to the Weapons Department as an alternative the use of diesel engines of its own manufacture and decided to develop the MB 809 diesel engine for the VK 2001 (DB)-the proposed Pz Kw III replacement. This power unit was to be constructed with the same capacity as the Maybach HL 190 (a 12-cylinder petrol engine with a 19-litre capacity weighing 1000 kg) which was proposed by the Army Weapons Department.
Daimler-Benz, starting in June 1938 developed a V-12 diesel engine of almost 25.5 litres capacity and producing 400 hp at 2100 rpm. Continual alterations during the assembly of the vehicle demanded corresponding adjustments and alterations in the diesel engine design.
The four projects which had been worked on until mid-December 1938 produced the following results:
Daimler-Benz also experimented with the transverse installation of engines in order to save on overall length and weight of the vehicle. The tests showed no worthwhile advantage however. An attempt was also made to achieve a higher power-to-weight ratio by using welded steel cylinders, even though these were considerably more expensive to produce. The reduction in weight would have allowed heavier armour and smaller water and oil radiators could have been used.
Following the completion of the engineering developments at the beginning of June 1940 the first dynamometer run took place in February 1941, and the acceptance run of the first engine on 12th March 1941. This engine arrived at Marienfelde for installation into the test vehicle on 21St March 1941 after which cross-country tests took place on the proving grounds and in Kummersdorf.
Efforts to improve the performance of both vehicles and engines were made when, shortly after the start of the Russian campaign, it was discovered that the enemy was using considerably heavier vehicles and more powerful engines. The VK 2001 project and the diesel MB 809 engine were consequently cancelled.
Klöckner-Humboldt-Deutz AG of Cologne were busy at this time designing a diesel engine for the VK 2001. The contract for this power unit, issued by the Army Weapons Department, specified delivery by the end of 1941. The engine was to be an 8cylinder radial engine which was to produce 350 hp at 2500 rpm. A test vehicle was constructed but it did not go into production.