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).
The testing of different sparking plug positions on the 'Hawk' engine.
| Identifier | ExFiles\Box 33\5\ Scan101 | |
| Date | 27th June 1916 | |
| R.R. 535 a (400 Ph. C.S. 530 15-2-16) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 1548. EH2/DB{Donald Bastow - Suspensions}27616. June 27th 1916. To R.{Sir Henry Royce} from EH. c. to J.{Mr Johnson W.M.} c. to By.{R.W. Bailey - Chief Engineer} c. to E.{Mr Elliott - Chief Engineer} c. to Ep.{G. Eric Platford - Chief Quality Engineer} c. to Na.{Mr Nadin} X.No. SPARKING PLUG POSITION. 2025 We have fitted to the "Hawk" engine a set of cylinders which have sparking plug bosses in the side just under the inlet valve port. We fixed to the engine a double spark magneto and ran one set of wires to the standard position plugs on top and the other set to the plugs in the side. We could then by earthing the high tension current on either side get on accurate comparision. With the magneto set 25° when fully advanced, power at 1350 was 82 HP with the plug firing on top. With the plug firing on the side the power was 79.3HP. We found that to get the power equal with either position firing, the magneto had to be advanced 6 to 8°, more for the side plug. The side position of plug will not fire as weak a mixture inless the magneto is advanced. We could find no difference in slow running or as regards plugs oiling up. We have purposely run with an excess of oil but could not notice any difference. As regards pre-ignition, we find the side position is less likely to pre-ignition. The difference is only a degree, we can still get pre-ignition on the side position. | ||