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).
Analysis of the Zenith triple diffuser carburettor induction system and its performance, including a plan view diagram.
| Identifier | ExFiles\Box 22\4\ Scan089 | |
| Date | 30th March 1927 guessed | |
| contd :- -3- but there is little reliable information available on the subject. Two horizontal Zenith triple diffuser carburetters each supplying three cylinders are used. The induction passages are cast in the cyl. block and consequently water heated. No balance pipe or passage is provided between the two induction passages consequently at high speeds there is a marked tendency for the fuel to blow back. Loss of fuel through this cause is however eliminated by means of covers over the intakes of the carbs - see sketch - which prove very effective as they entirely eliminate petrol spray outside them. Distribution is good at normal working temperature but there is a tendency for the two centre cyls. to be very slightly weak with a cold engine. Notwithstanding the good distribution, the fuel consumption (see curve 4.) is high, but this may be attributed to the rich setting of the carburetters which are not provided with a mixture control. The curves shewn were obtained with the same jets as fitted when taken from the car which xxxxx being of the 'sports' type would probably sacrifice economy for the sake of increase acceleration. Print 6. shews the induction pipe depression which is remarkably low and only .7" of mercury at the speed of maximum power. This is lower than on the F.10. while the Goshawk at speed of max: output is as high as 2.5" mercury. contd :- [Text from diagram] ZENITH CARB. DISTRIBUTING PIPE COMMON CHAMBER CYL 1. CYL 2. CYL 3. THROTTLE PLAN VIEW OF INDn SYSTEM. SEPARATE PORT TO EACH CYL. | ||