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).
Comparison of power losses in pistons, connecting rods, and water pumps for 3½ and 4¼ litre engines.
| Identifier | ExFiles\Box 133\1\ scan0203 | |
| Date | 13th May 1937 | |
| -4- Slightly higher losses are experienced on the small bore unit than on the 4¼ litre engine. This is not quite what would be expected, but is probably accounted for by slight variations in piston ring loading. (6) Pistons and Conn.Rods. Figures in L.H.P. are:- R.P.M. 500 1000 1500 2000 2500 3000 3500 4000 4250 4500 3½ Litre. 0.32 1.06 2.12 3.40 4.96 6.80 8.71 11.00 12.20 13.39 4¼ Litre. 0.46 1.57 3.10 5.12 7.63 10.54 13.80 17.72 19.70 21.80 Losses here are some 50% greater on the large bore engine than on the smaller one, this being explained to a certain extent by the greater friction losses due to the increased inertia loading of the heavier pistons. On inspection, also, some of the big ends were found to be running rather tight, giving rise to a power loss, in this direction. (7) Water Pump Losses. R.P.M. 500 1000 1500 2000 2500 3000 3500 4000 4250 4500 3½ litre. .014 .076 0.234 0.45 0.88 1.45 1.98 2.83 3.30 3.70 4¼ litre. .033 .100 0.246 0.39 0.57 0.74 0.86 0.92 0.98 1.03 Losses are lower on the large engine which seems rather surprising as similar pumps are used on both engines. It may be, however, that due to smaller water passages the flow has been restricted, cutting down the pump delivery and lowering the power required, but as no water flow figures are available for the 3½ litre unit, it is not possible to verify this. In any case, however, the L.H.P. is very small, and relatively unimportant. (8) Balance. The remainder of the engine losses are made up of the crankshaft and camshaft bearings and gears, dynamo and drive, ignition contact breaker, oil pump and drive. continued. | ||