According to a jap mag i have read the standard suspension on the 300zx is adjustable, hard and soft, and the way of changin it between settings is by usin...and wait 4it....the handbrake!! ive got the service maual for the zx and seems 2b true as the hanbrake cable is connected 2 'rear shock absorber actuators' which somehow can change the stiffness of the shocks. now what the jap mag or my service manual dont tell me is how to change the damn things, ie switch between both settings. This is prob new 2most of u as nissan seemed 2keep this quiet 4sum reason. neway..

 

Does anyone know how to change between the hard/soft settings ??

 

:confused:

This has come up a few times on here.....try a search on 'handbrake' and it will come up with quite a bit I reckon.

The Z has ajustable rear dampers for anti-squat purposes...

 

I.E. when you are at full throttle, the rear dampers stiffen to prevent squat.

 

The test to see if this system is working is to lift the handbrake off it's rest, but not enough to cause drag. This should stiffen rear dampers.

 

HTH.

 

Robert.

According to the wiring diag , there is no connection to the ECU. http://300zx-twinturbo.com/cgi-bin/manual.cgi page RA-26

 

The Adjustable Shock Absorber Control Unit is connected to the rear shock actuators, the ignition switch, the parking brake switch, the brake warning lamp and earth.

 

How does it get the signal to firm up when the throttle is open? Or anything else come to that?

 

:confused: - Gio

right, ive bin trawlin thru the past postings on this site n ive found the answer, if the handbrake is clicked on one notch, so the light comes on on the dash, the rear suspension will stiffen up, seems a daft way of doin it but there ya r, thats japs 4ya!! nothins eva straight 4ward. the US models apparently have a button to do the same thing. next time i go out in the old 300zx i think i'll give it a blast n see what the difference is.

 

learn somethin new every day huh:D

Like Gio, I also looked for the control circuit that stiffened up the back on full throttle or high speed and it doesnt look like there is anything. If there was it would put on the handbrake light unless there's a diode in the circuit. Easy enough to make it switchable if you want it.

 

Its a bit of a mystery why Europe cars are done like this. Yet Nissan gives the handbrake light on as the diagnostic for checking that your rear shocks go stiff and back to normal when you put the handbrake down again.

 

Worth trying the handbrake light on if you go on a track day and see how it handles.

Originally posted by WillieO

Its a bit of a mystery why Europe cars are done like this. Yet Nissan gives the handbrake light on as the diagnostic for checking that your rear shocks go stiff and back to normal when you put the handbrake down again.

 

Worth trying the handbrake light on if you go on a track day and see how it handles.

Yes when you click up one click on the handbrake the shocks do go stiff.

But there does not appear to be any other way of making this happen. So either a) why have they fitted this or b) is the control unit telepathic?

Anyone know?

Still :confused: Gio

(Why I am so obsessed with this, God knows - I've got a J spec so it doesn't matter :D )

I tried pulling the hanbrake up on my UK car and it didn't seem to make the slightest bit of difference what-so-ever :(

Page 26 of the online manual shows this,more detail on page 25;) http://www.300zx.co.uk/cgi-bin/manual.cgi?list=ra&dir=&config=&refresh=&direction=forward&scale=0&cycle=off&slide=26&design=default&total=35

Originally posted by TonyC

Page 26 of the online manual shows this,more detail on page 25;) http://www.300zx.co.uk/cgi-bin/manual.cgi?list=ra&dir=&config=&refresh=&direction=forward&scale=0&cycle=off&slide=26&design=default&total=35

Yes mate, that's exactly what I said!

So what is telling the controller to actuate? Only the parkbrake switch AFAICS?

 

Cheers - Gio

Strange one that then.....I'm sure somebody told me about the full throttle thing...

 

Strange thing is, near my house, there is a slighlty bumpy road, now when I hit it at say constant 40mph, the bumps are soaked up just as good as a Z can do it LOL.

 

But when I gas it over them in second gear for example, passing them at 40mph but still accelerating over them, they really play havoc, I feel that they are MUCH more pronounced.

 

This is how I 'concurred' that the two systems are linked.

 

But if the system is only activated by the handbrake, WTF use is that????

 

Robert....

unless it has an inertia switch inside that activates under accelleration??

 

more investigation required!! ;)

Well maybe its me but looking at wiring diagram seems as the actuator control box is wired to the ignition switch,meaning the ecu must play a part in it when the speed increases,sends signal to actuator,the hand brake allso does same so this must in turn be there for driver preference at any speed!what ya think:confused: :D

Originally posted by TonyC

Well maybe its me but looking at wiring diagram seems as the actuator control box is wired to the ignition switch,meaning the ecu must play a part in it when the speed increases,sends signal to actuator,the hand brake allso does same so this must in turn be there for driver preference at any speed!what ya think:confused: :D

 

the ignition switch just gives a 12v live ;)

mmmmm!so maybye the actuator controller has a speed sensor that somehow reads road speed,is it possible that the actuator on top of shocker can read the speed/wheel revs? me prob way off line now but stranger things happen!:confused: :D

Originally posted by TonyC

mmmmm!so maybye the actuator controller has a speed sensor that somehow reads road speed,is it possible that the actuator on top of shocker can read the speed/wheel revs? me prob way off line now but stranger things happen!:confused: :D

 

nope!! :D nice try though.

 

you would need a separate speed sensor like the one for the ABS! ;)

Originally posted by Paul C

unless it has an inertia switch inside that activates under accelleration??

 

Unless

a) Nissan had a "d'oh" moment when specing up the UK model on the production line and gave them the front half of the wiring diag / suspension design from Japan and the back half from the US by mistake

b) we're all having d'oh moments and missing something blindingly obvious

c) the wiring diag in the manual is wrong

 

the above suggestion is the only logical idea no matter how dagenham* it is.

"When you have excluded the impossible, whatever remains, however improbable, must be the truth."

 

Still confused after all these years - Gio

 

* two stops short of barking

Could it really be a)?

 

While we're at it who designed the 300zx? We all think its such a work of engineering art it would be nice to know who it was and what else he or she or they have done.

Originally posted by WillieO

While we're at it who designed the 300zx?

Shedloads of people from Japan to US - and ever a historical link to a German called Albrecht Goertz.

 

The story is told in the excellent book "Nissan 300ZX - The Enthusiast's Companion" © Ray Hutton & MRP Ltd and the following pic is from there

 

Thanks Gio

 

Lots of stuff I never knew!

NWF WillieO - but I still can't find out why / how those damn shocks adjust! :D

 

Cheers - Gio

The answer might be 26 and 27!!

 

On the wiring diagram there are two connections coming to the terminals 1 and 6 on the shock absorber actuator controller. These are marked on the diagram 26 and 27.

 

26 and 27 are shown coming from the HICAS control unit terminal 20 and ignition live side so something is triggered by the HICAS unit.

 

I guess proving it would need a wire run from the actuator on one shocker to light a bulb whenever it does actuate.

 

Maybe it acts in high speed fast steering movements for instance.

 

Its pretty transparent if it does do anything because You are not aware of it while driving.

Originally posted by WillieO

26 and 27 are shown coming from the HICAS control unit terminal 20 and ignition live side so something is triggered by the HICAS unit.

 

OK Willie, now you've got me confused :confused: Here's the bottom half of the page RA-26 which I got from the (Dutch) manual link. IIRC this was only a copy of our manual which Lymon put up while our forum site was being moved / recreated. I am probably being dimmer than a very dim thing but can't see any link to HICAS?

 

 

:confused: Gio

That was my thought Willieo about the wiring mine is a uk car and I can't see how the handbrake makes a difference .Looking at the shockers I can't see how they can adjust themselves as their is a small potentiometer type unit sat on top of the shockabsorber. which I think works for the hicas so the ecu can measure the amount or turn on rear wheels what do you think??

Richard

Originally posted by syko

That was my thought Willieo about the wiring mine is a uk car and I can't see how the handbrake makes a difference .Looking at the shockers I can't see how they can adjust themselves as their is a small potentiometer type unit sat on top of the shockabsorber. which I think works for the hicas so the ecu can measure the amount or turn on rear wheels what do you think??

Richard

 

no, no, no!!

 

 

the h/brake switch is there as a diagnostic aid

 

the unit on top of the shock is not a potentiometer, its an actuator which adjusts the pressure of the shock from soft to hard.

Richard

The actuator is a little motor drive gizmo that turns a blade through a quarter turn and back again to change the valving to hard. The piston rods are hollow and this blade goes down the centre of the piston rod.

I played with it when I replaced my rear shocks.

 

The wiring diagram in the pdf manual on 3/4 pages does show the 26 and 27 coming from the HICAS controller and a 26 and 27 going into the shock absorber control unit also to terminals 1 and 6 as with the handbrake diagnostic.

 

Still cant figure out when it works though apart from the diagnostic test as Paul says.