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 report comparing the horsepower and performance of different engine silencing systems.
| Identifier | ExFiles\Box 97\1\ scan0129 | |
| Date | 22th March 1938 | |
| -5- Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}1/WH.22.3.38. The summary of this work to date about which we are going to give a separate report when finished is that two separate silencing systems give a marked improvement in horse power over the single system; that dual downtakes are a slight advantage over a single downtake and that the 4 port system is slightly better than the 3 port system but not worth changing the head design for this reason alone. Summarizing in actual figures a 3 port system with two downtakes and two separate silencers gives a power loss to open exhaust of 8.75% and with the same 3 port system with a single downtake and silencer this percentage power loss is 22%. The actual comparisons are illustrated on the attached curves Y. D.{John DeLooze - Company Secretary} and E.{Mr Elliott - Chief Engineer} With these results in mind we consider that as per Jaguar the double system should be tried out on the road to see if passable for noise, and what these test bed horse-power gains mean to the ordinary customer on the road. Applying this to B.III engine the performance would be 114 BHP (max.) and 123 lbs/sq.in. MEP against present figure for B.III with single silencer of 102 BHP and 118 lbs./sq.in. MEP. Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} | ||