Speed Sensitive Steering - What Controls It?

[bubba]

Trying to figure out what controls the speed sensitive steering in my R32 for a couple of reasons..

First being that I would like to turn it off for track days (could just pull the plug from the HICAS computer I guess).

Secondly, I would like my Stagea to have the same sort of speed sensitive steering.. definitely needs to be heavier at high speed.

Is it purely electronically controlled? or is there special valving or something involved?

/discuss

[some_cs_student]

Pretty sure its the HICAS computer, check the tutorial on removing hicas, it mentions not disconnecting the ECU for a reason on an R33, I *think* its the same for an R32 but best to check...

[predator]

On r32 for speed sentivity - valve .. controlled by ECU, based on speedo.

Disconnecting the plug is not going to do much, other than let the toe in of the rear wheels vibrate around which will not give you any benefit. To do it properly you need to lock the rack.

Rear swaybar and locked rack makes a good difference - very predictable.

[bubba]

Where is that valve located? pump or rack? would there be a way to set this up in the Stagea?

Already got a lockbar along with swaybars and coilovers etc in the 32, HICAS computer is still plugged in. Would pulling the plug on the HICAS computer immediately turn the steering hard? I guess if it's controlled by the HICAS computer and that is removed then it should instantly become heavy..

[nisskid]

what do u mean take it out for track, u mean the HICAS or the speed sensitive front steering?

there is a speed sensitive control, pretty sure it works off the speedo cable, im pretty sure there are 2 stages, full power steering, and just power assist. personally i think any proper circuit work feels like shit with only power assist, having only power assist for highway driving is good as not much turning is needed, so the wheel is firm and doesnt want to move a lot, but when ur trying to move it a lot like at the track it feels like shit.

a manual rack is one thing, a powered rack without powersteering is another, atm i have an issue where i can only get power assist at all speeds (due to not having a speedo) and especially for drift it feels like shit, yes its harder to turn, but not in a good way, the rack is very sluggish unlike a manual rack, it provides fark all feedback and just doesnt feel very responsive at all.

this probably has nothing to do with what ur talking about, but yeh.

[bubba]

I'm talking about the speed sensitive steering for the front..

My understanding was that it is progressive from ~60km/h - ~100km/h.

Anyway, the MAIN reason for this topic, is to try to understand what controls the speed sensitive steering and whether it could be adapted to another car..

[_Ryan_]

my stag felt a little better once i added adjustable camber/castor bushes and wound in max castor

[heller44]

Basically, on a 32 anyways, you have the mechanical speedo drive to the dash cluster. Then from the cluster you get a pulsed output relative to speed (frequency changes not duty cycle) that is transmitted to the hicas / ps module in the boot. This then works out what is meant to happen and outputs a signal to the solenoid on the power steering rack (front of car) that changes the hydraulic assist effort. This signal is fixed frequency but varying duty cycle.

I understand with 33 and 34's it is the same, just no hicas hydraulics, but power steer assis is still hydraulic solenoid, same same.

To transfer the lot into another vehicle you would need some sort of module to replicate this completely and having a speed input available, using a hicas ecu wouldn't work cos it will fault with not seeing the the correct responses from the hicas, wheel sensors, steering wheel angle sensor. As well as using a rack with the solenoid on it.

I have thought about making a unit up to remove the hicas ecu and just do the steering assist but haven't been arsed yet. Got my hicas / power steering all working before I made it that far.

If any of that made sense, well..

James.

*edit ps, definately progressive, I have a graph here from the gtr workshop manual, and a couple of cro photos from when I was discussing this with SK a long time ago..

Edited April 25, 2009 by heller44

[bubba]

my stag felt a little better once i added adjustable camber/castor bushes and wound in max castor

My stag handles really well, it's just the steering at high speed is too light for my liking..

Heller, cheers I was thinking something like a variable resistor on the wire going to the rack solenoid but now that you say it's varying frequencies that controls would probably need something like a pulse width modulator? (I'm not an electronics guy )

[heller44]

Does the stag have variable assist at all?

One thing you could do for track use with the 32 is shove a switch in line with the rack solenoid, open the circuit. My car was like this for over a year cos the git that wired everything up forgot to wire the rack in, along with the clutch switch, reverse light, speed signal, etc etc... was quite driveable, even carpark speeds weren't a problem, if you climb under the car, and look from the back of the rack forward, you will see the solenoid where the steering column mates up. Just unplug it there and test..

The unit I was thinking of making would just take a speed input and generate the solenoid drive.. Letting you lock out the hicas without a fault and being able to adjust the gain of the steering to how you wanted it.. Reasonably simple circuitry just haven't found time effort motivation..

[260DET]

Interesting topic, does the solenoid operate a variable volume valve to regulate the amount of oil flow? In other words, what mechanical device regulates the amount of power steering? And in what way does the solenoid operate that mechanical device?

[bubba]

Does the stag have variable assist at all?

One thing you could do for track use with the 32 is shove a switch in line with the rack solenoid, open the circuit. My car was like this for over a year cos the git that wired everything up forgot to wire the rack in, along with the clutch switch, reverse light, speed signal, etc etc... was quite driveable, even carpark speeds weren't a problem, if you climb under the car, and look from the back of the rack forward, you will see the solenoid where the steering column mates up. Just unplug it there and test..

The unit I was thinking of making would just take a speed input and generate the solenoid drive.. Letting you lock out the hicas without a fault and being able to adjust the gain of the steering to how you wanted it.. Reasonably simple circuitry just haven't found time effort motivation..

Is the solenoid you are referring to the big HICAS solenoid thing under the intake manifold? if so, I removed that when I removed all of the associated HICAS gadgetry. All that is left is the HICAS computer in the boot..

I like your thinking with the circuitry, I'm not sure if the Stagea has variable assist but even if it didn't, could a signal be intercepted or modified at all?

[heller44]

The solenoid is built into the steering rack itself, where the steering column meets the horizontal part of the rack the solenoid is like a large wart on the intersection, two wires coming out of it to a two pin inline connector to a harness that dissapears up into the nethers of the car.. You might be able to see easier than me, the 26 and its attendant bits fills the engine bay that well my monkey mitts can't follow..

If there is no solenoid on the stag, you would have to insert something like a bypass valve in the hydraulic loop to reduce the assist. Not something I would be playing with. Have a look and see, I would be suprised if it doesn't have it since it is basically a 'line anyway.

One way to alter the solenoid drive signal is to use something like the jaycar kit, digital pulse adjuster.. takes a duty cycle input and modifies it for the output.. Seem to remember an autospeed artical using this kit for adjusting the steering response on a lexus or something a while back.

James.

[bubba]

Excellent work James, I will report back when I have investigated a little further!

Engine is coming out of the 32 soon so will look at the rack and splice in a switch. Will also attempt to look at the rack in the Stag.. not sure if I'll be able to see anything past the diff/driveshaft/etc.

[heller44]

Put the car up on ramps, slide in under the drivers side floorpan and look forward at the rack. It is very obvious what you are looking at when you get there.

Try unplugging the solenoid before you go to the trouble of a switch.. You might not like it.