How to: de-power your steering rack the right way(please read this whole thing and the link posted before trying this)

I HOLD NO RESPONSIBILITY FOR WHAT YOU DO TO YOUR CAR, SO IF YOU SCREW UP, HURT YOURSELF, DAMAGE SOMETHING, DON’T LIKE IT, OR WHATEVER ELSE, IT’S NOT MY FAULT.

This mod is for anyone who wants the improved steering feel of a manual rack without the slowness of the factory manual rack. It also gives you the benefit of never getting ahead of the power steering during hard driving (autocross). As an additional benefit, this will get rid of a fair bit of weight off the front left corner of the car and free up a lot of space in the engine compartment if you don’t have air conditioning (the a/c bracket bolts to the p/s bracket I think). Finally, in my view, the absolute best part of this is that it’ll help you improve on the weakest part of your car’s performance, the driver. For reference, the manual racks are all 20:1 whereas the power racks were available in a 17.4:1 and a 15.2:1 ratio. I WOULD NOT RECOMMEND THIS FOR THE 15.2:1 RATIO RACK. The steering effort would be too high to be liveable on the street. The 17.4:1 rack, which I have, will be perfectly liveable on the street though.

The cars that got the 17.4:1 ratio racks are as follows:
The 89-90 GTUs, 90-91 Infini, 91 Coupe, 90 GXL, 90 GTU, and the 90-91 Vert.

The cars that got the 15.2:1 ratio racks are as follows:
The 86-89 GXL, 86-87 Sport, 88-89 GTU, 86-87.5 Base, 87.5-88 SE, 86-87.5 Luxury, 87-91 US spec Turbo, and the 88-89 Vert that were equipped with power steering

Thanks to Icemark for supplying the above information in a different thread.

This mod took me about 4 or 5 hours of work to complete, so it’s not a trivial job.

First, you need to get the stuff off the car. I’d recommend getting the belt, pump (you can just cut off the wire going into the bottom of the pump), bracket and hoses off first (after draining the system). You’ll need to get the dust boot off the steering column u joint also. Then take the outer tie rods out of the steering knuckles and remove the front anti-roll bar. Then undo the bolts holding the rack clamps on and remove the rack. Once the rack is off, undo the inner tie rod dust boots and remove the inner tie rods. Once you are at this point you can follow the instructions on Flyin’ Miata’s site: http://flyinmiata.com/tech/depower.php?x=1

There are a few differences between the RX-7 rack and the Miata rack. First of all to get the retaining cover off the end of the rack, instead of punching the retaining ring out like for the Miata, simply rotate the cover counter clockwise to remove the retaining ring that holds it in, it’ll come out of the slot on the end of the rack (the cover has a groove in it that you can use to spin it). Secondly, there is no supporting barrel in the middle of the shaft (or at least it didn’t come out of mine). The rest of the procedure is exactly the same for a Miata and an RX-7.

Assembly is the reverse of disassembly. Be sure to properly torque all the bolts and make sure there is nothing loose. Do not tighten the adjusting cover very tightly; this will cause you to have much heavier steering. You want it to be just barely tight; the lock nut will keep it from coming loose.

I just recently did this mod after having seen it posted on Flyin’ Miata’s site in the winter and after reading a few reports from Miata owners on miata.net, but as far as I’m aware, mine was the first RX-7 to have this particular mod done to it.

Now for driving impressions: For reference I’ve got 225/45/17 Falken FK-451’s on 17”x8” wheels with a 32mm offset and the 17.4:1 rack with a stock steering wheel and energy suspension bushings. There is a decided increase in steering effort at low speeds (like when parking), but it’s manageable assuming you’re not a weakling. The steering is also quite a bit heavier under low speed hard cornering (up to about 35mph or so, it’s most pronounced below 20mph or so though), but that comes with the much-improved feel. The steering effort during normal driving varies from being no heavier, to being slightly heavier, except when parking. I’d say that this mod is perfectly liveable on the street. The feel is very much improved and now I can quite easily tell what the front tires are doing as the power steering isn’t acting as a buffer for all that feel and helping out so you can’t tell how hard the tires are working. All in all it’s a great mod as it strips weight off the corner that needs it most, gives better access to the engine on the driver’s side, gives better feel, removes a source of parasitic losses for the engine, simplifies the system making it more reliable, and is 100% free. I’d recommend this mod, but not to everyone, it takes a certain type of person to appreciate it.

 

Just one comment, I know you personally don't suggest this mod for people with 15.2:1 racks, but I have removed power steering with this rack ratio and I still daily drive my car on the street and to my college's parking lot. It took about 2-3 days to get used to and after that it wasn't a big deal, so long you aren't weak as hell. In fact it's given me more muscle in my lower arm driving like this

But after over a year of doing this, I don't even notice it anymore.

Good writeup also, and I like the pics from Flyin' Miata's site.

 

I have the same rack dub has, and its nothing too difficult. After first removing the
Ps it was a BIG difference. But I have had the car sitting for 3 years, and just recently I finished the motor, I love the way the feel is apposed to the PS. It turns really good.and the feel is great.

 

i thought i would chime in, great write up man

i'm definetly going to pick up a spare PS rack and try this out.

it should be noted that with the fluid seals removed steering effort should be reduced over just taking the PS pump and lines out, since you don't need to leave any fluid to push against in the rack at all.

this also has the advantaged of putting less stress on certain parts of the rack, so you don't have to worry as much about the rack failing...

 

copied to 2nd gen archive

 

If i just removed the pump and looped the lines will it be fine or do i need to do this?

Also just wanted to say that i am with the first two. I got a 89T2 and unless your just tiny then it aint to hard to steer. I was one handing it in a matter of days.

 

Well to each their own, you're welcome to try it, but I'd think that the extra effort might get to you if you do much city driving. It'll also take more muscle to drive the car hard and you will loose some precision by having to strong arm it that much more. Anyway, my experiance is with the 17.4:1, so I can't really say other than with speculation how bad it'd be with the faster rack. I did however see a road racer post that with the fast rack depowered that his race car took a lot of effort and that it really tired him out in a race. Anyway, for a strong guy in a street car it will likely be acceptabe, it just depends on your priorities and comfort level. I'll be autocrossing my car this Sunday, so I'll post afterwards how it was compared to with power steering, and give more thoughts on day to day driving with manual steering.

Crusader_9x: You can just remove the pump and loop the lines, but it's not ideal. To have the lowest effort you should do this, it doesn't take that much longer, and it'll be better in the long run. Also if you fully drain the rack you no longer have lubrication, so you should at least pull the shaft and grease it, but then you might as well go all the way. It's really just up to you.

 

The only time you'll have trouble with the steering is in idle with no movement. As soon as you start releasing the clutch and move a bit, the steering becomes effortless. Not to mention at high speeds when you only have to move a few degrees.

 

Well I autocrossed the car today and it was fabulous. The steering is barely heavier than with power steering (20% heavier maybe), there's no sudden unexpected changes in steering weight (like when you get ahead of the power steering), and the feeling is improved. After a while of daily driving you get used to the manual steering and it's not an issue, you just have to turn the wheel while mooving. I don't regret doing the conversion for a moment. It'll take a few days to get used to, but once that's happened, you'll be glad you did it.

 

I'm a weakling so i might have to pass this on up, and i have the 15.2:1 rack so

 

I am curious as to what PS you guys had before, they had two types Speed sensing and engine sensing. The speed sensing is the on with the problems, getting ahead of the steerring, flat spots, etc, etc.

I personally am a fan of PS, if most racecars use it then it must not be a luxury.

 

I was afraid I wouldn't like it for about the first 2 hours, then it became obvious how much better the feel was. I use two hands on the wheel at very low speeds, otherwise there is no drawback at all.

 

As far as I know the 91 NA has the rpm-sensitive PS, rather than the speed-sensitive PS. I know mine does. I HATE it on autocross days.

Thx for the info! Very timely for me too, as I was just thinking about doing a manual swap for just the reason of getting ahead of the PS pump at autocrosses.

 

UPDATE!

I've taken the 17.4:1 rack out and it's sitting in pieces in the garage waiting to get the pinion shaft welded up. I've swapped in a 15.2:1 rack with a welded pinion shaft and it's great. The steering is even more immediate and direct with the pinion shaft welded. Definetely worth the time and effort to go the extra mile and do that step (not that it was bad before).

The 17.4:1 pinion is actually slightly different than the 15.2:1 pinion, so I took a picture of it stripped down and cleaned up.

After more than 2 years of hard use the pinion gear looks perfect. No signs of wear from the extra load on it from the lack of power, no signs that the tosion spring in the pinion is anything but fine. So those who might wonder if these are potential weak points without the power assist you can rest easy. I'll get it welded up tomorrow and put it back together then I'll contemplate whether or not to keep it.

Here's a better, more complete writeup including the pinion welding and it's FC specific: http://forum.teamfc3s.org/showthread.php?t=54847

 

is the 15.2:1 rack (which was S4 only i believe?) a direct swap with the S5 17.4:1?
is it a direct swap if you want to use the S5 PS also?

 

ive yet to do this. great info though. i guess the HOBART is gonna get broken out again!!
ive only driven 1 car without power steering, a honDUH CRX and if the car was moving it wasnt bad at all. i cant see much of a difference with these cars.

 

S5 Turbos also came with 15.2:1 racks.

The faster racks use a vehicle speed sensing system where the 17.4:1 use engine speed sensing.
I'm not sure what changes would have to be made (or if it's even possible) to convert from one to the other.
The racks are physically identical and will interchange but the pumps are different.

 

ok, thanks. yeah the pump is the issue i guess then. i know for a fact that the 2 different pumps have a different amount of lines so i assume the rack itself would have different fittings for each type of pump...
i don't really have a problem with the PS, but at autocross i would like a shorter ratio rack. i've driven a newer Subaru and I really like it just because the steering is very quick due to a lower ratio rack.

anyways, i don't mean to sidetrack this thread.

 

The racks are not physically identical. The 15.2 rack has three ports around the pinion, the 17.4 has only 2. The computers would be different to so while I'm sure it is possible, there would be a fair amount of researching the FSM's and the wiring diagrams side by side to see what needs to be done to properly change it. Peronally though I would prefer the speed sensing over the RPM sensing but in reality I think I'm going to like the 15.2 manual the best.

Black91N/A - thanks for the compliments & link.

 

i think a de-powered 15.2 rack may be a little too much effort on slower sections on autocross courses, especially if you are running big wide R-compounds.

 

I have a de-powered 15.2 rack with big 18" tires. It takes a little effort to turn the wheel when pulling out of a parking spot but after that its great. Feels really nice.

 

If you ignore the power steering connectors and are only concerned with swapping from one manual converted rack to the other, they're the same. It bolts right in with no issues.

 

That's what I meant when I said the racks were "identical".

The 17.4:1 rack actually has the boss for the third hose that the 15.2 uses, it's just not drilled/tapped.

 

So I have a 15.2 rack, is this something where I can just take the belt off the P/S to see what its like before I commit to de-powering the whole rack?

 

Not really.
There are still seals and fluid in the rack that will make the steering seem heavier than after a proper depower.