The empty running of a pump consists in the movement of the piston from the total release position up to the closure of the tank feeding hole. During this movement, the pressure in the braking circuit does not increase and, consequently, there will be no braking action. From the closure of the forward feeding hole (effective race), the pressure in the braking circuit will increase until it reaches the desired braking effect. The effective race of the pump piston (scheme on the next page) necessary to obtain a certain pressure in a certain circuit, will always be the same. Since through the adjustment of the empty running run, the hiking of the piston is changed before the closing of the power hole, it is clear that by fixing a certain total race (empty + effective) as a reference, differen.
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