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).
Investigation into the cause of 'Induction Roar' and tests to reduce it by altering valve design.
| Identifier | ExFiles\Box 48\4\ Scan020 | |
| Date | 13th October 1921 | |
| X.4227. Extract from Hs{Lord Ernest Hives - Chair}3/LG13.10.21. INDUCTION ROAR X.4227. We have carried out further tests in connection with this and feel fairly convinced that the noise doesnot come from the induction passages. We have made all kinds of temporary alterations to the passages which have not made the least difference to the noise. The noise comes from the air or gases passing through the valve. We have carried out tests by altering the shape of the valve, making it mushroom shape instead of the tulip shape. We found that this did make a definite reduction in the mount of noise. We have also tried reducing the diameter of the head of the valve, leaving a very narrow seating of about .030". We found that this also made an improvement. These tests show that the critical point is the gas passing the valve. So far our tests have only been carried out on one cylinder. We are now making a set of inlet valves to see the effect. H s. If we have discovered the root of the noise, it would be worth while persevering to obtain the minimum amount of noise at this point because there is no doubt that all cars make this noise more or less. | ||