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).
The performance and fuel economy of car 7 CA, detailing carburettor settings and potential engine improvements.
| Identifier | ExFiles\Box 180\M3\M3.3\ img013 | |
| Date | 12th March 1918 | |
| To EH. from R.{Sir Henry Royce} Copy to GJ. ORIGINAL X.682 RE 7 CA. We had occasion the other day to use 7 CA, and with hard roads and well pumped up tyres the car appeared to be doing 17 or 18 miles to the gallon - a short run to the Station and back at a high average speed. In addition to the improved condition of the road, and the much tighter tyres, the carburettor jet was set so that the low speed was decidedly weak in the normal position, and the high speed jet was fully strong. As far as my experience has gone, this has always been the best way to obtain economical petrol consumption, and I think the car as it now stands is wonderfully good in this respect all round. You will remember that it has the more vigorous engine through the higher lift valves and somewhat higher compression. The only thing I can suggest to improve it will be the slower moving air valve. which I am expecting you to send me. R.{Sir Henry Royce} | ||