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 tests comparing single and standard manifold exhaust systems.
| Identifier | WestWitteringFiles\R\2December1927-February1928\ Scan010 | |
| Date | 6th December 1927 guessed | |
| contd :- -2- compared with 13 HP. experienced with the single manifold system. With the single manifold system the added restrict- ion of cutout closed results in a loss relative to open exhausts of 20 HP. at 2500 r.p.m. whereas the std. systems losses approx. 8 HP. Apart from the power loss we found much more heat was given out from the single manifold than the two std. manifolds. The air temp. round the carburetter rose to, and remained fairly constant at, 44°C. The air temp. with the std. system was only 21°C. We should mention however that the power losses quoted above are exclusive of this higher air temp., all readings being corrected for temp. and pressure. This would mean that the actual loss due to the single manifold would be greater than that shewn on the curves. Part of this high manifold loss was thought to be due to the exhaust from cyls. Nos. 5 and 6 opposing the general flow of gas from the remaining cyls. as was found to be the case in the std. 20 HP. exhaust system. We therefore altered the manifold as shewn on blue print No V.182 so that the exhaust from these two end cyls. joined the general stream in the downpipe. This alteration resulted in regaining about 5.25 HP. (see print V.181) but was even now 3.75 HP. less than the std. system. The venturi restriction at the bottom of the down pipe was removed and the down pipe diameter continued to the silencer but no appreciable gain in power resulted. Previous tests carried out with exhaust systems on the early Phantoms shewed us that for max. power a double mani- fold contd :- | ||