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).
Shortening an exhaust pipe to reduce noise, with comparative B.HP data.
| Identifier | WestWitteringFiles\N\2October1925-December1925\ Scan51 | |
| Date | 12th October 1925 | |
| R.R. 493A (50 H) (D.D. 31, 12-6-25) J.H.D. EXPERIMENTAL REPORT. -2- Expl. No. REF: Hs{Lord Ernest Hives - Chair}/AJL.2/LG121025. shows a slight advantage but it is safe to state that there is no disadvantage, the slight increase being possibly caused by some other outside influence. Owing to the disagreeable effect of this exhaust noise it is recommended that the pipe be shortened, the new length being 11.5" from the face of the flange to the end of the pipe. As this cuts out the ejector effect it is also recommended that the ejector baffle be dispensed with in future front silencers. As there is no disadvantage in leaving this in, it should not be necessary to remove it from existing silencers. B.HP. at Road Wheels. R.P.M. | Before shortening pipe. | After shortening pipe. 500 | 25.5 | 26.3 750 | 37.5 | 38.8 1000 | 48.3 | 49.6 1250 | 59.6 | 60.6 1500 | 69.3 | 69.7 1750 | 77.5 | 78 2000 | 82 | 82.5 3rd. gear. | lbs.lift. | lbs.lift. 2250 | 194 | 200 2500 | 170 | 174 2750 | 143 | 164 Hs{Lord Ernest Hives - Chair}/AJL. | ||