The Maybach Mb IVa was a water-cooled aircraft and airship straight-six engine developed in Germany during World War I by Maybach-Motorenbau GmbH, a subsidiary of Zeppelin. It was one of the world's first series-produced engines designed specifically for high-altitude use. It was quite different engine design than the previous Maybach Mb.IV, not just a simple modification.
Design and development
Like all engines of that time, the previous Maybach design, the Mb IV, lost as much as half of the nominal power of 240 horsepower at high altitude. The new Maybach Mb IVa of 1916 was the first engine designed to overcome this limitation.[1] It did not use a supercharger, but a much more primitive solution. The engine had purposely "oversized" cylinders, and a significantly higher 6.08:1 compression ratio. It was tested on Wendelstein (mountain)[2] at an altitude of 1800 m and rated there at 245 hp.[3] This would theoretically correspond to rating of about 300 hp at sea level; however, the engine was not designed to withstand such power[4] - it needed to be carefully throttled down at low altitude, so it would not exceed the safe level of 245 hp. It had three carburettor settings, to be changed during the flight depending on the altitude.
The engine was falsely given a rating of 260 hp (190 kW) at sea level, so it would not appear inferior to the engines it replaced.[4]
Other Maybach engines
The earlier Maybach engines were:
- Maybach AZ of 1909: 140 hp (100 kW)[3]
- Maybach CX of 1915: 210 hp (160 kW)[3]
- Maybach DW and IR of 1914: 160 hp (120 kW)[3]
- Maybach HS (there was a variant HSLu, known also as HS-Lu) of 1915: 240 hp (180 kW)[3]
- Maybach Mb III - a new designation for the existing Maybach IR engine[5]
- Maybach Mb IV - a new designation for the existing Maybach HS engine[5]
The power ratings for these older engines are at sea level, unlike the rating of the Mb IVa.
