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 loss caused by air-silencer and carburetter modifications.
| Identifier | WestWitteringFiles\T\2July1929-December1929\ Scan218 | |
| Date | 20th December 1929 guessed | |
| -2- of the cowling around the air-valve ports. The curve V.758 shews the power loss caused by this cowling, which amounts to 3.0% at 2500 R.P.M. Since fitting the standard air-valve, diaphragm and high speed choke, the metering was found to be approx. the same as on the standard carburetter. Attention was now directed to the air-silencer. When this was fitted to the modified carburetter the power loss was still 7.8% at 2500 R.P.M.,(see V758). If the loss due to the air-ports cowling is subtracted the air silencer is now responsible for 4.8%. To this we must add 2.0% (loss due to std. air intake), as explained above, making the silencer loss now a total 6.8%. It will be noticed that this is a higher figure than the loss caused by the silencer on the original carburetter. This increase is probably due to the extra amount of air with which it has now to deal. This 6.8% loss may be divided up between the parts of the air silencer thus:- centre tube (E79642) = 2.5%; second tube (E79645) = 1.5%; third tube (E79644) = 1.0%; fourth (outer) tube (E79643) = .5%; the remaining 1.3% being due to the end pieces (E79577/3). See V.759. The air holes in the concentric tubes of the silencer were now enlarged in area by 33%, which reduced the total silencer loss to 5.7%. Of this figure, the centre tube was still responsible for 2.4%; so the slots in this tube were enlarged still more to 94% of their original area. The complete modified carburetter now shews a power loss of 5.6% at 2500 R.P.M., which loss is diminished to zero at 1750 R.P.M. (see V.757). | ||