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).
Engine performance test report for the Derby 30 HP car, analysing power curves with different configurations.
| Identifier | ExFiles\Box 5a\5\ 05-page185 | |
| Date | 10th December 1931 | |
| a.{Mr Adams} From Mr/ Hs{Lord Ernest Hives - Chair}/ Hr. c. to Mr. H.F. c. to Mr. C.R. c. to Mr. My. 857/76 RE/EM.3/G/10.12.31. x5090 EXTRA OUTPUT DERBY30 H.P.CAR. We have now had power curves off three further engines fitted with the higher compression pistons and cam- shaft to Sch.1543/S. We find that the figure of 82 B.H.P. given in No.49 is optimistic for this unit the mean open exhaust averaging out just below 80 B.H.P. (No.54). Though the peak B.H.P. is slightly higher open exhaust with a late timing, this is lost with the silencing system fit- ted (No 54 & 55) and therefore the earlier timing is pre- ferred as giving a slightly better low speed B.H.P. It will be seen from No.54. that though the loss with the S.U. open is negligible, with the S.U. closed about 5 B.H.P. is dissipated in the silencer. We found on the road that we obtained for the quietest exhaust system with the original small dia manifold and 1.6" inside dia down- take and front expansion box. Curve No.55 shews that we are no worse off with this combination than with the large manifold and 2" straight through pipe, curve No 57 we consider a very good average result giving the approved exhaust system, compared with the existing standard fitted with the old type exhaust system. We have taken to giving timings with .020 clear- ance because we find that with .015 clearance the results are erratic sometimes the tappet being just on and sometimes just off the toe of the cam. EM/HM.{Capt. W. Hallam - Head Repairs} Att: - No. 53 54 55 57 | ||