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).
Power output tests for a 'Japan' engine, detailing findings on valve timing, carburettor setups, and manifold capacity.
| Identifier | Morton\M13.2\ img100 | |
| Date | 24th September 1931 | |
| To R.{Sir Henry Royce} From Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. to Da.{Bernard Day - Chassis Design} E.{Mr Elliott - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} Ha/Rm.{William Robotham - Chief Engineer}6/MJ.24.9.31. X5771. X50910 POWER OUTPUT - JAPAN. We have carried out a number of tests on 'Japan' with a view to obtaining information as to power output which might be useful on J.3. The first series of tests were conducted with a valve timing which proved to be one tooth too early for optimum power. Carburetter Disposition. Rm.{William Robotham - Chief Engineer}29. Shows the effect of trying two identical carburetters in ramming and non-ramming positions. Rm.{William Robotham - Chief Engineer}30. Shows the power output obtainable with various combinations of two carburetters. The two expanding (curve 3) carburetters were too small for this power output. The induction system used in each case is shown on the attached photograph. Induction Pipe Capacity. Rm.{William Robotham - Chief Engineer}34. Shows the effect of increasing the manifold capacity with the twin Zenith carburetter. At the conclusion of these tests the head was machined round the inlet valve as the unit was down in power. Effect of Valve Timing. After machining the head it was found that, although there was a slight gain in power, the unit was still below standard. The timing was therefore altered. Rm.{William Robotham - Chief Engineer}35. Shows the marked effect of varying the timing one tooth under these conditions. The results suggest what has already been proved on the old 3" bore 'China', that a long duration camshaft would increase the top H.P. on the 25 H.P. as on P.11. The fact remains that the existing 112° shaft is an excellent compromise for existing average conditions. It will be noted that this particular 112° shaft has some 6° less inlet duration than the theoretical figure. | ||