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 wear observations, carburation experiments, and fuel consumption tests.
| Identifier | ExFiles\Box 127\4\ scan0082 | |
| Date | 28th September 1937 | |
| -3- Rml/R.28.9.37. Taub told us some astonishing things about cylinder bore wear, one was that on a particular engine the bore wear was altered six times due to an alteration in the mixture ratio from 12 to 14 to 1. This is somewhat difficult to believe. Another observation was that cylinder bore wear had been increased 300% by having 4" too much ignition advance. Taub has got into a certain amount of trouble owing to the fact that the E.N.value of material, out of which English pistons are made is about 14,000,000 against 8,000,000 of the corresponding U.S.A. material. The result of this is that when rings are made in England to American practice they are very much stiffer than they are intended to be. This makes plain why we have never seen eye to eye with Taub. (5) Carburation. Taub has been doing some very intensive work in order to give a new 10 H.P. Vauxhall good petrol consumption. We have had one of our testers over there for three days working with the Vauxhall testers to see exactly how the result has been achieved. As soon as we have cleared up all the teething troubles on the Wraith engine, we are going ahead to see what we can do. Taub mentioned the astonishing figure of 70 m.p.g. at 20 m.p.h., and 45 m.p.g. at 60 m.p.h. on this little car. One of the discoveries he made during the test was, that if a Venturi was cocked over 8 thou. in a carburetter it would make 20% difference to the mixture ratio on certain cylinders due to spoiling the distribution. Taub is adopting positive choke closing for starting. As soon as the engine fires, the manual control which is spring loaded for the last half of its travel is released and then an 8 to 1 mixture is provided on which to warm up. When the engine is warm the control is pushed in completely, which gives the normal running mixture. This is a very simple scheme, and we are making some tests to see if it is adaptable to the Wraith. | ||