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).
Dynamometer test comparison graph for various car exhausts and silencers.
| Identifier | ExFiles\Box 180\M4\M4.2\ img028 | |
| Date | 19th May 1921 guessed | |
| HUMBER. FREE EXHAUST. DODGE. FREE EXHAUST. HUP. - FREE EXHAUST. BUICK. - SILENCER FITTED. MARMON. - SILENCER FITTED. MIN: 1500 1750 R TAKEN ON DYNAMOMETER. | ||