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).
Cylinder head comparison tests carried out on vehicle 28.G.V.
| Identifier | ExFiles\Box 101\2\ scan0150 | |
| Date | 31th October 1936 | |
| K500a HOTEL DE FRANCE, CHATEAUROUX, Indre. France. GWH{George W. Hancock - Head Chateauroux}/HFH{Hoppy F. Hamilton}/S/JAB. 31st October 1936 To. Rem. C.W.H. Report on Cylinder Head Comparison Tests carried out on 28.G.V. These tests have been carried out with the greatest possible accuracy. Each result shown in the accompany-ing set of performances being the mean of four runs - two in each direction. The fuel used being "Esso" taken from the same pump. The road was dead flat and stretched just over one mile, giving the car a fair chance to gain full maximum speed. We would point out however, that our results were taken from the speedometer and not by stop watch. Weather conditions were on the wet side and therefore should not have effected the detonation results obtained. A full range of readings is given from 10° ADV. BTDC. to 17° BTDC. so as to leave no loop holes for queries. Both heads were cleaned up and valves lapped in before tests were started, and the new set of plugs fitted. We also show diagrams of roughness taken from 5 MPH. in top gear, up to approximately 20 MPH. This was done on a rig previously described and the results obtained conform to the personal feel in the driver's seat. The small red dot on each diagram indicates the point at which the accelerator was fully depressed. The section on each diagram before the red dot is shown, indicates the initial engine roughness or movement while running at 5 MPH. prior to fully depressing the throttle. It will be noted from this, that in each case the turbulated head is considerably rougher. While the engine is gaining speed from 5 MPH. upwards, the rough-ness dies down till the line is comparatively even. It will be also noted that in the case of the deturbulated head the line smoothes out at an earlier stage than the corresponding diagram for the turbulated head, showing a distinct advantage. This we can call advantage (One). By carefully considering results and by process of elimination, a fairly accurate idea can be gained as to the qualities of the engine when one or other of the heads combined with a particular governor is used. Considering power output at lower speeds, i.e. pick-up from 5 to 40 MPH. it will be noticed that the car, by use of the turbulated head invariably reaches 40 MPH. in a shorter time than the deturbulated head irrespective of governor, at the same time the detonations are slightly more prolonged and rather more noticeable in intensity, and the rough-ness is more pronounced. In our opinion, it will be preferable to eliminate detonations as much as possible, and sacrifice a little power, rather than have a slightly better get-away accompanied by loud detonations and roughness, particularly as the time taken to reach 40 MPH only varies by approximately one | ||