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).
Performance improvements and depression figures for the Phantom III induction system.
| Identifier | ExFiles\Box 93\4\ scan0107 | |
| Date | 24th February 1937 | |
| 319. ToE. from Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}9/AP.24.2.37. PHANTOM III. INDUCTION SYSTEM. As you know, the four port head has by cutting out the long and restricted manifold of the 6 port head improved the breathing, such that there is an appreciable increase in top speed power. This has increased the depression as measured in the manifolds to 4.5 - 5.0 Ins.Hg. which shows that there is a lot more power available if this figure can be brought down to 2.00 - 2.500 Ins.Hg., which is quite a normal kind of depression. We give below figures of the depression as taken at 4000 R.P.M. which is the approximate speed of max. power and at various points in the induction system, recently checked on a unit with the 4 port heads. | Condition. | Inlet to Hot spot taken in the insulating washer. | Immediate outlet from hot spot. | In main pipe of manifold between ports. | |---------------------------------------------------------------------------|---------------------------------------------------|---------------------------------|-----------------------------------------| | 1. Standard carb. and air silencer etc. | 3.45 | 5.2 | 4.7. | | 2. Horizontal vane in capacity of box both A.{Mr Adams} and B. side, otherwise as 1. | 3.6 | 4.8 | 4.2 | | 3. Air silencer removed otherwise as 2. | 3.3 | 4.4 | 3.7 | | 4. Air inlet horns deleted otherwise as 3. | 3.1 | 4.1 | 3.5 | | 5. As 4. but with 1 3/8 dia. chokes as against std. 1 5/16. dia. chokes. | 1.8 | 3.7 | 3.0 | continued | ||