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).
Power curve graph comparing the India IV engine with a 5.1/1 compression ratio to a standard 20 HP production engine.
| Identifier | ExFiles\Box 5a\5\ 05-page031 | |
| Date | 28th September 1929 | |
| POWER CURVE FOR INDIA IV ENGINE WITH 5.1/1 COMPn RATIO. STD 20 H.P. PRODUCTION ENGINE SHEWN FOR COMPARISON CURVES CORRECTED TO N.T.P H.P. INDIA IV 5.1/1 C.R. STD PRODn 20 HP ENGINE. CEO/L / 28/9/29 | ||