Engine modifications to achieve 75 B.HP and the results of exhaust system tests.
| Identifier | ExFiles\Box 5a\5\ 05-page218 | |
| Date | 1st November 1922 | |
| -4- LBA/A3.1/AE.11.22 contd. have increased the chokes and air ports by 46%. This higher curve giving a maximum of 75 B.H.P. with open exhaust represents what we could obtain without much modification to the standard production China(Experimental Engine) engine. The modifications made to obtain this power output were :- (1) Compression ratio raised to 5.25/1. (2) Inlet and exhaust valves increased to 1.400 dia. and port diameters increased. (3) Induction passage through the cylinder block increased to 1.200 dia. tapering to 1.500 at each end. (4) Standard 20 HP. carburetter with chokes and air ports increased by 46%. We do not think the camshaft modification would be necessary. All our tests so far have been made with open exhaust, but we know from previous tests with various exhaust manifolds on the old small bore engine when it was boosted up to high power, that the standard manifold reduced the open exhaust figure by 13%. We think this will be even more pronounced on the large bore engine but are making a test to determine the actual value. It was also found during the above mentioned tests that the three branch manifold - similar to that used on Phantom II engine - gave a power reduction of only 5%. | ||
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).