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).
Experiments with compression ratio and exhaust system on a 20 HP engine.
| Identifier | WestWitteringFiles\O\2April1926-June1926\ Scan077 | |
| Date | 1st May 1926 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/ACL. c. to BJ. RG.{Mr Rowledge} c. to E.{Mr Elliott - Chief Engineer} EY. c. to DA.{Bernard Day - Chassis Design} Wor.{Arthur Wormald - General Works Manager} ORIGINAL Hs{Lord Ernest Hives - Chair}/ACL1/LG1.5.26. EXPERIMENTS WITH COMPRESSION RATION AND EXHAUST SYSTEM ON 20 HP. ENGINE. X5230 X. 4134 The following report describes some experiments we have carried out on the 20 HP. test engine, and cars, with higher compression ratio also analysis of the power losses due to different parts of the exhaust system. COMPRESSION RATIO. We are able to make a close estimate of the power gained for a given increase of compression ratio and the object of these tests were to determine if, with ordinary fuel, an appreciable increase in power was attainable by this means without attendant disadvantages of detonation and pre-ignition which would impose a natural limit on the power possible. The ratio was increased from 4.75 to 1 (std.) to 5.45 to 1, by addition of metal to the top of the present piston casting as indicated in the adjoining sketch. With regard to power this was found to give us an increase of 10 % or 6 HP. at 3000 r.p.m. and bring our maximum up to 61.5 HP. These figures represent maximum values as they were taken with free exhaust having only short pipes - 8" long - at each exhaust port. contd :- [Text from blueprint sketch] .212" HEIGHT OF HEAD RAISED | ||