Section 5. Wartime Research and Production
Item 2. Diesel Engine Research
A layout plan of the Engine Test Shop on a diagram of the Koromo Plant test shop machinery placement prepared in March 1938 indicated the presence of a Krupp diesel engine and a Junkers diesel engine test bench. This suggests that diesel engine research had begun no later than the completion of the Koromo Plant.
The German-made Junkers diesel engine was an aircraft engine with an extremely unique structure: each cylinder was equipped with two pistons that operated in opposition to each other. The Krupp diesel engine was a Junkers engine modified for automobile use.
An article that ran in the September 1939 issue of the Ryusenkei, a Toyoda PR magazine, quoted Kiichiro Toyoda saying with respect to diesel engine research, "We are in the midst of many years of painstaking research, but we are beginning to see results and we are now conducting prototype research".1 In addition, the August 1939 issue of Kogyo Hyoron magazine reported, "Toyota Motor Co., Ltd. has long focused on the future potential of diesel automobiles and conducted prototype research in secret with the aim of creating its own vehicle modeled on the Junkers diesel vehicle. Toyota has now seen to the completion of the prototype and various rigorous performance tests are being conducted with a formal announcement planned for October ".2
The diesel vehicle, however, was never put on sale.3 A request was made by the industry and government agencies for restraint because of 'excessive competition', and there was no opportunity to launch a diesel vehicle.