Sorry... here is the relevant information. Maybe we can have the same done for the NSX. This is for the 91-95 MR2 with power steering rack.
They use an electro-hydraulic system, which is quite different than the 2K or NSX.
My recent ownership of an s2k gave me an appreciation for a tighter ratio. It took me many miles of city driving to get used to the loose ratio of the NSX.
I too would like to see a tighter replacement similar to that of the s2k (2.4 turns lock to lock as opposed to NSX 3.07). BTW s2k is elec power assist.
I agree with OP, for track use that has a lot of hairpins, a quicker steering ratio would greatly help.
The point of the thread was to figure out how to make a quicker steering ratio for the NSX, not whether it was a good idea/for everyone or not...
Practically I don't think it is going to happen. A higher ratio on the street means more driver input to negotiate low speed turns or parking lots. On the track in a 180 degree hair pin as well, sure. Seems like a minor issue.
I'd like electronic cockpit EPS adjustment and perhaps a tighter CART inspired ratio too. :wink:
However, assuming maintaining assist and other stock characteristics is a priority.... I suspect from what little I've read in the service guide that people will need to deal with what Honda gave us in the NSX PS department. If you study the service guide you'll realize how involved the stock PS system is. While I haven't delved in too deep, I highly doubt it is as simple as changing out a pinion or gear for the later model EPS racks.
While usually it is just that simple, the electronics for the EPS assist likely complicates the issue greatly in this instance. To expand on that...
For starters yes, the steering shaft drives a fixed pinion which we could use to machine a replacement. However, note that it is also connected to a series of transmission gears, and then to a rotation and torque sensor which simply converts the speed and direction of steering input into voltage signals, which is then sent to an interface circuit and then on to the control box.
The control box software then calculates the duty signals from the cars speed sensor, torque sensor, and steering rotation sensor and outputs electronic signals to the power unit which then drives the rotor, which mechanically drives a ball screw, which transfers motion to the re-circulating ball screw, which provides the assist you feel on the rack when engaged.
So, my first premise would that assuming you changed the steering ratio with an alternate pinion, the assist benefit of the PS would be totally out of wack as it would be expecting different input, and some way would need to be devised to compensate electronically which would take some R&D. Otherwise, as the PS would cycle through the various control modes (Normal, Return, and Damper) it would be doing so using the wrong input position for each of the duty cycles.
There is an adjustment rack guide screw which helps to see the pre-load, but it wouldn't solve the root signal issue.
I am also skeptical that even given the change-over was successful, that over the long haul the over-voltage cut-out would operate normally and not burn out the motor unless something was devised there. Otherwise you might hit the end of lock, and the motor may still try to provide assist.
Ultimately, it comes down to this. Has anyone cracked open an NA2 power steering assembly yet and really delved in on steering tech? I haven't seen anything on 2K boards either with these style of units. It seems to be hands-off.
I noted in the service manual it emphasizes to not service, disassemble, or otherwise screw with it as it is a 'higher precision' and to always replace as a unit.
However, I suppose doing the completely opposite couldn't hurt either. :smile:
