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).
Cold start issues and experiments with air/fuel mixture devices on car engines.
| Identifier | ExFiles\Box 75\2\ scan0272 | |
| Date | 5th October 1921 guessed | |
| Oyl - G 51021 Sheet #2. To overcome this by a scheme as shown in the enclosed details, which allows us to play around with the size of the jet in order to get a rough setting of our mixture and to adjust the restriction on the air supply for the fine setting. The air supply restriction is adjusted by screwing the air pipe up or down. It is evident, however, after testing this device on four or five different cars under conditions of leaving the car out all night, etc. that there is too much restriction on the mixture, and the second device you sent us, which fastens on top of the induction pipe, therefore promises better. This device, however, failed to open up with the spring you sent with it, when we tried to start on a cold morning. With a soft spring made from a cut-down throttle spring the results achieved were better, though the mixture was weaker when the engine got running, the automatic air valve opened at slow speeds of the engine sufficient to give a firing mixture which would turn the engine around. Mr. Caswell, however, this morning with an air temperature of about 50° on a car that has stood out all night in air temperatures getting down towards freezing, could not get enough gas from the priming device to run the engine. It gave two or three weak explosions and then died out. Heating the pilot jet body with a resistance coil gave a start. Mr. Hulley has had a number of our cars standing out nights lately, and has found it practically impossible to start them either with the priming device or pilot jet, but has achieved a quick start by pouring boiling water on the induction pipe above the carburetter and flooding the carburetter without using the pilot jet or priming device. This makes us think that the ultimate solution of this trouble will be the application of heat electrically to the induction pipe plus a choker or else a pilot jet with the application of heat. When we did get a start with Mr. Caswell's car this morning, we got the boilers full of gasoline; that is to say, we had collected about 36 cu. ins. of gasoline. On immediately stopping the engine, we found the condition of the cylinders perfectly dry; that is to say, the cylinders had not got filled up with liquid fuel although the boilers were full. On again starting the engine and racing it to empty the boilers, these discharged a lot of rich mixture into the engine and the exhaust smoked copiously; but on again inspecting the cylinders after the boilers were empty, they were still found to be dry - that is to say, the rich mixture had passed into the cylinders in a sufficiently dry form to keep them from fouling. | ||