From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Engine performance comparing increased compression ratios, detonation, and various ignition configurations including single, dual, and synchronised.
| Identifier | WestWitteringFiles\P\October1926-November1926\ Scan013 | |
| Date | 18th September 1925 guessed | |
| Contd :- -3- head, whereas previously this clearance was .128. This resulted in raising the compression ratio from 4.45 to 1 to 4.69 to 1. In addition the piston was slightly flattened so as to remove the bevel at its circumference to give as little free gas space between the piston and head as possible. The results were precisely the same except that detonation was increased in intensity in much the same degree as it increases in the standard engine with increase of compression ratio. The spark advance required - which should be an index to the turbulence - remained the same. The appended print gives the power output compared with the standard engine. Other curves give the minimum ignition advance required with single and synchronised dual ignitions compared with that required by the standard engine also having the two plugs synchronised. It will be remembered however that syn- chronised ignition on the standard engine gives no appreciable different results from those obtained with single ignition either with regard to detonation or advance. Some other tests were taken showing the variation of the B.M.E.P. with the ignition timing for synchronised and a single ignition. The ordinates on these curves are given as lbs.lift on the dynamometer. No.1 curve shews that when using singly either right or left hand side plugs, each are practically as efficient which was not found to be the case with the previous opposed plug Phantom (10 EAC. special) where the plugs on the carburetter side required more advance than those contd :- | ||