www.RX7fb.com

I’ve bought a factory power steering setup for a 1st gen.... here’s a bit of a write up on how it works and the parts involved....

The 1st generation RX7 came with 3 different steering boxes.... a manual box fitted to the series 1&2 cars, a different ratio steering box fitted to the series 3 cars and a power steering option using yet another ratio in a power assisted box.

The s1 / s2 box was a faster steering box but heavier to steer.... easier to adjust and tends to stay in adjustment better.
The s3 box was slower but lighter to use.... more comfortable with wider 205 tyres but tends to go out of adjustment easier and is temperamental to adjust.
The power steering box is hydraulic assisted, faster and stays in adjustment better than the s3 manual box.

The power assisted steering was, as far as I’m aware, only available on US spec GSL / GSL-SE models (only available in left hand drive) and the Japanese domestic market GTX which was RHD.

1st gen factory power steering is speed sensitive power assist giving less assistance at higher speeds and more assistance at lower speeds.
1st gens with PAS were vehicle speed sensitive, 2nd gens were engine speed sensitive and for the 3rd gen, Mazda went back to vehicle speed sensitive.
The system comprises of the steering box, pump, reservoir, control valve, lines central processing unit and speed sensor.



The PAS steering box differs from the manual boxes in that the steering column itself, although in 1 piece on the manual boxes, is a 2 piece setup with a coupler where the column passes through the bulkhead.... very handy if you were doing a FC subframe swap.





The steering box also obviously incorporates the hydraulics and has a high pressure ingoing line (from the PAS pump) and a low pressure return line (back to the pump).







These lines are fed through a separate control valve...



which is itself controlled by the CPU...



on information received from the speed sensor...



As the vehicles speed increases the CPU opens the control valve to bleed off some of the fluid pressure and thus reduce the amount of power assistance. A separate electronically controlled valve on the pump stops all PAS above 55mph.
It is a simple but effective system. The reduction in PAS is proportional to the vehicles increase in speed..... as the speed increases, the PAS reduces until 55mph is reached and the PAS stops......
As the vehicle slows, the PAS is increased. Without the electronics connected, the PAS would operate at maximum assistance at all speeds.

The CPU is located under the dash, just above the steering column and below the instrument cluster. The speed sensor is built into the speedo in the instrument cluster.
The steering box is a straight swap for the manual box and uses the same mounting point / bolts. The control valve mounts to the front offside chassis rail just ahead of the front suspension turret. The hydraulic lines then pass across the engine bay, bolting to the front engine mount and then connect to the power steering pump. The lines are routed this way on RHD cars to provide cooling to them from the airflow at the front of the car. On LHD cars where the lines are shorter, a separate cooling loop is included.

The pump itself is mounted on a strong iron bracket mounted to the 4 studs on the side of the engine, just below the distributor. These studs are usually redundant on UK spec cars



There are 2 types of bracket ( aircon and non-aircon) My bracket is the aircon bracket which will also mount an aircon compressor.

As said, as far as I’m aware, the RHD power steering setup was only available for the Japanese domestic market. When the opportunity arose to buy a system from a JDM car, I thought it would be a good thing to have. 1st gen PAS in RHD is incredibly rare.... I've never seen another one in the UK.
The donor car was the JDM 12 turbo GTX being broken by Tool. We stripped the system off together and when removed, it was still full of bright red power steering fluid and looked to be in excellent condition. Before using it however, I will probably change the seals in the pump and maybe the steering box just to be on the safe side.

The wiring proved a bit of a challenge to work out. The JDM car had the PAS wiring incorporated into the loom and the correct connectors but UK cars have different wiring looms. ..... suss’ed it out in the end.

The CPU has 5 wires coming out of it:

1. Control Valve (out)
2. Pump pressure switch (out)
3. Speed sensor (in)
4. Earth
5. Ignition





The speed sensor is built into the speedo and connects via one of the main plugs on the back of the cluster.

I haven’t yet decided which car to fit this setup to.... my black Elford or the ex-3 spires series 3. I’m looking forward to using it though.

at least the parts are going to good use, i have seen fc frames put into an fb.

how do they work with the speed sensing, the whole steering column is from the fc?
you could use the parts and make your black fb into a jdm? if the shell was too bad to repair off the original
then might as well do some organ donation into a better shell. it was a shame it couldn't be put back on the road
but then you wouldn't have got these parts.

it'll be interesting to see how you get on and if they'll all go together again and work properly.

spoddy wrote:at least the parts are going to good use, i have seen fc frames put into an fb.

how do they work with the speed sensing, the whole steering column is from the fc?.

no.... it's all explained in the post.

spoddy wrote:you could use the parts and make your black fb into a jdm? if the shell was too bad to repair off the original
then might as well do some organ donation into a better shell. it was a shame it couldn't be put back on the road
but then you wouldn't have got these parts. .

I don't want a JMD copy... just a few of the options that we never had over here.

spoddy wrote:it'll be interesting to see how you get on and if they'll all go together again and work properly.

it'll all go together again and work properly... no worries

Nice write up Ian.

Strangely though - I've not connected any plugs on my FC PS setup and it appears to operate at zero assistance rather than the other way around.

It would also be interesting to know if the upper section is actually long enough to reach to the FC rack though, if so it certainly would make the conversion much easier and it wouldn't matter lhd or rhd column.

Still, I'm sure if that were the case someone would have figured it out? Unless you have just stumbled onto something??

If my caster bushes really pull the wheels back as they should and the ps column fits a treat then we have opened up a world of easy Fc subframe conversions

fair enough, i was just wondering how bringing the fc pas into an fb would be different any easier.
how heavy is the steering in an fb, say compared to a mk3 fiesta, last car i had with no pas.

RamoNZ wrote:Nice write up Ian.

Strangely though - I've not connected any plugs on my FC PS setup and it appears to operate at zero assistance rather than the other way around.

It would also be interesting to know if the upper section is actually long enough to reach to the FC rack though, if so it certainly would make the conversion much easier and it wouldn't matter lhd or rhd column.

Still, I'm sure if that were the case someone would have figured it out? Unless you have just stumbled onto something??

If my caster bushes really pull the wheels back as they should and the ps column fits a treat then we have opened up a world of easy Fc subframe conversions

the coupler is inside this housing... just inside the bulkhead...



I think it would simplify a fc conversion.... you could retain the top half of the steering column and all the fittings etc and wouldn't need to disturb anything within the car ......but would maybe need to get a section of shaft made up with a uj to link from the coupler to the fc rack...

spoddy wrote:fair enough, i was just wondering how bringing the fc pas into an fb would be different any easier.
how heavy is the steering in an fb, say compared to a mk3 fiesta, last car i had with no pas.

Very heavy indeed at standstill spod. No weight at all once you are at road speeds. I would think the Fiesta would be a lot lighter?

My missus was a Primary Teacher....the FB's her car, was a daily drive. She's a very tiny built lady but the kids took one look at her biceps and knuckled down to their work.

codge wrote:

spoddy wrote:fair enough, i was just wondering how bringing the fc pas into an fb would be different any easier.
how heavy is the steering in an fb, say compared to a mk3 fiesta, last car i had with no pas.

Very heavy indeed at standstill spod. No weight at all once you are at road speeds. I would think the Fiesta would be a lot lighter?

My missus was a Primary Teacher....the FB's her car, was a daily drive. She's a very tiny built lady but the kids took one look at her biceps and knuckled down to their work.

you wanna try turning an rx8 steering with no power, or when the electric rack goes out.
been a good number of years since i drove a car with no pas, was just curious, closest was when my mx3 disty gave up and got towed home.
i'd love a drive in an fb to see what they're like steering wise.

i've heard of aftermarket electric assisted steering being put into some old cars, nothing like that can be done to the fb, if you cannot
get the original pas steering?

spoddy wrote:you wanna try turning an rx8 steering with no power, or when the electric rack goes out.

I can cheer you up by saying that driving a none-power assisted steering car (eg. and FB) is much better / nothing like driving an "assisted" car with the assistance gone!

I presume the actual leverage ratio must be different when they know it is going to be assisted.

I