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).
Analysis of engine component losses including pumping, tappets, and piston rings for 3.5 and 4.25 litre units.
| Identifier | ExFiles\Box 133\1\ scan0202 | |
| Date | 13th May 1937 | |
| -3- It will be seen that there is a very appreciable gain over the small bore unit which is only to be expected, comparing the 1 5/8" system against the 1 3/8" system. At the same time, however, the actual mechanical loss is so small as to be negligible. (3) Pumping Losses. These were obtained by removing the valves and plugs and all the valve gear down to the bottom tappets, the oil being blanked off from the rockers. R.P.M. 500 1000 1500 2000 2500 3000 3500 4000 4250 4500 3 1/2 litre. 0.60 0.91 1.40 2.44 4.06 6.03 8.62 11.60 13.35 15.15 4 1/4 litre. 0.98 1.79 2.93 5.20 8.55 11.32 16.55 23.00 26.60 30.60 It will be observed that the pumping losses in the large bore unit have been increased by over 50% on the small engine, giving rise to quite a substantial power loss. This extreme difference is put down to the fact that though the flow of gas and air to the engine has been increased by nearly 16%, the inlet ports remained unaltered from the size used on the 3 1/2 litre, thus causing a considerable restriction. This point has since been modified to give a uniform diameter of 1.625" giving a very useful power gain. (4) Bottom Tappets. These losses are very small and not worth detailed consideration. (5) Piston Rings. Comparative L.H.P. figures are:- R.P.M. 500 1000 1500 2000 2500 3000 3500 4000 4250 4500 3 1/2 litre. 0.38 0.93 1.70 2.60 3.54 4.45 5.40 6.34 6.85 7.26 4 1/4 litre. 0.33 0.91 1.71 2.55 3.42 4.24 5.00 5.76 6.06 6.35 continued | ||