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, focusing on engine idling qualities and the effects of spark retarding.
| Identifier | ExFiles\Box 101\2\ scan0155 | |
| Date | 4th November 1936 | |
| 5009 HOTEL DE FRANCE, CHATEAUROUX, Indre, France. GWH{George W. Hancock - Head Chateauroux}/HFH{Hoppy F. Hamilton}/4/JAB. 4th November 1936 To. Rm.{William Robotham - Chief Engineer} G.W.H. 22. G.{Mr Griffiths - Chief Accountant / Mr Gnapp} V.{VIENNA} Re your memo Rm.{William Robotham - Chief Engineer}7/MJ.2.II.36. Further to our report on cylinder head comparison tests, although we have duly made a note of the idling qualities we regret that we omitted to include them in the complete report. Idling in each case showed very close relations with the slow running qualities, as were shown in the diagrams. If the bonnet were raised and each head examined in comparison, the Turbulated head produced slightly more pronounced engine torsional vibrations as against the vibrations produced by the Deturbulated head, but the actual r.p.m. showed little if any difference, and we are of the opinion that a driver could not distinguish any difference in the two heads as far as idling is concerned. We have spent some time in drawing up conclusions as to the possibilities of retarding the spark from 13° B.T.D.C. in order to obtain better idling results. We find that the engine idles a little slower if the hand control is retarded by 9 notches, i.e. equivalent to 7° making the initial advance 6° B.T.D.C. If retarded any further, the engine starts pounding and produces a tinny note from the exhaust. We also note that although the engine runs slightly slower with the hand control retarded 9 notches, we are unable to detect any smoother or rythmatic idling. We have also checked up the effect that this retarding has on slow running performance. The best possible slow running obtained with 13° ADV was between 6 & 7 MPH, and by retarding the hand control 9 notches, i.e. 7° on the flywheel, we were unable to reduce this speed, and it was not until the hand control had been brought 18 notches of the way down the quadrant that any noticeable difference was obtained, viz. one and a half MPH. slower bringing the speed down to just over 5 MPH. Although the pounding note is noticeable, when standing by the side of the car one cannot hear any change inside the driver's seat, unless standing by a wall with the windows open. ----------- GWH{George W. Hancock - Head Chateauroux}/H.F.H. [Signature] | ||