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).
Table showing the boiling temperatures in Celsius for different types of bonnet ventilation at various speeds.
| Identifier | ExFiles\Box 16\2\ Scan014 | |
| Date | 19th August 1921 guessed | |
| Figures given are temps. at which the Car will boil if driven for sufficiently long at full throttle under the conditions named. °C. Type of Bonnet Ventilation. All Out | 45 M.P.H. | 30 M.P.H. Vertical Louvres. 44.5 | 37.5 | 36.5 Three ventilating shutters per side. 41.5 | 33.00 | 32.5 No Bonnet Ventilation 38.0 | - | 27.5 Tests on 19-TX. Rad. used. small Hexagon U.S.A. Hexagon .305 across Flats. Centre .255 dia. round 18 dents. car weight. 48 cwt. Axle 11 X 41 Radiator dimensions 25.9 X 33.7 Radiator shutters fitted for all tests. Louvred Bonnet F.79291. Shutter Bonnet N. sch.3232 | ||