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).
Factors affecting engine overheating, such as bonnet ventilation, fuel mixture strength, and the use of a cut-out.
| Identifier | ExFiles\Box 24\5\ Scan307 | |
| Date | 1st August 1930 | |
| -3- (2) BONNET VENTILATION. - The two (or in some cases, four) bonnet shutters provided, drop the top water temperature some 3°C. when open at speed. They also keep the driver's feet cooler. Clearly it should be ascertained if these have been used when investigating an over-heating complaint. A bonnet fitted with louvres however is much more efficient in getting the hot air away from behind the radiator and also drops the top water temperature some 7°C. so that if the complaint of over-heating is really serious a louvred bonnet is essential. (3) MIXTURE STRENGTH. - It is not generally realised that mixture strength has a definite bearing on the radiator temperature. Weak mixtures are likely to cause trouble. If a Phantom II owner will run full strong when in danger of over-heating the top water temperature will fall some 3°C. (4) CUT-OUT. - When driving fast in hot weather the use of the cut-out is definitely advantageous in keeping the water temperature down and is worth about 3°C. From the results given it will be seen that the top water temperature can easily be 15°C. higher than it need be due to an ineffective fan belt and no bonnet ventilation. On the other hand if everything is 100% on the system, a Rolls-Royce car is very well cooled, in fact from tests we know that we are now on the Phantom II better cooled than the 'Hispano' which has always been held up as a model. As a general indication of efficiency, a Phantom II | ||