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).
Page detailing issues with engine scavenging, exhaust valve design, and high fuel consumption.
| Identifier | ExFiles\Box 54\4\ Scan049 | |
| Date | 25th September 1924 | |
| R.R. 493A (50m) (D.B. 175 25-9-24) J.H.D. EXPERIMENTAL REPORT. -2- Expl. No. REF: Hs {Lord Ernest Hives - Chair} /Rm {William Robotham - Chief Engineer} /LG5.9.24. so that for at least 15% of the stroke, exhaust gas was being blown into the reservoir. When, therefore, scavenging finally commences, there appears to be a probability of the air being mixed with exhaust gas. Owing to pumping losses, it was found impossible to get any power out of the engine with a higher scavenging pressure, otherwise this would appear to offer possibilities. The exhaust valve is of generous dimensions being 2.375" dia, but with a small lift - only .300". Its opening period is 174°. Its cam is peculiar in shape. Undoubtedly the valve, spring and cam would require re-designing for high speed work. From the excessive fuel consumption, which is over 1 pt/I.H.P/hr., one would be inclined to say that the exhaust valve closed rather too late, allowing mixture to be blown out. We did not obtain better results upon reducing the period by altering the tappet clearance, this, of course, inevitably reduced the lift and also delayed the opening of the valve. -------------------- contd :- | ||