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Discussion Starter #1 (Edited)
I'm getting ready to convert my NA6 to manual steering (no power-assist) so I thought I'd share some resources that may be helpful to others considering to do the same. You basically have two options: install a manual rack and pinion steering gearbox from a base model car or you can de-power your power-assisted rack and pinion steering gearbox.

There are several ways to de-power your power-assisted steering gearbox. One way is if your steering pump fails or if you simply remove the drive belt from the pump. This is the least desirable approach because you'll be manually pumping fluid through tiny orifices which creates friction, significantly increased steering wheel input effort, and reduced road feel.

Another method is to simply drain the fluid and then "loop the lines." This means you re-route the power steering lines so that air is simply pumped from one side of the steering gearbox to the other. According to Andrew Coe, begin by draining the P/S fluid from the rack by disconnecting the return line (the one w/ the banjo fitting) and crank the steering wheel from lock-to-lock until fluid stops coming out (takes about 15-20 times). This will leave a small amount of residual fluid if you are concerned about lubrication. Next, disconnect the metal section of the return pipe w/ the banjo from the hose that runs back to the reservoir. The hose is held on w/ a spring clamp but your car might be slightly different depending on the exact model year. Cut off the pressure hose (make sure you leave it long enough to wrap around to the other side), slip it over the end of the return pipe and hose clamp it. This "loop the lines" method is okay, but there is still a considerable amount of friction due to the main seal inside the steering rack.

The best, albeit most involved method, to de-power your rack and pinion steering gearbox is to fully disassemble it and remove the internal seals.

If your car has high-mileage you may also consider replacing the inner and/or outer tie rod ends, the rack and pinion mounting bushings, and possibly even installing inner tie rod end spacers to give you more steering angle. An upgrade to 93LE/R-package tie rod ends may also be beneficial, especially if you have a lower than stock ride height.

Here is some basic info about power-assist steering systems common on modern automobiles like our beloved Miata:
Woodward Machine Corp. Technical Reference Section
Woodward Machine Corp. Power Steering System Tech - HTML
How Car Steering Works by HowStuffWorks.com

Here is a tutorial on swapping a power-assisted steering gearbox for a manual rack and pinion setup.
projects: Swapping Miata Power Steering @ Werkz.com

Here are some tutorials on how to de-power your existing power-assist rack and pinion steering gearbox
De-Powering the Power Steering Rack @ teamfc3s.org
Conversion to Manual Steering @ Miata.net
How to "depower" a Miata steering rack @ FlyinMiata.com

If you de-power your rack and pinion steering gearbox by totally removing the internal seals and removing the hydraulic fluid lines it is good to somehow block off the holes to keep foreign debris out. Here are some places that sell metric plugs to block off the holes where the hydraulic fluid lines used to be connected.
Advanced Autosports
Metric Drain Plugs from CG Enterprises
MiataRoadster.com Black Anodized Plugs

The larger plugs are M16x1.5 but I don't know the length nor the size(s) for the other plugs. Some argue against plugging up the steering gearbox too tight. They instead prefer to connect the supply and return hoses together to avoid excessive pressure building up inside the steering gearbox as the wheel is turned from one side to the other.

If you want ditch your power-assisted steering pump but keep your air conditioning then you'll need to purchase a special idler pulley and bracket assembly (OEM Mazda p/n is BP01-15-930) so that you can properly tension the belt. If you get rid of both the power steering and the air conditioning then you don't have to worry about that drive belt whatsoever.

The NA manual steering gearbox has a slightly slower steering ratio (18:1) than the NA power-assisted steering gearbox (15:1). The NB Mazdaspeed Miata has a slightly different ratio but I don't know exactly what it is. I know it is allegedly a little bit quicker than the regular power-assisted steering gearbox and has slightly less travel, presumably due to the 17" wheels. So the NA manual steering gearbox has a steering ratio of 18:1 with 3.3 turns lock to lock. This means that one complete revolution (360 degrees) of the steering wheel results in the wheels of the car turning 20 degrees (360 divided by 20) or 18:1. Note that this measurement is car dependent and may be different if you install the same steering gearbox in a different car with different suspension geometry. Because of that, many aftermarket steering racks are listed with a steering rack ratio that is calculated differently. For instance, a Woodward steering gearbox with a steering ratio of 2:1 means that for one complete revolution of the pinion the steering rack will move 2 inches.

Woodward Machine Corp. said:
The ?ratio? of a rack and pinion is the distance the rack moves in one turn of the pinion. In the car this linear motion is translated back into rotary motion at the steering arm. The overall steering ratio of the automobile, then, is the ratio of input (in degrees) at the pinion or steering wheel, to output (in degrees) at the steering arm or front wheel. For example, if one turn of the steering wheel produces 20 degrees of turning angle, the steering ratio is
360:20, or 18:1. The length of the steering arm influences the steering ratio as much as the rack does. The shorter the steering arm, the greater the turning angle for a given linear movement, and, consequently, the quicker the steering. A given overall ratio can be arrived at using either the combination of a short (quick) arm with a small (slow) pinion, or the combination of a long (slow) arm with a large (quick) pinion. If a choice is possible within the design envelope of the car, the latter combination is the mechanically superior. A guide to steering ratios appears elsewhere in the technical reference section, but, very generally, the most common rack ratio for road racing is 2 inches per turn, for pavement oval track racing 2-1/2, and for dirt oval track racing 3-1/2 to 4.
So, in summary:

NA manual rack = 18:1
NA power rack = 15:1
NB power rack = ??
NB Mazdaspeeed Miata power rack = ??
 

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Discussion Starter #2
Flyin' Miata sells Superpro polyurethane bushings for the steering gearbox mounts.

Flyin' Miata said:
Superpro steering rack bushings

Your steering rack is attached to the subframe with a couple of rubber bushings. Of course, this rubber is now at least a decade old. These polyurethane mounts will provide a more solid mounting for your rack, improving steering accuracy and feel.

Fit 1990-97 cars only. The power rack version can be installed easily, but the manual version requires the removal of one tie rod.
 

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bad mother f......
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Thanks for the Info. I plan on doing this mod while my engine is out next time.

looks like the retail for the idler pulley that is required with air conditioning is $132.65.
 

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i did this mod when my motor was out, and i loveeee it. infact opon driving my car, my two friends with ae86's immediately depowered their steering racks. i looped the lines and drained most of the fluid and packed the steering rack from the bottom with some grease fo extra luberacation. do it, you will love!
 

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bad mother f......
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I plan to just loop the lines. I dont see myself ever getting the rack back together If I rip into it.
 

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bad mother f......
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hate to double post, but I found a real Gem of a post on miata.net http://forum.miata.net/vb/showpost.php?p=1982564&postcount=13

Aparently, there is a kit, part number NA01-YV-SK1 that includes the pulley setup, the belt, and all the nessesary mounting bolts. It is also cheaper than buying the the pulley kit buy itself! retail right now is $88.06 compared to $132.65 for the pulley kit alone.
 

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I was going to say the pulley is about $99 from finish line. The rack is easy to take apart and reassemble. In fact it is harder to remove then it is to dis-assemble. All you need is some pliers to remove teh rings on the end, pull it out, cut off the bushing and reasemble. I just bent cut the lines and crimp the ends.
Dan
 

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The swap isn't hard...It took me and my cousin approx 3 hours to swap in an R package steering rack. Would've been done faster if the damn U-joint wasn't being a pain in the ass!

Anyway, my a/c is coming out next, so I have a spare pulley if anyone needs it.

PS- The manual rack rocks!
 

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i removed all the fluid from my rack and added grease to it along with plugging all the lines and it feels great to me.
 

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bad mother f......
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hate to double post, but I found a real Gem of a post on miata.net http://forum.miata.net/vb/showpost.php?p=1982564&postcount=13

Aparently, there is a kit, part number NA01-YV-SK1 that includes the pulley setup, the belt, and all the nessesary mounting bolts. It is also cheaper than buying the the pulley kit buy itself! retail right now is $88.06 compared to $132.65 for the pulley kit alone.

I just ordered the kit from Montomery Mazda and it was only $73. If your looking to do this and keep your A/C now may be the time to do it. They are impossible to find in the used market and are about $60 when you do.
 

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I am a member of the ignorant masses. Please enlighten this old fart as to the advantages of de powering the steering. Thanks
 

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better feel of the road for the front tires, weight reduction, simplifies engine bay, and maybe a teeny bit of hp increase.
 

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I am not trying to be a "smart ass" but do the front tires give you a truer or better translation as to when they are going to let loose without power steering ?OR is this a butt dyno reaction like getting more performance by adding a " cold air intake " or the 10hp gain by switching to a free flowing cat back muffler ?
 

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I`m really thinking of doing this, but I guess I`d try to find a used ps rack.
If I decide to sell the car in the future, the buyer would probably want powersteering.

Anyone know how much a used PS rack for a 01 miata would run?

-n
 

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bad mother f......
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bad news, the inexpensive "kit" (NA01-YV-SK1) has been obsoleted. You now have to buy the pulley (BP01-15-930), which is still available but $106, the belt $10, and use your old P/S pump bracket and bolts.

I have been looking for the part used for like 3 years to no avail, so I went a head got the pricer, still available parts.

NA parts are slowly, but surely becoming hard to find, this is just the beginning.
 

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So I've ran it plugged and open (breather filter). It is much more difficult when it is plugged as air is still fighting through to get from one side to the other (unless you did it FM-style)

Question though... this bracket lays behind the P/S pump. Is it okay to remove this completely like the bracket holding the A/C? Or must it stay in place? I woulda removed mine already but I can't get to one of the bolts. If it's anywhere as heavy as the AC bracket is, I'll remove it eventually.



 

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bad mother f......
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Yes you can remove it. 3 bolts I believe
 
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