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).
Results from three engine performance tests (A, B, C) and their corresponding curves.
| Identifier | ExFiles\Box 24\5\ Scan031 | |
| Date | 29th April 1925 | |
| R.R. 493a (50m) (D.B. 173 25-9-24) J.H.D. EXPERIMENTAL REPORT. -2- Expl. No. REF: Hs{Lord Ernest Hives - Chair}/ACL/LG29.4.25. TEST (A) CURVE 2. As would be expected we get a steady fall in the heat dissipated as the power on the throttle falls. The heat flow is a maximum for this speed where the throttle is full open and the power at its maximum. As before stated the exhaust is free in this test. TEST (B) CURVE 2. This curve again shows that the maximum heat flow occurs for the maximum power output and falls slightly as the power decreases with increases of back pressure. The test was taken at full throttle. A very reasonable explanation for the fall in heat flow with the decrease of power in this test - which on first thought one would imagine to remain constant - is that with increased back pressure a certain amount of exhaust gas is expelled into the induction pipe when the inlet valves open and is drawn in again with the fresh charge. This reduces the amount of fresh charge taken in per stroke and is clearly shown to be the case from examination of light spring indicator diagrams which we took some time ago in connection with another experiment. Another proof is that the induction pipe depression is lower with increased back pressure. TEST (C) CURVE 3. This curve shows that the heat flow to the water per B.HP. increases as the back pressure increases. As before stated this test was conducted at constant power (50 HP.) and constant speed (1500 r.p.m.) Therefore as the back pressure is increased to maintain same power and speed, we have contd :- | ||