924Board.org

[IanJ]

For those that don't checkout the 924S discussions can you please take a look at this.... http://www.924board.org/viewtopic.php?t=11329
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It's only funny until someone gets hurt.....then it's hilarious!

[leadfoot]

I've heard of an alternative for swapping out the power steering to use a resistor in series with the positive supply. This drops the voltage and allows less assisistance.
I forget where i saw this done, it may not even be appropriate, but what they did do was wire in a different values through a switch so they could vary the setting of assistance.
Another way of varying output voltage would be to wire in a voltage regulator to change voltage output. Some electronics supply stores like jaycar sell kits like these.
Leadfoot

[gohim]

leadfoot,

Some later model cars use separate electrically powered pumps to vary the steering effort. This pump is not the normal belt driven power steering pump.

An example of this would be the 96 and later Ford Taurus and Lincoln. Earlier model cars without OBDII emissions control systems are less like to have variable rate power steering controlled by the ignition/emissions control brain.

On the Ford Taurus, the PCM (computer) uses an electrical signal from a sensor on the transmission called the VSS (vehicle speed sensor) to decide how to set the steering effort. The VSS is prone to failure, and when it drops off, the PCM immediately cuts off the voltage to the electrical pump (the PCM thinks the car is parked when it does not receive a signal from the VSS telling the PCM that the car is moving), and the car suddenly has manual steering.

The 924S does not have variable rate steering, or the electrical pump that would go with it, so there is no "changing the resistor to change the steering effort".

[924RACR]

Even fancier, the cars that I work on (like the '04 Pontiac GP Comp G with Bosch ESP) have what GM calls Magnasteer II (or MSVA = Magnetic Steering Variable Assist). This is a variable steer assist on top of normal hydraulic power steering. It varies the steer assist based on (as I recall) vehicle speed and lateral G's (since both are measured). Pretty groovy.
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[leadfoot]

gohim,
Are there any advantages to having hydraulic operation, why did porsche install these systems over electric??
leadfoot

[gohim]

May be you didn't understand what I was trying to explain to you. The electical pump portion of the power steering in the late model Ford Taurus is used only to operate the variable rate portion of the power steering system. I suspect that it does not take that much electrical power to control, or operate the electrical pump, wold react faster, and is easier to manipulate than if a second mechanical power steering pump was attached to the front of the engine.

In truth, my feeling is that the 924S does not even need power steering, since I haven drive a 924 without power steering since 1981. Still, the weight distribution of the 924S is more towards the front, and the 924S does weigh more than the 924, and some people did whine about the steering effort required to park the 924.