Editing Hyper engine (section)

===Hyper No. 1===

[[Samuel Dalziel Heron|Sam Heron]], head of development at [[Wright Field]] and a former colleague of Ricardo while Heron had been working at the [[Royal Aircraft Factory]], Farnborough, started working on the problem with a single-cylinder test engine that he converted to liquid cooling, using a [[Liberty L-12]] engine cylinder. He pushed the power to {{cvt|480|psi|MPa}} [[Mean effective pressure|brake mean effective pressure]], and the coolant temperature to {{convert|300|F|C|abbr=on|sigfig=2}} before reaching the magic numbers. By 1932, the USAAC's encouraging efforts led the Army to sign a development contract with [[Continental Motors Company]] for the continued development of the engine design. The contract limited Continental's role to construction and testing, leaving the actual engineering development to the Army.<ref name="White375">White p 375</ref>

Starting with the L-12-cylinder, they decreased the [[stroke (engine)|stroke]] from 7&nbsp;inches to 5&nbsp;inches to allow higher engine speeds, and then decreased the [[bore (engine)|bore]] from 5&nbsp;inches to 4.62&nbsp;inches, creating the 84&nbsp;in³ cylinder. This would be used in a V-12 engine of 1008&nbsp;in³ [[engine displacement|displacement]].<ref name="Balzer28">Balzer p.28</ref> They used the L-12's [[overhead camshaft]] to operate multiple valves of smaller size, which would improve charging and [[scavenging (automotive)|scavenging]] efficiency. Continental's first test engine, the single-cylinder Hyper No. 1, first ran in 1933.

They eventually determined that exhaust valves could run cooler when a hollow core filled with [[sodium#Metallic sodium|sodium]] is used—the sodium liquefies and considerably increases the heat transfer from the valve's head to its stem and then to the relatively cooler cylinder head where the liquid coolant picks it up.<ref name="Balzer28"/>

Liquid [[Internal combustion engine cooling|cooling systems]] at that time used plain water, which limited operating temperatures to about {{convert|180|F|C|abbr=on|-1}}. The engineers proposed using [[ethylene glycol]], which would allow temperatures up to {{convert|280|F|C|abbr=on|-1}}. At first they proposed using 100% glycol, but there was little improvement due to the lower [[heat capacity|specific heat]] of the glycol (about 2/3 that of water). They eventually determined that a 50/50 mixture (by volume) of water and glycol provided optimal heat removal.<ref name="Balzer28"/>