Power Steering Pump

Servopump

Pump for power steering – high power   Art.no: Unic 392X-03
(Used for Rallycross Supercar and other cars where a high power level is needed)
— Deplacement: 6.5 cm3/rev.
— Oil pressure: Normally 100 -140 Bar  (base setting of pressure reliefe valve = 100 Bar) Higher pressure then 140 Bar can be achived with changed valve spring  (the pump is dimensioned for 250 Bar).
— Pulley for Multi belt PK-6. Outer diameter Ø132 (measured outside of belt grooves).
— Connections: Thread R 3/8″ female in both in & out ports.
— Filter unit with interchangeably filter. Connections 2x AN 8.
Additional technical info:
— Recommended outer diameter of the crankshaft pulley = Ø93 ± 5% (measured outside of belt grooves) = ratio 1.42. Too high rev. can damage the pump. The pulley should be adapted for Multirem PK-6 or PK-5.
— Recommended hose dimensions:
Pressure line between pump and steering rack = Ø6mm.
Return from steering rack to tank through filter unit = Ø8mm (filter must be used).
Feeder line between tank and pump = min Ø10mm (also through the connectors).
— Recommended tank volume: 0.5 liter  min.
— Oil cooler is normally not necessary due to the high efficiency of the pump.
— The setting of the pressure relief valve can be changed if needed. The pressure level is dependent on factors such as the piston area in the steering rack, the ratio between the steering rack and wheel (length of the control arms…) , caster angle and  while also other suspension geometry influences but although not as much.
— Pump efficiency coefficient:  mechanic 0,9  ,  volymetric 0,9
— Torque on the pump shaft at 100 bar = 6.5 x 100 / 20 / 3.14 / 0.9 = 11,5 Nm.
— Used power at 100 bar and engine speed 6000 RPM = 11,5 x 6000 / 9550 / 1.42 = 5,1
kW (ie peaks that occur during cornering).
— The average power consumption at fullspeed on track (supercar) = approx. 2.2 kW (based on average pressure of 50 Bar and engine rev.5000 rpm). When the car is in full acceleration the pressure is usually low (<15 bar) and therefore the pump uses low power (< 1 kW).

 

– Keep in mind that a bad pump “steals” more power even if the servo effect is worse. The poorer efficiency coefficient as standard pumps (vane pumps) have at high pressure levels makes the oil warmer and thinner, and thus the efficiency is even lower, i.e. a vicious circle. Hot oil increases wear and also the risk of rupture of hoses and seals.