Should I delete Super HICAS? Unexpected snap over-steer in the dry and strange recovery oscillation?

Discussion in 'Z32 Technical' started by bobbs, Mar 22, 2019.

?

Delete HICAS?

  1. Yes. Chuck it in the bin

    80.0%
  2. No. You suck at driving

    20.0%
  3. Yes... And you still suck at driving

    0 vote(s)
    0.0%
  1. bobbs

    bobbs Member

    Messages:
    341
    Likes Received:
    0
    Trophy Points:
    16
    Admittedly, I can't blame HICAS for my bad driving, and I should probably do a full rebuild on the rear sub frame... but I had a bit of a moment this morning where the rear unexpectedly started to slide out when powering out of a sweeping turn. I lifted and only counter-steered mildly which started the snap oversteer / tank slapper oscillation maybe 2~3 times back and forth. I was only able to stop the oscillation by getting back on power.
    But the thing is, I'm not sure if its the HICAS system, but especially when cornering at speeds (It was very noticeable at Eastern Creek Raceway), the rear sometimes feels like there is a strange artificial over-steer sensation, but without a resisting force you'd expect when the wheels do skid... Kind of feels like it handles like a shopping trolley - not in control. It definitely feels different to every other RWD car I've owned.
    I'm not sure how the HICAS system works or what its doing and when... I haven't really worried about deleting it until now.
    So does anyone know what/how/when it reacts when you lose rear traction? Should I delete HICAS or am I overthinking it and just improve my driving with the HICAS system still operational?
     
  2. Fists

    Fists Well-Known Member

    Messages:
    1,724
    Likes Received:
    38
    Trophy Points:
    48
    Does it have the hydraulic or electric rear steering rack? You can just unplug the power steering controller near the ECU next time you're at the track and so long as nothing is physically broken it'll lock the rear rack so you can see if you prefer it without. Unplugging the controller will also give you a single rate power steering strength so the wheel will be heavy at low speeds and a little light at high speed but should be manageable on track.
    The Z32 does have some pretty odd behaviour in the rear end even without hicas and it can be exaggerated by problems or poorly chosen stiffness of the springs, shocks and sway bar.
     
    bobbs likes this.
  3. bobbs

    bobbs Member

    Messages:
    341
    Likes Received:
    0
    Trophy Points:
    16
    Its the hydraulic type... Is it possible to just disconnect the controlling hydraulic actuator/solenoid instead of disabling over riding the whole power steering system? It might be worth trying it out with it disabled before I waste money on parts.
    It also has Tein Flex Z coilovers. I suspect the spring rates are way over sprung.
    With stock springs, weight transferred easily, predictably and seemed under/oversteer neutral. Now it understeers easily diving into corners and is oversteer happy on corner exits. Roll bars are just stock... Though I assume stronger ones would only make it worse?
    Though I really want to rebuild the whole power steering system as its a leaky mess. I also want to rebuild the steering rack myself or replace with a reconditioned one. So it might be a good opportunity to delete the HICAS plumbing.
     
  4. ryzan

    ryzan Black Mesa? Fat chance...

    Messages:
    3,560
    Likes Received:
    21
    Trophy Points:
    38
    Never lift, that's probably the cause of your issue. But I'd also remove it, nobody's ever said it's made them a faster/better driver.
     
    bobbs likes this.
  5. Chrispy

    Chrispy Pretentious Upstart

    Messages:
    16,452
    Likes Received:
    367
    Trophy Points:
    83
    I'm not a fan of it.

    Also a good idea to replace the bushings in your control arms, they'll be quite old by now!
     
    bobbs likes this.
  6. bobbs

    bobbs Member

    Messages:
    341
    Likes Received:
    0
    Trophy Points:
    16
    Looks like 2 other people say keep the hicas system. What would be the benefits? As far as I understand, those benefits turn into disadvantages as soon as you lose traction... Or is there other more important reasons people like drifters delete it. Admittedly, i need to spend more money on track days to further improve my skill. As it stands, i still dont understand what its doing and feels confusing to drive at its limit. If its explained to me, i might be able to see its advantages and utilise it properly.
     
  7. rob260

    rob260 Moderator Staff Member

    Messages:
    14,833
    Likes Received:
    181
    Trophy Points:
    63
    Location:
    Sydney (North)
    Why would you attempt to repair or modify your car via opinion poll?

    There is so much information at your fingertips; spend some time understanding what the system does and then decide for yourself. There is an SAE paper available here https://www.sae.org/publications/technical-papers/content/891978/ if you’re really keen, although it has been referenced enough online that you can read the important parts without paying for the privilege.

    You mention understeer on entry and oversteer on exit -guess what the HICAS system designed to assist with...

    Read up https://drivingfast.net/oversteer/ for lift off oversteer.

    Generally speaking I prefer to delete it if only to remove all the extra plumbing...
     
  8. Fists

    Fists Well-Known Member

    Messages:
    1,724
    Likes Received:
    38
    Trophy Points:
    48
    I'm not aware of any of the track-day goers or full on racers here that have kept HICAS. I would guess the people who are recommending you keep it have never actually driven fast enough to get it to activate. Mine got binned because there were some busted sensors and cbf fixing it and dealing with all the lines.

    My set up now is an NA rear cradle which doesn't have hicas anyway with 9f/4.5r kg/mm springs and I removed the rear sway bar to stop it from lifting a rear wheel with the old crappy diff. The car has very direct handling, is predictable and pulls straight under power but pushes out when trying to turn into the corner so maybe now having hicas would actually help me out although more likely it'd just add to the number of things I have to think about. My car is a 2 seater, the 4 seaters will handle differently.
     
  9. bobbs

    bobbs Member

    Messages:
    341
    Likes Received:
    0
    Trophy Points:
    16
    I only used the poll to get a brief snapshot of popular opinion. You wouldn't know where I can find the full version of that tech paper? Nothing useful on the preview :(

    Actually when it still had stock springs and shocks, it handled really well. I never had a problem with Hicas. Sure, it still felt weird but at least it was balanced. Even with most of the bushings needing replacement.
    Ever since I installed the Tein coilovers (with the recommended spring preload) it has changed the handling quite dramatically. As I said earlier, the front now pushes out too easily on corner entry, and the rear kicks out aggressively on exit. In general, the feeling when Hicas kicks in is even more noticeable, confusing and just feels unnatural. Its also only running stock NA wheels, but decent new-ish RE003 tyres. The castor is pretty far out on one side so the alignment is actively compensating for that (until I replace the castor rods). Its a 2+0 so its handling now is quite twitchy.

    In this specific scenario I experienced, I believe its more complex than I first thought. It was multiple mistakes, combined with road conditions and badly tuned suspension. You see, it was a two lane road sweeping left, inside lane had positive camber, outside lane was negative camber.
    Mistake #1: As I was powering out of the inside line, as it crossed into the outside lane, thats when the rear kicked out.
    Mistake #2: I counter steered appropriately which was fine, but instinctively lifted.
    Mistake #3 Plus I was wearing floppy ugg boot slippers and driving like a nob on the street with a 10kg air compressor sliding around unsecured in the boot. Some cracked interior plastics as a result. I know. I'm an idiot.
    Mistake #4. Because I lifted, I wasn't able to reverse my counter steering fast enough back to straight, thus caused the over steer to swing like a pendulum.
    Mistake #5. It probably looked like I was doing perfect invisible slalom.
    I guess I just need practice controlling slides. Perhaps learning drift properly would help me unlearn these bad habits.

    I guess in hind sight, there were other more contributing factors and elimination of the HICAS probably wouldn't have changed anything. The only advantage I can think off in favour of deleting it would be that it would handle more predictably without any surprises. It might be useful in gymkhana slaloms, but that's not something I'm involved with and not something I want to suddenly kick in on the street.
     

Share This Page