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).
Effects of turbulent and non-turbulent cylinder heads on engine power output.
| Identifier | ExFiles\Box 3\4\ 04-page342 | |
| Date | 21th May 1933 | |
| To E.{Mr Elliott - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. Sor. Rs.{Sir Henry Royce's Secretary} c. By.{R.W. Bailey - Chief Engineer} Da.{Bernard Day - Chassis Design} c. Hdy.{William Hardy} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}7/KT. 21.5.33. TURBULENT & NON-TURBULENT HEADS. We have frequently speculated as to the effect of the turbulent head on maximum power output. We cut a part of the turbulent head away on the Bentley keeping the compression ratio constant and did not get any measurable difference. Our last experiment on Peregrine before storing the units was to make a very careful comparison between four cylinder heads, two turbulent and two non-turbulent, having different sizes of valves. The high speed difference would probably have been increased with a long duration camshaft, but we shall not now be able to carry this test out. The results confirmed that the turbulent head does not lose much power with our existing valve arrangement and certainly permits of a .5 to .75 higher compression ratio for the same degree of detonation. We are not very surprised that there is less difference between the two heads when they are both fitted with large valves than when they are fitted with small valves, as we have recently come to the conclusion that we know very little about the flow of gas through the poppet valve at high velocities, and have had numerous results which indicate that small variations in the character of this flow produce an appreciable difference in the volumetric efficiencies of the engine. We are making investigations on this subject. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||