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TKART magazine Tech Focus | The Dell’Orto P34-PB2 fuel vacuum pump
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12 March 2017
The fuel pump ensures that the correct flow of mixture reaches the needle valve or float bowl carburettor from the tank.
Let’s discover the secrets and operation of one of the most popular pumps in karting: the Dell'Orto P34-PB2
The Dell'Orto pump uses two membranes to exploit the engine’s pulsating back pressure: when the engine draws in air, i.e. when the piston rises, a vacuum is created in the crankcase pump that raises the one-way delivery valve (made of fluorosilicone) via a metal connector and draws fuel from the tank to the suction chamber via the “IN” inlet connection. Subsequently, when the motor generates back pressure, i.e. when the piston drops and overpressure is created in the crankcase pump, the diaphragm pushes the fuel into the "delivery chamber" via a second one-way valve. The fuel travels through the “OUT” connection and towards the carburettor.
The operating frequency of the Dell'Orto pump reaches 10,000 pulses per minute and the flow rate can exceed 50 l/h. It is very compact in size, weighing only 100 g in total. The body of the pump is made of fibreglass reinforced plastic polymer (Ryton BR111), which ensures the proper structural rigidity together with the strength and permeability required to make it durable. The P34-PB2 can be mounted either horizontally or vertically and even fixed on elastic joints to absorb engine/chassis vibrations and thereby limit interference in its normal operation.
The "IN" and "OUT" labels indicate the nozzles that carry the fuel from the tank to the pump and from the pump into the carburettor. The third connection, made of aluminium, fits straight into the cover and is connected to the vacuum pump placed on the engine crankcase pump: the back pressure that makes the diaphragms function comes from here
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