Four Wheel Steering - What happened ?

[lambs]

The Skyline HICAS system moves the whole subframe I beleive, not just the wheels...

The original HICAS (Type 1, if you like) was used on R31 Skylines and had 2 small rams that moved the rear suspension subframe (R31's used trailing arm suspension v similar to datto 1600's, 280ZX and R30 Skylines).

Super HICAS (Type 2) was used on R32, R33 and R34's. In the case of R32's there is a single, dual direction hydraulic ram with a type of tie rod end linked to each rear wheel. It looks a bit like a steering rack and does actually 'steer' the rear wheels. In the case of R33's and R34's the 'rack' is electrically operated.

However in each case the amount of rear wheel movement is small. In the case of the R32 GTR it amounts to only 1 degree (3mm ram extension). Also it has no effect below about 80km/hr, so we're not talking about parking or narrow street manoeuvring here (well, maybe for some )

I'd be interested to see some links to these reports of 'sudden failures' as I've never heard of anything like that being reported till now.

In the automotive world a lot of these 'gimmicks' are marketing driven.

[carazy]

I think the problem with 4ws is it's very unpredicable. I nearly crashed a mates car with 4ws ( honda prelude) because it doesn't know if it wants to behave like a fwd car or a rwd car.

[Aloysious]

hmmm, i was under the impression it only really (should have) worked at low speeds.....

[Jamx6]

I specifically avoided the 4WS MX6 for the above reasons when I was buying an MX6 turbo all those years ago.

A lot of the manufacturers in Japan threw it on all sorts of models...including an SVX! there were 1000 of them made in 1991 for sale in 1992 at a huge premium over normal - you could still buy one, brand new, in 1995!!! They were shunned in a massive way! The rear steering used similar componentry to the 3000GT/GTO

Not enough return for the complexity and cost was the end of 4ws from what I can see

[Sturmovik]

Quite a few SUV/Pickup Chevys has optional 4ws....

QUADRASTEER System
Specifically equipped Suburban three-quarter-ton models are available with QUADRASTEER by Delphi, an available four-wheel steering innovation.
The touch of a button takes this innovative system from two-wheel steering (2WS) to four-wheel steering (4WS). And 4WS TOW provides improved stability when towing at speeds above 20-25mph by allowing the rear wheels to turn in conjunction with the front wheels and because of the wider rear track.
With QUADRASTEER, Suburban three-quarter-ton has a best-in-class turning diameter of 36.5 feet.(1) It's like having the steering maneuverability of some smaller vehicles while you're driving a large sport utility vehicle.

[Sturmovik]

Heres a video of it in action.

http://www.delphi.com/images/automot..._ease-high.mov

[BigMuz]

I once drove an MX6 in a spriteful manner it felt unsafe and did things cars shouldnt.
Theory was great in practice it just didnt work.

spriteful! SPRITEFUL!

Did you go to journo school with Paul!

But seriously, I had a mate with an integra and it was great for driving around carparks, and the most dangerous unpredictable wild bitch when you pushed it hard, especially around slower corners, where it seemed to not know if it should countersteer or (whatever the opposite of countersteer is).

Muz

[poid]

if you only fang a 4WS car once or twice it will seem unpredictable (which is why the prelude is, or was, one of the most crashed cars), but once you are used to it the steering is quite good at high speed and the ability to make the tightest turns when parking is very very useful.

I am talking about my experiences with the gen3 prelude though, which is a mechanical system and not electronic. It also breaks down less than the gen4's electronic system which is notorious for soldering faults in the steering ECU causing loss of 4WS when restarting a hot car

[Paddington]

was an article on this very topic in todays The Age newspaper.

[Babalouie]

I think one of the reasons is that the car makers have found cheaper ways of doing the toe-in thing that supposedly gives better high speed stability. Tuning toe change under load with suspension bushings of varying softness is probably much more of an art form now.

The super-turning circle from the early Maz/Hon systems were prolly not such a great selling point anyway.

[carazy]

That's true Bablouie. The RX7 has a rear suspension system that does that with out being connected to the steering system

[Babalouie]

That's true Bablouie. The RX7 has a rear suspension system that does that with out being connected to the steering system

If you're thinking about the FC RX-7, that's very true, but nowadays it's more subtle without that bulky triaxial hub that the FC has.

MX5 and S2000 just have conventional looking double wishbones but with one particular bush being softer than the rest. On the other hand, the Lexus IS200 has a toe control arm that just "pulls" the alignment into toe-in when the car body-rolls.

[Jim]

marketing gimmick. it was good in carparks for the likes of the MX6, but that was mainly because it had such a shithouse turning circle without it. newer cars (even FWD) have sorted out the turning circle issue it seems, so don't really need 4WS. My R32 4WS was barely noticable, except on the big loop coming onto the freeway every morning. it'd fight you all the way around and you'd end up in this dance between understeer and oversteer. it's a much nicer car in hard corners without it.

[Datto-Zed]

Also, the nissan systems, as reported on various forums around the net, occasionally fail and throw the car into a wild spin.

The stories I heard were at about the 70-80km/h mark. Not fun I imagine.

I'd be interested to see some links to these reports of 'sudden failures' as I've never heard of anything like that being reported till now.

A mates R32 has such a problem after pulling donuts... It seems the HICAS computer doesn't like the combination of the steering being close to full lock and the rear wheels doing high speed at the same time. So it has a bit of a spaz when you hit 80kph and it turns on. The rear wheels will turn fully in one direction and the car will crab walk down the road. Pull over, turn it off then back on and it's fine again.

[NAliberty]

I think one of the reasons is that the car makers have found cheaper ways of doing the toe-in thing that supposedly gives better high speed stability. Tuning toe change under load with suspension bushings of varying softness is probably much more of an art form now.

The super-turning circle from the early Maz/Hon systems were prolly not such a great selling point anyway.

Subaru claims to have this feature on all of it's >1989 models. They call it Passive Rear Wheel Steering. I had a good thrash on the track today actually and it it most certainly noticeable at higher corner speeds.