Progessive/speed sensitive steering modification?

MN12Racing

Registered User
If I'm not mistaken, my 91 is equipped with this...? Is there a nice long read anywhere about how this system works?
If I have it, I'd like to disable it, and keep it locked on the low-speed setting. I.E. most steering movement for the least hand work.
Any idea how do do this? This is a fairly alien system to me, where are the sensors that tell the car how fast your going? I'd imagine if I just unhooked them, the car would think itself sitting still.
 
The speed sensor is in the transmission tail section on the drivers side but if you disconnect that then the speedometer and odometer won't work. The sensor for the power steering is on the side of the pump. It's called the EVO sensor but I believe that it defaults to less effort rather than more effort if disconnected. I don't think it changes to fewer or more turns lock to lock, just to more or less effort to turn the wheel.
 
On our car, which has a shock control system, the shock control module also controls a electronic controlled orifice valve mounted to the discharge port of the power steering pump. This based on the various inputs that the shock control module tracks, including steering wheel angle and road speed.

When disconnected, the valve is all the way open, providing maximum assist. This site seems to have info you might be able to use to generate a false signal to close the valve.
http://www.aa1car.com/library/2004/bf10434.htm


With Programmable Ride Control

PURPOSE
The Variable Assist Power Steering (VAPS) System controls power assist, which depends upon vehicle speed and steering wheel angle. The Automatic Shock Control Module provides a large amount of assist when the steering wheel angular velocity is high, at low speed and when parking, for example. A smaller amount of assist is provided at high speeds to allow greater road feel.

OPERATION
With the Ignition Switch in "RUN", voltage is applied to the Steering Sensor and to the Automatic Shock Control Module.

The Power Steering Actuator, which is controlled by the Automatic Shock Control Module, controls a hydraulic valve, which determines the amount of hydraulic assist available to the driver.
 
If I'm not mistaken, my 91 is equipped with this...? Is there a nice long read anywhere about how this system works?
If I have it, I'd like to disable it, and keep it locked on the low-speed setting. I.E. most steering movement for the least hand work.
Any idea how do do this? This is a fairly alien system to me, where are the sensors that tell the car how fast your going? I'd imagine if I just unhooked them, the car would think itself sitting still.

Can I ask you why you would like to do this? Stiffer steering wheel at speeds give you more control by not allowing you to jurk around the steering wheel.
 
Can I ask you why you would like to do this? Stiffer steering wheel at speeds give you more control by not allowing you to jurk around the steering wheel.

I road race the car, so first of all I want consistent steering. Secondly, I want sharper steering and better response at all speeds, so I want Max assist at all times. I don't "jerk" the wheel around, you're not fast unless you're smooth, so I'm not worried about that. :)

Many thanks for the replies guys, especially that link, Mike!
Eric
 
The ratio of the rack and pinion gear is fixed. The EVO system only varies the amount of assist you get at various speeds. The faster you (up to a point anyway) the less power assist there is so you have better road feel. I have no idea why you would want max. assist ALL the time. Most people want less assist which is why some of the Mustang Boys use a second orifice in the system to further restrict the fluid flow (and assist) at the rack and pinion steering gear.

Whatever you do do NOT disconnect the VSS. It also provides speed info to the EEC to tell it what idle speed should be (electronic dashpot) and sends a signal to the Cruise Control too. I guess you could disconnect the connector to the EVO Valve on the PS Pump if you are insistent that max. assist is what you want.
 
If this will be only for racing, there are pure manual racks that you can install in there.

Usually in racing you want less assist, not more, as more assist removes feedback from the steering wheel that you could otherwise get.

I've heard of 2 racks so far where the owner initially complained of sudden loss of power assist, or sudden increase in power assist when going around a corner or making a turn. Turned out to be something wrong in the steering rack.
 
I suffered some sticking of servo valve in the steering rack causing variations in power assist. I flushed the steering system with new fluid and the problem cleared. Followed the Ford Shop Manual procedure....worked. I did unhook the low pressure return line and it IS important to keep adding fluid as you flush or you will suck in a lot of air into the system.
 
From what you're all saying, How would I go about locking it in minimum assist? At the very least, I could try each one out.

If this will be only for racing, there are pure manual racks that you can install in there.
Yes please. :)
What racks will work? I wasn't aware that it was an option on these tanks?
 
I road race the car, so first of all I want consistent steering. Secondly, I want sharper steering and better response at all speeds, so I want Max assist at all times. I don't "jerk" the wheel around, you're not fast unless you're smooth, so I'm not worried about that. :)

Many thanks for the replies guys, especially that link, Mike!
Eric

Then you sure don't want max assist, there is no feedback through the wheel that way. Have you driven the car at different tracks with various corner speeds? Are you uncomfortable with the way the steering feels?

FWIW, I've run mine on half a dozen different road courses, the variable steering has never caused a problem. Generally it will be bleeding off most or all of the assist once your up to speed on most corners at the track, in my experience.


cheers
Ed N.
 
Then you sure don't want max assist, there is no feedback through the wheel that way. Have you driven the car at different tracks with various corner speeds? Are you uncomfortable with the way the steering feels?
A bit actually, but that may be a metter of the old rubber bushings. The front of the car will be adressed over the winter.
I'm basicaly hoping to remove what I see to be an uneccesary system from the car. A manual rack is even more appealing, because it loses the PS pump. The only problem I've seen on the tracks with my MN12s has been boiling of the PS fluid.
This car may make it into the NASA time trials series in 2009, I'm not at all concerned about comfort or retention of factory components.

I recognize your name, you've been around here a while, I only stop by occasionally. :) I have some questions about your caliper brakets, I've PM'd you.
 
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There is a user with the name TIM that you could PM. he should be able to tell you the details of the rack he used. I believe it was picked up from autozone so it was a standard rack.
 
The manual R&P is a direct fit just use your tie rod ends from the old one, you also need to remove the bottom section of your rag joint by drilling out the two rivets then use the bottom section from the new rack use some bolts & tak weld the nuts...simple mod.;) Im gonna build a steering shaft so Im using a u joint from flaming rivers since the shaft will be thinner.
rack & pinion.jpg u- joint.jpg
The place is called Antioch auto parts 847 395-3660 ask for mike sexton & tell him that Tim Keiss sent ya!:cool:
OMAR
 
The manual R&P is a direct fit just use your tie rod ends from the old one, you also need to remove the bottom section of your rag joint by drilling out the two rivets then use the bottom section from the new rack use some bolts & tak weld the nuts...simple mod.;) Im gonna build a steering shaft so Im using a u joint from flaming rivers since the shaft will be thinner.
View attachment 29250 View attachment 29251
The place is called Antioch auto parts 847 395-3660 ask for mike sexton & tell him that Tim Keiss sent ya!:cool:
OMAR
Very nice! What car did that RnP come from?? Mustang? Iw ould want a faster tratio rack, not a slower one.
If the mustang manual rack fits, wont the power rack? If this is the case, that's one more bit of mustang aftermarket that I can get in on. A tight manual rack would be fine on the track, but hell in the paddock with big tires.
Edit:
http://www.jegs.com/webapp/wcs/stores/servlet/product_10001_10002_761783_-1_10441
15:1 for the same price. ;)
 
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Why not just step up to the higher ratio rack and ditch the PS system giving you more power to the pavement?

The rack that Tim used I believe was a pinto setup. If you use the AJE or Flaming River setup, those guys make you use thier inner and outer tie-rod ends causing you to drop quite a bit of extra coin.

The steering assist setup also has a reluctor wheel on the steering column. If you tilt the wheel down, you will see it in there. It also give the pcm the signal for the ARC. The faster you move that, the ARC will come on and it will add/take away the PS pressure.

Chris
 
The sensor wheel in the steering column is used to input steering angle to the EEC/PCM. With angle plus VSS (speed) signal the EEC/PCM calculates lateral acceleration (g force) and switches the ARC as needed.
 
Why not just step up to the higher ratio rack and ditch the PS system giving you more power to the pavement?

I've considered this. The trouble is:
-I already have enough power to get me into trouble. :) I'd want a manual rack for the reduced complexity and weight.
-I'll be road racing, averaging a 1/2 hour drive at a time, with potential for a 24hr race. Manual steering would be tolerable, but it would wear on me faster.
-The Paddock. I'll have 245 wide race slicks on the front wheels, I'd like to not need an impact wrench to turn the steering wheel in the pits. :)

If you use the AJE or Flaming River setup, those guys make you use thier inner and outer tie-rod ends causing you to drop quite a bit of extra coin.
I've seen this, but may consider it acceptable. My question; what is the difference between Mustang and MN12 Tie rod ends? Would they work?
 
Trust me ... you will want to have power steering for a 24 hour race ... I've done 2 of them. ;)


cheers
Ed N.
 
Dredging up an old thread here. I'm wondering about the ability to remove the variable steering component altogether by installing a pump made without it. I am looking to simplify my car and one of the things I dislike is this variable steering system.

Would this work? If I bought a pump without the VSS?
 
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