The Vaporizing Of Paraffin for High-Speed Motors
(Electric Ignition Type)

93 ROAD CAR AND TRACTOR MOTORS. in accordance with the density of the two fuels, the construction and arrangement of the carburettor, and in some degree by the compression; also again, to the manner in wliich the motor is handled and the woik it has to perform. Many of the London cabs and omnibuses are run on a paraffin-petrol mixture, the motoi being. usually fitted with a small petrol tank connected with a spring-closed snifting valve on the intake manifold or the carburettor, so that a whiff of unmixed petrol can be admitted just before pulling over the starting handle, which is supplemented by an occasional whiff for the first minute or two when starting cold ; also, in order to facilitate the operation, the snif ting valve is connected up within reach of the driver when at the front end of the car. In the opinion of the writer a double-feed system is preferable to the metliod described of using a mixed fuel of paraffin and petrol, as with a bi-fuel car- burettor carefully regulated, not only can the piopoition of heavy oil to lighit oil b© inereaseel to one in tlnee,. but starting and running throttled clown, be made moie reliable. The petrol and paraffin supplies, according to this system, are carriecl in separate tanks and fed to a specially constructed carburettor having independently controlled spray nozzles ; such carburettors, known as “ bi-fuel/’ may be either arranged with a hot-air intake, or be provided with a jacketed manifold as shown in Fig. 69 ; or again, be fitted with a separate vaporizer as shown in Figs. 70 and 71, the latter construction enabling the two fuels to be used in about equal pro- portions ; a separate vaporizing attachment can, of course, be used with either form of carburettor.