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POWER ASSISTED STEERING FOR MGS WHAT, WHY AND HOW!

Do you love everything about your MG except the heavy steering? If you’re not as young as you used to be, do you find steering difficult? If so, why not consider fitting power steering?
The conversion is engineered and designed to reduce effort and stress while enhancing the dynamic response. By using modern components, these mechanical-hydraulic systems eliminate unwanted mid-corner steering shocks. Whilst low-speed manoeuvres or parking is made almost effortless. As it is mechanical-hydraulic, the power steering system gives a much better ‘feel’. Your everyday car has power steering, so why not your classic car?

Introduction

PAS systems have advanced considerably over the years. Design experience and modern machining have made the pinion valve in the rack more precise. Falling rate pumps (the faster they turn, the less they power) have added sophistication of feel versus assistance. Exceptional driving and handling cars of the past- Porsche 911, Porsche Boxter, Lotus Excel and Lotus Elan M100, all had Hydraulic Powered Steering. Aston Martin fit a hydraulic system to all their new model cars and Mercedes in their new E-Class cars. For real driving enjoyment, choose Hydraulic! Hydraulic power-assisted steering has serious advantages over other systems when fitted to classic cars. It will tell the driver exactly what’s happening on the front wheels, giving involvement, better steering feel, reward, and is the type of steering fitted to the car in the era made. Electric Power Steering systems don’t provide the same level of feedback and detail as hydraulic systems because instead of responding to a force, they respond to movement.

MGOC Spares MG Classic Modern Parts Accessories V8 Supersport MGB Roadster
Power Steering Pump & Reservior In Situ

​The electric motor worm gear turns a gear either attached to the column or one that meshes directly with the rack, leaving the direct link from the steering wheel broken. The connection between your force turning the steering wheel with the assistance is gone, hence the lack of road feel. When retrofitted to classic cars, it still uses the existing steering rack, so any wear and backlash in the original rack remains. EPS, when fitted, is on the drivers-side footwell, where British classic sports cars, such as the MGB, lack space. Thus, taking up what little spare room there is, squashing legs and knees, which would be hazardous in the event of an accident and could compromise comfort in everyday driving.

Main System components

  • A reservoir containing the power steering fluid
  • The power steering pump is driven by a belt from the engine
  • The steering rack with a valve head and an assister ram

How power steering works

Hydraulic Power Assisted Steering is a demand-based system that uses a spring-loaded servo valve (Valve Head) to sense the application of torque to a pinion shaft. Proportionally directing hydraulic pressure against a piston connected to the steering rack to overcome the effort of turning the steering wheel. The entire system is full of fluid (both sides of the piston, all the hoses and passages within the servo). With the pump

running fluid flows from the reservoir, through the valve head, and back to the tank.

How the steering rack valve-head works 

During rotation of the steering wheel, the servo valve opens in direct proportion to the degree of twist applied: if a twist exists to the left, for example, fluid (provided by the pump) will flow to assist a left turn. With more twist the valve will open up more, resulting in a higher rate flow until sufficient pressure builds (against the piston in the cylinder) to overcome the resistance. If the twist is released (or resistance is overcome, which amounts to the same thing), the valve springs back to its central position where all fluid is permitted to exhaust. In actual operation, pressure builds up and overcomes resistance within milliseconds. The “twisting” of the input shaft, the “catching up” of the output shaft and the release of tension occurs. For all practical purposes, simultaneously and continuously. The weight of the steering can be altered by making the spring-loading of the valve stronger or weaker, accomplished by making the torsion bar thinner or thicker.

The Pump

The hydraulic power, or more correctly hydraulic pressure, is provided by a rotary vane pump driven by the engine. The pump contains retractable vanes that sit in a stator and turn within an oval chamber. As the vanes spin, they pull hydraulic fluid from the reservoir and pump it to the Valve Head under pressure. The pressure generated then acts on the piston in the ram. Pressure and flow are the two factors that give the steering its lightness/weight and feel. The pump must provide an adequate supply of pressurised fluid at low engine revs, so the steering has good assistance levels at parking speed but not too much-pressurised fluid at high engine revs; to moderate this and make the modern pump efficient, pressure and flow valves are fitted. A pressure relief valve is fitted to limit the pressure applied to the assister ram at full lock, which can also be used as a part of the steering feel calibration.

A flow control valve stops the pump from producing too much fluid as its revs rise in tune with the engine revs. However, there is more to it than that. The valve body, the housing, the ports and the control spring are all used to give sufficient flow for the maximum power assistance to be built up. Also incorporated is the ‘falling rate’ characteristic. Meaning that as the pump speed rises, it produces less fluid output. The assumption is that mechanical pumps are inefficient and take a lot of power to drive them. Not true. When cruising in a straight line, it is taking about one half of a horsepower, when turning corners about one horsepower. Which is less than the effect of low tyre pressures or a headwind let alone enthusiastic driving!

Fitting Power Steering to your MG

Kits are available for all MGB, MGC, V8 and RV8 Models and are suitable for DIY fitment and specialist workshops. Comprehensive illustrated instructions detailing installation are available on request via e-mail or post. For those and any further technical advice, we are here to answer any of your questions- Call us on: 01954 230928.
On all but the MGC kits, the front cross members are modified to take new steering rack mounting brackets that are welded into place using a jig provided. Readily modified cross members are available for those not wishing to undertake this, but the rest of the installation is completely “bolt-on”.

Invitation to Test Drive

If you are interested in Power Steering for your MG and would like to book a test drive, telephone MGOC Spares on 01954 230928 to arrange your appointment
Test Drive

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