page_title: Multi-valve
section_title: Aircraft
hierarchical_section_title: Multi-valve / Aircraft
caption_attribution_description: English: Sectioned view of the Rolls-Royce Merlin aero engine cylinders and valve gear. Taken at Royal Air Force Museum Cosford.
context_page_description: In automotive engineering a multi-valve or multivalve engine is one where each cylinder has more than two valves. A multi-valve engine has better breathing and may be able to operate at higher revolutions per minute than a two-valve engine, delivering more power.
context_section_description: Ettore Bugatti designed several multi-valve aircraft engines. The 1916 Bugatti U-16 1484.3 cid (24.32 L) SOHC 16-cylinder, consisting of two parallel 8-cylinder banks, offered 410 bhp (305 kW) at 2,000 rpm (12.5 kW/liter or 0.28 bhp/cid). Each cylinder had two vertical inlet valves and a single vertical exhaust valve, all driven by rocking levers from the camshaft. Other advanced World War I aircraft engines, such as the 1916 Maybach Mb.IVa that produced 300 bhp (224 kW; 304 PS) at altitude and the 1916 Benz Bz.IV with aluminium pistons and the 1918 Napier Lion (a 450 bhp 24-liter DOHC 12-cylinder), used two intake valves and two exhaust valves.
  Long after the King-Bugatti "U-16" aviation engine used them, shortly before World War II, the Junkers aviation firm began production of the Third Reich's most-produced military aviation engine (68,000+ produced), the 1936-designed, 35-litre displacement, inverted-V12, liquid-cooled Junkers Jumo 211, which used a three-valve cylinder head design inherited from Junkers' first inverted V12 design, the 1932-origin Junkers Jumo 210 — this was carried through into the later, more powerful 1940-origin Junkers Jumo 213, produced through 1945, the production versions of which (the Jumo 213A and -E subtypes) retained the Jumo 211's three-valve cylinder head design.
  The V12 engines of many World War II fighter aircraft used a SOHC configuration with four valves for each cylinder.
  An example of a modern multi-valve piston-engine for small aircraft is the Austro Engine AE300. This liquid-cooled turbocharged 2.0-liter (1,991 cc) DOHC 16-valve straight-4 diesel engine uses common rail direct fuel injection and delivers 168 bhp (125 kW; 170 PS) at 3,880 rpm (62.0 kW/liter). The propeller is driven by an integrated gearbox (ratio 1.69:1) with torsional vibration damper. Total power unit weight is 185 kg (408 lb).
caption: Cutaway view of 1941 Packard Merlin 28 V12 aircraft engine showing SOHC and four valves per cylinder. This widely used supercharged WWII engine produced 1,390 bhp (1,037 kW; 1,409 PS) from 1,649 cid (38.5 kW/liter).
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