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).
Carburetter performance, detailing a weak spot causing engine 'popping back' and analysing mixture characteristics.
| Identifier | WestWitteringFiles\M\2Jan1925-March1925\ Scan24 | |
| Date | 25th September 1924 | |
| R.R. 493a (50m) (D.B. 175 25-9-24) J.H.D. EXPERIMENTAL REPORT. -3- Expl. No. REF: He/ACL/L.G15.1.25. The weak spot is very marked. It causes uneven running and if the engine is accelerated from this spot "popping back" through too lean a mixture invariably occurs. The speed at which this weak spot is at its maximum depends upon the load, and on a smooth level road it is about 30 m.p.h. Metering of carburetter under full load conditions :- The curves show that under full load conditions the mixture strength does not remain strictly constant but for a given air valve spring this fault can be easily remedied by slight modification of the shape of the extra air ports. The extreme lower speeds of these full throttle curves should be accepted with reserve because they are influenced to a large extent by distribution. For all these tests we define the 'correct mixture' as the weakest which will just maintain maximum torque although chemically this would probably be considered slightly rich. Therefore we see that the general characteristics of the EAC. carburetter are :- It does not supply a proportional mixture when running at light loads slow speed, i.e., at low depression. This lack of proportionality gives erratic running and becomes very pronounced when the engine is cold. The carburetter is quite good at full load i.e., at higher depressions. In other words, its performance on the car at light loads, low speed, does not compare favourably with the 40/50 HP. contd ..- | ||