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I am trying to reduce the pressure of my power steering system. I could use some help

Posted by yoshimitsuspeed, Nov 1, 2004
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  1. yoshimitsuspeed

    yoshimitsuspeed Proven Member

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    portland, Oregon
    Okay I know this is long, I am hoping just long enough to screen out people with ADD but interesting enough to catch the attention of people who could give me some good input.

    I am trying to reduce the pressure in my power steering pump as well as it's force to the wheels to somewhere between 25 and 45% of it's current strength.
    I am also thinking I may want to modify the restrictor which cuts off flow at high rpms so that under 2000 it is a little stronger for parking lot manuevers and such but over 2000 gets a little stiffer but from there maintains an even restriction. I am thinking this may be possible by elongating the holes on the sides or increasing the diameter of the middle hole and adjusting the spring pressure.

    Since the restrictor restricts flow more than pressure I would also like to lower the pressure to increase feedback and reduce steering force to the wheels while going straight and big wide open corners.

    I wanted to upload a photo to make my questions clearer and easier to understand.
    My first one (I know I should have a real manual but I could barely afford the new line that started this endevor) I was wondering if anybody has a detailed schematic of the pump.

    My second question would be easier to answer with my picture (I will try to upload it again later). If you remove the apperatus that has the restrictor in it there is something else that is simalar underneath it. It is pushed up by a spring and sits up against the restrictor.
    I don't understand how this could be the pressure bypass but it is the only thing in the pump that even looks like it could be the bypass, Unless the pressure bypass isn't in the pump. If this is the bypass putting a softer spring in would lower the overall pressure in the system right? If this is not the bypass where is it, and would putting a softer spring in work?

    My third question is for the restrictor that is usually disabled altogether.
    I am guessing there is a notch that under low pressure the four holes line up with and are able to flow fluid through. As pressure increases the holes must be pushed past the notch.
    I am thinking that if you put a spring in that compressed around 2000 rmp and elongated one, two, or three of the holes downward then once it hit 2000 rpms or so is would be restritcting the flow as much as it can so it won't get worse at high RPMs.
    Or I could use a softer spring and bore out the middle hole a little to get better flow when it is completly closed. Any sugestions which way to go?
    This experiment is taking place on a spare pump so if I mess things up I won't be too sad.
     
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  2. Tevenor

    Tevenor Proven Member

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    Why?
     
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  3. yoshimitsuspeed

    yoshimitsuspeed Proven Member

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    Well here's the story. One of my power steering lines busted so I took off the line and the power steering belt so I could drive it around for a couple days till I get the new line.
    Of course in parking lots and trying to quickly turn the wheel having no power steeing sucks but when I was going fairly straight and especially when I got it out on the open road I realized how much feedback I had been missing. It was also easier to hold smoother more fluid lines through corners due to some back pressure on the wheel.
    I don't want to change to a manual rack because I don't want to (I don't know how gear ratios apply to steering racks but I am going to say reduce the ratio)? :confused:
    Any ways I want to keep the asisted ratio.
    So my thought is if I get the power steering just strong enough to be able to freely move the wheel I should be able to reduce it enough to get better feedback, feel of the road, and smooth stability at high speeds.
     
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  4. giester2

    giester2 Proven Member

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    I don't know if this information will help you or not but here I go:

    1. The power steering pump must have a minimum of 1000psi and 2.5 gpm of flow (during a turning manuever) for you to have any power assist. Most pumps put out 1200-1400 psi and 3-4 gpm flow. Pump pressure at idle without turning the steering wheel can be much lower.

    2. The gear assembly (rack & pinion) tells the pump how much pressure to supply. The pump will only put out the amount pressure that it is told to. If a manuever only requires 1000 psi, the pump will only put out 1000 psi even if the pumps maximum pressure is 1500 psi. This occurs because the pumps main mission in life is to overcome restrictions in the system. As the control valve in the rack is turned, ports open and close (depending on which way you are turning) creating restrictions in the flow of fluid. The pump senses this restriction and ups the pressure to try and overcome it.

    3. In most variable assist steering systems, engineers mainly focus on decreasing the flow rate of the system. Reduction of the flow rate at high speeds will reduce the amount of power assist that you have (if need be I can give examples). Most of these systems are controlled by several components (evo or solenoid, speed sensor, and steering wheel positioning sensor) and a computer (some systems have their own brain for the ps, others are controlled by the cars brain).

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    And remember the front suspension of a vehicle directly effects the power steering system

    example : My mom and I have the same car (Pontiac Grand Am SE V6). They have the exact same pump and the exact same rack & pinion. My mom's car feels like it has super cadillac power steering, while mine feels firm and tight (when you drive my mom's car and then drive mine, mine almost feels like it doesn't have power steering). The only difference in these two cars are the rims and the tires. My car's tire are wider and have a lower profile (smaller sidewall) then my mom's car.

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    I hope this helps a little. And by the way, I have seen many people try to lower the pressure in their pump to reduce the amount of assist, and I have never seen it work to the customer's satisfaction.
     
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  5. yoshimitsuspeed

    yoshimitsuspeed Proven Member

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    Thanks for the help. I was assuming the power steering system was a little simpler.
    Your post got me to check out howstuffworks for the basic tutorial. I still have a lot to learn before I know what I am talking about on the subject but I don't understand why there is a min gpm and psi but I guess it doesn't really matter since it seems the lower the pressure, the more force on the torsion bar untill the you reach max flow so it wouldn't be progressive and wouldn't have an effect untill there was a good deal of fprce applied. At least that's the way I understand it.
    evo or solenoid, speed sensor, and steering wheel positioning sensor
    ^^^ Do these replace the torsion bar on more modern vehicles or are they in addition to?

    Now this sucks because the way they explain it there is no P/S force exerted when you are going straight which is good but you still want feedback from the road but as soon as the road gives feedback force is applied to the torsion bar before the wheel theoreticly completly neutralizing feedback before it reaches the wheel.
    I love feedback. As a former CRX owner I learned a lot about driving from the feedback through the wheel. I also like my wheel being a little less touchy. Is there any way to do this without going with a manual rack?
    What about a softer torsion bar?
    Is this possible? Would it work?
     
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  6. giester2

    giester2 Proven Member

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    I am glad you looked up more information on it. A softer (or thinner) torsion bar will give you lighter steering. Think of the torsion bar like spring. The easier it is to twist the easier your steering will be. We will sometimes "turn down" the torsion bar (shave some metal off) for elderly and disabled people to make it easier to turn the vehicle. So on the opposite side, the thicker and sronger the torsion bar is the firmer the steering will feel (sometimes its called effort).
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    your quote:

    "I don't understand why there is a min gpm and psi "

    The minimum level is only considered during a turning manuever. Going straight down the road, the pump barely puts anything out, but when you start to turn you need a minimum in order to overcome the forces.
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    your quote:

    "evo or solenoid, speed sensor, and steering wheel positioning sensor
    ^^^ Do these replace the torsion bar on more modern vehicles or are
    they in addition to?"

    These are in addition to the power steering system. At this time every passenger vehicle on the road that has hydraulic power steering has to have a torsion bar in the gear assembly. The solenoids and sensors only monitor the system and make settle changes to affect the steering.
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    If you would like to learn more about power steering and variable assist, I can email you some docs put out by the major car companies for their mechanics and docs put out by steering manufacturers (there are only about 6-7 companies in the world that design power steering for vehicles).

    As a suggestion, I would study how the angles on the front end of a vehicle affect the steering feel. I think you may be surprised how much you can adjust. Even changing the bushings on the front end can make the steering feel firmer (it makes the steering exert more force to get the tires to move).

    Any way let me know if you want the info.
     
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  7. yoshimitsuspeed

    yoshimitsuspeed Proven Member

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    Yeah I would appreciate the info. Thanks a lot for your help. I am guessing it would be a bit of work to make a firmer torsion bar.
    I will PM you my email.
     
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