2RotorSpeed

iTrader: (1)

Since my last thread (https://www.rx7club.com/showthread.p...76#post6776376 ) about this was overun by bullshit, and nobody took it seriously, I will ask again:

I am trying to get my JDM S5 power steering to work with a S4 power steering control unit, in a car that came with the shitty engine speed power steering computer (89 GTU).

S4 power steering control unit diagram:


I have run wires from the stepping motor(6), through the firewall, and plugged into the control unit pins.

- 6 wires from stepping motor to pins M, K, L, J, P, N on the CU (control unit).
- From chassis ground to pin Q in the CU.
- From main ignition to pin O in the CU.
- From speed sensor(dash) to pin E on the CU.

Now, if we examin the wiring diagram we see some extra pins and are non-existant on the S5 models power steering control unit (which has only 7 pins):

- pin D on CU [which I assume has something to do with the A.A.S. (auto adjusting suspension)]
- pin R,A,C on CU goes to the A.A.S. control unit
- pin G on CU is a check connector (not sure what it is for, and it seems it doesnt go anywhere)

I have pins D,R,A,C, and G NOT connected to anything on the CU.

When I turn the ignition on, about 3 seconds later the CU starts to been and never stops... there is no breaks in the beep... it's a continuous been that never ends unti you turn ignition off.

Can anyone that knows what they are talking about please help with this?
Thank you.

NZConvertible

If you follow the wiring diagram through to the AAS page you'll see they actually go to the steering wheel angle sensor, which is used as an input for both systems. This sensor is critical to how the power steering system works, so you need to connect them up.

2RotorSpeed

iTrader: (1)

Ok, so pin R,A, and C on the CU need to be connected because they are from the 'turn cancel sensor). How about pin D and G? What is the 'coil with igniter' do anyways? or the check connector? Thanks

2RotorSpeed

iTrader: (1)

Also, what happens to the vehicle speed sensing power steering systems, when you removed the control unit out of the equation? Would you have something similar to the engine speed power steering? Or would the power steering not work at all (no assist)?

NZConvertible

Pin D goes to the coil tacho wire for an engine speed signal (follow the wiring diagram like I said) and pin G is the check connector (dunno what it's for, most likely diagnostics).

You'd have the same assistance as you do at idle, but it wouldn't reduce as speed increases.

2RotorSpeed

iTrader: (1)

Ok, found an interesteing problem. The wiring diagram for the S4 control unit is bad. We have checked it, and it is pins P and N that are used for power and not K and P. THat is WHY the S4 and S5 power steerings are interchangable. Other then that, anyone know what would be the consequence of not having the pin D conneced? Also, we have the thin pressure line plugged, because I still have the shitty steering rack with two lines... would that make the power steering not reduce fluid pressure at high speeds, or would it just be a little less efficient? Thanks again NZConveritble.

2RotorSpeed

iTrader: (1)

ok, so I got the pin D hooked up to the wire that goes to the tach since both have the same input from the ignition coil. I left pin G unconnected. Now I did not get a chance to drive the car because there was a short with the turn signal swich, and I'm not sure if it is related with the 3 pins that go to the turn cancel switch. I double checked everything, and it seems to be connected to the right place... UNLESS the s4 wiring diagram is bad again like it was with the previous two pins at the power steering control unit.

Also still would like to know what happens if I have the thin pressure line plugged, because I still have the shitty steering rack with two lines... would that make the power steering not reduce fluid pressure at high speeds, or would it just be a little less efficient?

Thanks.

NZConvertible

You mean not interchangeable...

The wiring diagrams clearly show the controllers are quite different and not swappable. The S4 one has 14 wires on a 9x2-pin connector and the S5 one has seven wires on a 4x2-pin connector. The S5's system appears to be quite a bit simplified, with no inputs for steering angle or engine speed.

The S4 controller needs to know engine speed to be able to correctly reduce assistance as speed increases, since the pump output pressure depends on engine speed and engine speed is not proportional to road speed through the whole speed range.

Oh dear... I assumed you'd already done this bit. There's no point in setting up the controller without the correct rack. You'll achieve absolutely nothing.

2RotorSpeed

iTrader: (1)

No, I mean the wiring schematic is wrong on the S4. I know the computers are different. I was not talking about that... but if you look at the wiring for the two control units and plugs to the stepping motor you will notice that the power steering pumps WOULD NOT be interchangeble between S4 and S5, which is FALSE since it's proven that the two pump are indeed interchangable! Pin P and N are the two pins that give power to the stepping motor, and not pin K and P as shown in the wiring diagram. This was tested by checking the voltage coming out of the S4 computer while ingition was on: Pin P and N give out 10.5 volts, while the other 4 pins(M,K,L,J) do not.

Anyways, I have finally wired the S4 computer properly (no more beeps ). I know I need the better rack but until I get one to replace this shitty one... I just wanted to have some power steering to make drifting less of a pain.

The reason why I DID not just put in the shitty power steering back into my car is:

- I never had it to begin with when I bought my rx7 off a friend.
- I heard the VSSPS was much better for racing and drifting (which is what I use my car for)
- I already had an S5 Tii pump since it came with my JDM engine when I did the swap

Thanks for the help again tho.

PS. So the thiner pressure line is the return line on the vehicle speed sensing power steering pumps? which relieves pressure in the system to compensate for higher vehicle speeds... and the thick pressure line is just a pressure line.

NZConvertible

I can't see it working that well for drifting. Wheelspin will make the computer think you're going much faster than you really are and reduce assistance.

I believe so. If you want to learn more download the Steering chapter of the 86 Training Manual (link in FAQ). There's a very extensive description of how the system works in there. It's not for the faint of heart though...

2RotorSpeed

iTrader: (1)

Cool, thanks so much for your help NZConvertible. I'm about the try out this power steering this weened (w/o computer) and see how that work out for drifting. Then once I replace the rack I will be able to see how the VSSPS feels for gripping/drifting. And, if I somehow I don't like how the VSSPS deals with the pressure change for drifting, then I'll just unplug the control unit at the track. =)