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 advanced valve timing at Top Dead Centre (T.D.C.) and its effect on residual cylinder and exhaust pressures.
| Identifier | ExFiles\Box 134\1\ scan0074 | |
| Date | 24th January 1938 guessed | |
| 3. there will still be some gas to be pushed out. In other words, if the valve shuts at T.D.C. there is bound to be a higher residual pressure than if the valve were still slightly open. To demonstrate this I advanced the timing so that the valve shut at T.D.C, and, using an exht. system which gave pressure below atmospheric during the latter part of the stroke, I took diagrams of pressures inside the cylr. & in the exht. pipe. It will be seen from Fig 1 that the pressure in the cylr. rises considerably above that in the exht. pipe. you will see that the cylr. press is a max. of 2 1/2 lb/in² over atmospheric at A & drops again before T.D.C. This drop is due to the fact that the inlet valve was well open, it being impossible to avoid advancing its timing when advancing the exht. Several diagrams were taken at other speeds & all confirmed the above finding. Diagrams taken with normal timing & a somewhat similar exht. system showed that the cylr. pressure followed the exht. pipe pressure very nearly. Fig 2. | ||