TAZ-NZ

How integrated into the cars other systems is the controller for electric assist power steering ?

The reason I ask is I'm trying to work out if it would be feasible of transplant the power assist steering rack for an RX-8 into an 3rd Gen RX-7. The electric assist system is a huge improvement in my eyes over the hydraulic power steering system in the RX-7. It only draws power during corning, it has to weigh a whole lot less than the hydraulic pump, motor, pipes & fluid put together, and it also helps clean up the engine in a big way.

While I realise this wouldn't be a straight forward swap, there are sure to be some issues with the mounting of the steering rake, and if it would come into conflict withe RX-7's sub-frame or 13B's sump.

But the main issue I can see with this swap is the control system for the power assist itself, I know it's tapped into the RX-8's fly by wire throttle system, which allows it to vary the power assist depending on the speed of the car, etc. But how integrated into these system is it ? Is the controller build in the steering rack itself, or is in some little box hidden away in the dash, or is it part of some other system, making it impossible to separate ?

I'm sure if the power steering assist controller can be separated from the RX-8s other system, that you could find a way to substitute the extra inputs required form the throttle etc on the RX-7.

I've used the forum search function and can't find any information on this subject, if I've missed any other threads on this topic, please feel free to point me in the right direction with a link.

Speed Racer

I don't have the service manual in front of me but I'd be willing to bet that all of the control signals are passed directly to the ECU through the CAN buss. So to get it to work you'd probably need to use the RX-8 ECU and a bunch of its sensors to keep it happy. IMHO that sounds like more effort that what it would be worth.

Go48

Based on the RX-8 tech CD, the Electronic Power Steering (EPS) system consists of the:

EPS Control Module located under the PCM (ECU)
Ball Screw
EPS Motor
Steering Gear & Linkage
Steering Rack & Pinion
Torque Sensor

The EPS Control Module receives signals from the Torque Sensor as well as vehicle and engine speed from the PCM, and adjusts the current to the EPS motor based on driving conditions. That ought to give you some idea of the complexity involved in adapting the EPS system to your RX-7. IMO, Speed Racer is right on the mark as far as the "cost-benefit" of such a mod, if in fact it is even doable. But hey, maybe you're willing to tackle it anyway. In which case I wish you the best.