What is Magnetic power assist steering?
01-04-2007, 07:37 PM
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What is Magnetic power assist steering?
GM says the C6 Vette has Speed Sensitive, Magnetic power assist steering. I understand the speed sensitive part, but what is the MAGNETIC part? The Steering rack looks the same as all I've seen. GM has no information that even mentions it no do any of the car review articles. Anyone?
01-04-2007, 08:03 PM
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This is probably more information than you wanted, but here it is 
GM MAGNASTEER
In 1996, a more sophisticated type of variable-assist power steering developed by Delphi Saginaw Steering Systems, named "Magnasteer," was introduced on: Buick Electra, Le Sabre, Park Avenue and Reatta; Cadillac Eldorado, Seville STS and DeVille Concours; Chevrolet Corvette; Oldsmobile Aurora; and Pontiac Bonneville. In 1997, Magnasteer became standard on all Cadillacs and has since been added to a wide range of other GM makes and models.
Unlike EVO power steering systems, Magnasteer does not use an orifice valve to reduce pressure to the steering gear. There’s no solenoid or stepper motor involved. Instead, Magnasteer uses magnets to assist or resist steering input.
The Magnasteer control valve assembly is mounted on the steering rack in the same location as a regular control valve assembly on an ordinary power rack. Inside the base of the Magnasteer unit is a large electromagnetic coil. Just above the coil is an inner and outer pole assembly with a permanent magnet in the center. Steering feel is varied by changing the strength and polarity of the magnets, which in turn, is controlled by changing the pulse width and direction of the current to the coil.
On 1996 and 1997 applications, Magnasteer has its own separate control module. But on 1998 and newer applications, the Electronic Brake Control Module (EBCM), which also oversees the operation of the anti-lock brake system, handles the Magnasteer control function.
On most applications, the only input the control electronics uses for Magnasteer is the vehicle speed sensor. At zero mph, a negative current of approximately two to three amps flows to the Magnasteer coil. This causes the magnets to repel each other, which in turn allows more deflection in the torsion bar inside the spool valve assembly. This increases fluid flow through the spool valve to the steering gear for maximum power assist when it is needed most.
As vehicle speed increases, current flow to the Magnasteer coil is gradually reduced. At about 45 mph, current flow to the coil hits zero and Magnasteer has no effect on the amount of power assist (which is determined only by the torsion bar and pump flow).
Above 45 mph, the direction of current to the coil is reversed and continues to gradually increase up to a maximum of about three amps at 75 to 85 mph. Reversing the polarity of the coil causes the magnets to attract each other, which has the effect of stiffening the torsion bar. This reduces the amount of deflection in the torsion bar that normally occurs when the wheels are steered and causes an increase in steering effort for better road feel and high-speed steering stability.
On some Magnasteer systems, such as that used in the Corvette, the Electronic Brake Traction Control Module (EBTCM) also looks at input from a steering wheel position sensor to determine if more or less steering assist is needed under certain driving conditions. The main purpose here is to reduce oversteer by reducing assist when excessive G-forces are detected.
Compared to conventional power steering systems, Magnasteer gives the driver a much broader range of power assist with a smooth transition from low to high speed. What’s more, the system can be recalibrated to modify steering feel using a Tech 2 or equivalent aftermarket scan tool. There are three settings: factory, firmer and less firm. Just follow the scan tool prompts and that’s all there is to it.
In 1998, a second generation "Magnasteer MAGe" system was introduced on some GM vehicles. This version of the system does not use a permanent magnet, but uses a redesigned electromagnet that has one pole mounted on the input shaft and the other on the pinion shaft.
At low speed, there is no current flow through the electromagnetic coil. The level of steering assist depends solely on the calibration (stiffness) of the torsion bar. As speed increases, current flow to the coil is gradually increased up to a maximum of several amps to decrease assist and increase steering effort. Magnasteer MAGe uses vehicle speed as its only input, so there are no changes in steering effort during sudden steering maneuvers.
GM MAGNASTEER
In 1996, a more sophisticated type of variable-assist power steering developed by Delphi Saginaw Steering Systems, named "Magnasteer," was introduced on: Buick Electra, Le Sabre, Park Avenue and Reatta; Cadillac Eldorado, Seville STS and DeVille Concours; Chevrolet Corvette; Oldsmobile Aurora; and Pontiac Bonneville. In 1997, Magnasteer became standard on all Cadillacs and has since been added to a wide range of other GM makes and models.
Unlike EVO power steering systems, Magnasteer does not use an orifice valve to reduce pressure to the steering gear. There’s no solenoid or stepper motor involved. Instead, Magnasteer uses magnets to assist or resist steering input.
The Magnasteer control valve assembly is mounted on the steering rack in the same location as a regular control valve assembly on an ordinary power rack. Inside the base of the Magnasteer unit is a large electromagnetic coil. Just above the coil is an inner and outer pole assembly with a permanent magnet in the center. Steering feel is varied by changing the strength and polarity of the magnets, which in turn, is controlled by changing the pulse width and direction of the current to the coil.
On 1996 and 1997 applications, Magnasteer has its own separate control module. But on 1998 and newer applications, the Electronic Brake Control Module (EBCM), which also oversees the operation of the anti-lock brake system, handles the Magnasteer control function.
On most applications, the only input the control electronics uses for Magnasteer is the vehicle speed sensor. At zero mph, a negative current of approximately two to three amps flows to the Magnasteer coil. This causes the magnets to repel each other, which in turn allows more deflection in the torsion bar inside the spool valve assembly. This increases fluid flow through the spool valve to the steering gear for maximum power assist when it is needed most.
As vehicle speed increases, current flow to the Magnasteer coil is gradually reduced. At about 45 mph, current flow to the coil hits zero and Magnasteer has no effect on the amount of power assist (which is determined only by the torsion bar and pump flow).
Above 45 mph, the direction of current to the coil is reversed and continues to gradually increase up to a maximum of about three amps at 75 to 85 mph. Reversing the polarity of the coil causes the magnets to attract each other, which has the effect of stiffening the torsion bar. This reduces the amount of deflection in the torsion bar that normally occurs when the wheels are steered and causes an increase in steering effort for better road feel and high-speed steering stability.
On some Magnasteer systems, such as that used in the Corvette, the Electronic Brake Traction Control Module (EBTCM) also looks at input from a steering wheel position sensor to determine if more or less steering assist is needed under certain driving conditions. The main purpose here is to reduce oversteer by reducing assist when excessive G-forces are detected.
Compared to conventional power steering systems, Magnasteer gives the driver a much broader range of power assist with a smooth transition from low to high speed. What’s more, the system can be recalibrated to modify steering feel using a Tech 2 or equivalent aftermarket scan tool. There are three settings: factory, firmer and less firm. Just follow the scan tool prompts and that’s all there is to it.
In 1998, a second generation "Magnasteer MAGe" system was introduced on some GM vehicles. This version of the system does not use a permanent magnet, but uses a redesigned electromagnet that has one pole mounted on the input shaft and the other on the pinion shaft.
At low speed, there is no current flow through the electromagnetic coil. The level of steering assist depends solely on the calibration (stiffness) of the torsion bar. As speed increases, current flow to the coil is gradually increased up to a maximum of several amps to decrease assist and increase steering effort. Magnasteer MAGe uses vehicle speed as its only input, so there are no changes in steering effort during sudden steering maneuvers.
01-04-2007, 08:44 PM
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good info
Thanks, that is great information! I was going to use a C6 rack in a Ferrari that I've implanted a LS2 engine, but with this info, I may reconsider since I wansn't planning on using that controller, only the ECM. Thanks a bunch, Bob
Now thats what I call an answer, good job!!!
