Modifications and test results for a 19-EX carburetter experiencing cutting out issues.
| Identifier | ExFiles\Box 11\4\ 04-page059 | |
| Date | 13th May 1932 | |
| To Hs {Lord Ernest Hives - Chair} /Rm. {William Robotham - Chief Engineer} From G.W.H. Hotel de France, Chateauroux(French test region), FRANCE. 13th May, 1932. RE CARBURETTER - 19-EX. We have tried out the modifications suggested in Hs {Lord Ernest Hives - Chair} /L.H.Swindall's memo. (1) Blanked 2 of the 6 - .039 dia top row diffuser holes. (2) Blanked 3 of the 6 - .055 dia bottom row of the holes. (3) Reset high speed jet. (4) Temporary well of petrol under diffuser. --- (1) These modifications have not altered our trouble of cutting out when accelerating from slow speeds, in fact it appears to be worse. (2) Our acceleration figures actually show us to be 1/5th of a second slower. (4) Well of petrol gave no results. --- We are of the opinion that you are confusing our trouble with slow running. This is not the case. What happens is that after braking down to a slow speed of 15 or 20 m.p.h., then open the throttle, not full, to get away, the engine turns over for a few revs gradually accelerating, then cuts out, appears to back fire, not in the carburetter. It almost causes the car to stop. We have got over this trouble by putting a spring under the air valve (attaching the spring to the valve). All this spring does is to lessen the weight of the valve for the first portion of its travel upwards, thus giving it a slightly quicker and earlier rise. This gives us the mixture that is required for the speed of the acceleration. At 30 m.p.h. there is a definite weak spot. This is apparently when the air valve is opening up the air port. After 35 - 40 m.p.h. the spring does not affect the operation of the valve. We have fitted the whole range of needles brought out, and the one we are now using is the largest, 2°.24. This gives us a better average at high speeds. We believe we could still have a slower taper as we have had no sign of weakness at speed. We hope to be able to demonstrate the fault of the carburation upon our return. G.W.H. | ||
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).