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).
Enquiry into the cause of fires on Bentley cars, related to S.U. carburettor flooding.
| Identifier | ExFiles\Box 3\6\ 06-page161 | |
| Date | 5th May 1934 | |
| To Mr. [redacted] and Mr. [redacted] From E.{Mr Elliott - Chief Engineer} c.c. Mr. [redacted], Mr. [redacted], Mr. [redacted], JHS. re Fires on Bentley. With reference to memo C23/0.1.5.34, I have now held an enquiry into this matter and as a result of the experience we have now had on production it can be said that the S.U. carburetters are found to be subject to flooding at times. This flooding is not the gentle drip we have experienced with our own carburetters in the past but a considerable flow, and the evidence is that if the needle is partly off its seat such as it might be due to the presence of a piece of grit, petrol is emitted from the ventilation holes on top of the floatchamber with sufficient force to spray outwards over the ignition tackle and also on to the sparking plugs. In the case of flooding there would naturally be some petrol draining down into the spray chamber and the air inlet, but this is dealt with by suitable drain pipes which carry the fuel clear of the engine and undershield. Furthermore this internal petrol accumulation could only be ignited by burning back from the engine and although the Bentley has more overlap than is usual with us when both exhaust and inlet valves are open together, we do not think that this is the source of the trouble as the air inlet system is well shut in and any emission of flame would be prevented by the gauze in the air intake, and should thus be unable to cause external ignition. We do not think the presence of the electric pump is the cause of any trouble as the function of this pump when switched on is to maintain the petrol at a given feed pressure which is sufficient for the flat out consumption. We can only say against it that if left on indefinitely it will pump out the complete contents of the fuel tank instead of the quantity being limited to a half gallon which would be the case with an autovac. We have therefore to look for some source of | ||