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).
The characteristics and performance of a six-cylinder engine, comparing it to the Coshawk, 20 HP, and Hispano models.
| Identifier | ExFiles\Box 5a\5\ 05-page009 | |
| Date | 30th March 1927 guessed | |
| contd :- -2- The engine - a six cylinder - has a bore X stroke of 2.95" X 5.125" the swept volume being 3.444 litres or 10% greater than the Coshawk. The compression ratio is rather high being 5.9 /1 but the engine is not noticeably bad for detonations when operating on the dual synchronised ignition. Detonation is manifest at low speeds but we do not think as bad as the 20 HP. when running with a compression ratio of only 5.4 to 1. This engine possesses very similar characteristics to our own engines in being remarkably free from detonations when the cyl. jacket water temperature is cool - below about 40°C. It is found that the synchronised ignition besides requiring appreciably less advance than single ignition, reduces the tendency to detonate at low speeds. It will be remembered this characteristic was marked in the case of the Hispano as well as with our own aluminium Phantom with the turbulent type head. The power output and consumption curves are given on prints Nos. 4 and 5. The peak of the power curve occurs at approximately 2750 r.p.m. similar to the 20 HP. The B.M.E.P. curve rises to a maximum value at about 2200 r.p.m. giving 107 lbs/sq.in. This does not seem particularly high considering the high compression ratio because the Hispano gave 111 lbs/sq.in. with a 4.6 to 1 comp: ratio. It is however accepted by various authorities that the output per unit volume increases with increase of cyl. dimensions. contd:- | ||