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).
Summary of engine performance improvements achieved through various modifications to camshafts, compression, valves, and carburetors.
| Identifier | WestWitteringFiles\Q\2April1927-June1927\ 115 | |
| Date | 31th March 1927 guessed | |
| contd :- -5- the standard and long duration cams in positions of the best timing. The greater opening at and after bottom dead centre to take advantage of the kinetic energy of the gases built up during the earlier part of the stroke is clearly shewn. SUMMARY : -------- (1) A camshaft with long duration inlet and exhaust cams resulted in an increase in max. B.HP. of 21%. (2) The speed of max. output was raised from 2650 r.p.m. to above 3000 r.p.m. (3) The B.M.E.P. was increased from 120 lbs/sq.in. to 124.3 lbs/sq.in. and the speed of max. B.M.E.P. raised from 1750 r.p.m. to 2500 r.p.m. (4) To obtain the above advantage it was necessary to employ carburetters giving a low induction manifold depression. (5) A total gain of 30.5 HP. has been effected by :- (a) Raising the compression to 5.45 to 1. (b) Employing 1.400 dia. valves giving 40% greater area than std. when fully lifted. (c) Using two Zenith carbs. which lowered the induction pipe depression from 3.5 in. to .5 ins.Hg. (d) Using inlet and exhaust cams giving respectively 28º and 12º longer duration relative to the crankshaft. contd :- | ||