Valkyrie

I know the brochures say the base model S5's steering rack is a 17:1 ratio (lower is better), and that the turbo/GTUs is a 15:1, and that they both have LTLs of 2.7, but according to the FSM, they both have "infinite" ratios, and that that the base model rack has a tighter LTL than the turbo (2.7 versus 3.06 or something).

Can anyone confirm which is accurate, the brochure info or the FSM?

I REALLY don't like the slow steering ratio (if I have to pass the wheel to use all the grip my car has on a tight corner it's TOO SLOW) and if the Turbo has a tighter ratio, I'd think seriously about changing it out (and preferably getting the speed-sensing system if it's plug-and-play).

Also, I could have sworn RETed had modified the steering knuckles in order to get more steering angle, but IIRC you can also increase the quickness of the steering the same way. I would think maybe there'd be a way to make a bolt-on peice that relocates the knuckle, by drilling a whole in the knuckle, and putting two bolts in that hole, and in the original knuckle... although that's sort of a bandaid fix.

There are a few companies that make quick ratio racks for various cars (Most notably the Race Tek ones for Subarus, but they're EXPENSIVE...gives you a 13.5 or better ratio though), although some aren't for power steering (one company in the US even makes them for the AE86... only takes it down to a 2.5 LTL though), and I can't find any OEM-fit kits for the FC...

I can imagine it would be pretty costly to one-off machine a solid metal shaft with about a bajilion teeth, along with the gear needed to match it... probably upwards of two grand or more (hell it could be much worse)

Another way to increase steering is with a steering column that has a gear set in it... there's a company that makes them for Subarus and they work fairly well, apparently (cheaper than the racks but still expensive).

Or maybe maybe Miata racks of a certain year could be converted? Unless they're not any better than 15:1... Lancer Evolutions have a rack of about 13.5, so I've heard. STi's also have quick racks.

Valkyrie

Does anyone at least know if the S5 turbo and S4 power racks have a faster "feel" than the S5 GTU/GXL racks?

riverzendz

Considering that the S4 & S5 power racks are a lower ratio, then yes, they do feel faster than, say, the higher ratio the 90 GXL & GTU.

Specifying by series isn't accurate because that does not determine the ratio.

I prefer my S5 TII rack over any other one I've driven including manual and the 90 GTU rack. Faster, I'd say so.

micah

The NA S5's came standard with RPM sensing variable power assist.. and the turbo's came with vehicle-speed sending variable power assist.... I would imagine it would be easier than you think. Perhaps just changing where the sensor hooks up... or a control module. However, it COULD be a function of the ECU.. so might not be swappable.

Valkyrie

Well, according to the brochures, all the S4 power racks were 15.2:1... but according ot the FSM, the RPM-sensing (ie, base power steering for S5) actually has fewer turns lock-to-lock.

The question is which one of these sources is true (just like how the FSM says they both have the same front brake rotors whereas the brochure says the GTU has smaller ones...iirc they're the same).

But I could have sworn the GTUs was supposed to have the same rack as the T2 (speed-sensing, and 15.2:1).

riverzendz

My quote is from Black91n/a's thread in the archive about de-powering power steering. Giving credit where credit is due. Maybe you should PM him.

j9fd3s

iTrader: (3)

there are 3 steering racks for the FC

the manual, FB01-32-110F

the 86-92 "fast" rack, 15:1, FB78-32-110B

the 89-91 slow rack, 17:1, FC01-32-110

theres a big sticker right on top of the rack, you can see it if its not oily....

Icemark

The S5 cars switched every year. The 89 GTU had the crappy engine speed 17.4: 1 sensing steering which eventually phased into all non turbo models and the Infini models (it is lighter).

The Turbos without power steering had the 20:1 rack, while the turbos with power steering (vehicle speed sensing) had the 15.2:1 (or often call the 15:1) rack.

You have to look at the sale brochures for what S5 you want to know about, to find which S5 non turbo had which rack.

As far as the GTU brakes.. they followed the same changes. The 89 had smalller front brake rotors (but the same size pads) while the 90 had the larger brake rotors (but still the crappy single piston brakes). Mazda dealers typically replaced the 89 rotors with the 90+ rotors if they did any brake rotor work.

The GTUs model did not come with the Turbo's 15.2:1 rack.

j9fd3s

iTrader: (3)

the parts catalog is vauge about what 89-91 cars got which rack, and looking at actual cars hasnt been any more informative.

the parts catalog lists 2 front brake rotors for the fc

FB01-33-251 which is the s4 4 lug
and everything else FB05-33-251

Valkyrie

I tested it today and it's a bit over 3 turns LTL.

Icemark

That is because they disconntinuted the small (9.8") 5 lug vented front rotor that the 89 GTU had and replaced it with the 10.8 that all other 5 lug front brakes had.

Valkyrie

Well I'm gonna try to find an S4 or S5 turbo power rack locally (very unlikely... I checked one place over the phone and it was missing the rack) and if possible the speed-controlled pump and PS computer (also unlikely).

At worst I could probably salvage the manual rack off of the one 87 base I've taken parts off of and trade it for a 15:1 power rack...lol

I also plan on getting the S4 control arms with their replaceable ball joints (whether or not mine are bad).


For some reason my car also seems to have some hellacious bump steer for a power steering car (although it's not dangerously high)... and I was getting tossed around with by the wind coming home today. But I wonder what sort of bump steer or reaction to wind is considered acceptable?

At the very least I seriously need to replace my front control arm bushings and preferably get some stiffer springs (and a strut tower bar) because my steering feel at high speed leaves much to desire.

Icemark

All S4 models that had power steeering (regardless of Turbo or not) had the same 15.2:1 power steering rack as the 87-91 Turbo equipped with power steering.

Valkyrie

I know. I meant S4 power OR S5 turbo power steering.

Dak

My car has a red sticker on the rack with a big J the FB78 then under that in a silver section what looks like a serial# starting wit a 9. Is this the 15.2:1 rack? It is an '89 GTUs. My parts car whish is an '89 GXL auto has the same sticker but a different # in the silver part except it also starts wit 9. Are they both 15.2:1?It sounds like the GXL should be but the GTUs should not, but both have FB78 on the sticker. Both cars have the speed sensing power steering.

micah

Mine says "FC01" and some other numbers. :P

Valkyrie

Semi-update/bump.

I've been looking into how to do the speed-sensing steering conversion, and so far the parts I know are different are:

1. The rack, 2. the computer (plugs into same harness?), 3. the pump (has an extra connector, in different places, and also has more holes for hoses to plug in) and 3. the pressure line (or lines, rather... there are two compared to one).

I have a theory that the apparently hydraulic locking the cheapo racks have when you pass over the middle point after quickly changing direction doesn't effect the good power racks because of the extra hoses (lets pressure bleed off?).

Although I will probably go ahead and try bleeding the air out of my rack again to see if it makes a difference (I seriously doubt it... the lockup I feel is so strong I can't even muscle through it, which is something compressed air bubbles wouldn't normally do).

Another issue that comes into play for this installation is, where is the second connector for the pump on the S5 RPM-sensing car's power/body harness? I can only find one, and I think the only non-connected mystery connector in my engine bay (besides test connectors and things for stuff I don't have) that fits the description supposedly goes to A/C or something.

And more importantly, does the S5 NA's body harness have connectors for the electronically (speed) controlled steering computer's speedometer connection? Meaning, is the body harness the same thing between the S5 turbo and NA?

Also, are S4 powersteering components comptabile with the S5 turbo ones? Supposedly the pumps are slightly different, and one may or may not have more connectors than the other one. And of course, S4 wiring is a bit different as well.

BklynRX7

Wheres Roen? This is his specialty.


Anywho, so whats the ratio and ltl on the manual rack? Im going to go see which I have in the morning.

Valkyrie

20:1, 3.6 LTL.

Rather ridiculous IMO...

Although suddenly the pool of coolant under my car has become a slightly bigger issue...

Roen

iTrader: (2)

lol, I waiting to swap in a 15.2 rack into my car, though some that I have spoken to says that it makes the car darty at highway speeds. I can also imagine that in autocross, a depowered 15.2 would require a lot of strength to turn effectively. Gotta start hitting the gym!

groznyiv

iTrader: (1)

The 1989 convertible has the fast 15:2 rack with vehicle speed sensing power steering standard. They went to the cheaper engine speed sensing rack in 90-91.

David

Valkyrie

Can anyone tell me if the S5 turbo and GTU body harnesses are the same part #?

Also, I don't think the 15.2:1 rack would be any "twitchier" on the highway, since a lower ratio means it takes more effort to turn the wheel, which works both ways: meaning, it's (referring to the steering wheel) less effected by road conditions, and while the car will react more quickly to steering, it would be less prone to bump steer.

And really, a 15.2:1 rack is still pretty mild, it's not like it's a 360-degrees lock-to-lock formula car's wheel.

robtechfabrications

hmmm...might need to investigate picking up an s4 tII powersteering rack...this would pretty much bolt into my 91 na with ps right?

Valkyrie

No... you need a different pump and computer, but whether those are plug and play hasn't been confirmed.

That is, unless you already have speed-sensing PS (probably not).

Roen

iTrader: (2)

or unless you're planning on depowering your rack.