What Should I Do To My Gtr

[hrd-hr30]

Precisely.  The explanation came from the original R32 GT-R test drives done by both Wheels & by Car magazine.  The description in Wheels is as follows:

"Nissan's sophisticated Super HICAS system works in two distinct steps; initially in reverse phase (with the rear wheels turning through a small arc in the opposite direction to the front) before moving to the parallel phase."

Car was a bitmore effusive:

"The rear wheels counter-steer to help the Skyline turn into the corner, and then steer in the same direction as the fronts, to help stability.... At high speed, though, the maximum movement is approximately 0.3 degrees"

Unfortunately neither nominate a speed at which the system works/stops working.  From what I understand it changes phases, ie from counter steer to same phase when you get on the accelerator.

<{POST_SNAPBACK}>

and I wouldn't expect them to. I kinda expected this explanation of HICAS wasn't from any sort of technical source. I think I'll stick with this explanation:

Nissan pioneered the world's first practical 4WS system, HICAS (High Capacity Actively controlled Suspension), which was announced in 1985. HICAS provides transient (or delay) control over the steer angle of the rear wheels in accordance with the vehicle speed and the reactive force of front wheel steering maneuvers. With this system, the rear wheels are steered in the same phase or direction as the front wheels. This increases the handling stability capacity of the vehicle and makes it possible to obtain optimum steering response and stability to match the vehicle speed.

Author

Eguchi, T., Sakita, Y. Kawagoe, K., Kaneko, S., Mori, K. and Matsumot, T., 'Development of “Super Hicas”, a New Rear Wheel Steering System with Phasereversal Control', SAE Technical Paper 891978, 1989, pp.14951504.

Nissan Motor Co., Ltd

HICAS uses steering angle and road speed to determine what to do at what time. it has a maximum of 1 degree movement, and operates between roughly 20 and 120kph.

I very much doubt it ever countersteers first before settling into same phase steering (edit: on the racetrack, which is what we're talking about...) I've never seen any credible information to suggest this is the case, and from an engineering point of view, it's difficult to see why they would design it that way.

Edited December 14, 2005 by hrd-hr30

[djr81]

and I wouldn't expect them to. I kinda expected this explanation of HICAS wasn't from any sort of technical source. I think I'll stick with this explanation:

HICAS uses steering angle and road speed to determine what to do at what time. it has a maximum of 1 degree movement, and operates between roughly 20 and 120kph.

I very much doubt it ever countersteers first before settling into same phase steering. I've never seen any credible information to suggest this is the case, and from an engineering point of view, it's difficult to see why they would design it that way.

<{POST_SNAPBACK}>

Gees mate, you put a pretty high standard on your information sources. Thing is the information that both Wheels & Car magazine would have come straight from Nissan - the magazines (usually) don't make this stuff up & instead rely on the manufacturers to provide it.

The one degree mentioned is at lower speeds - 0.3 degrees at higher speeds which would seem to be over 120km/h from your source.

There were several generations of HICAS are you sure the SAE paper is from the R32, not the R31? Bit confused what "Phasereversal" refers to if not opposite phase steering...

From an engineering viewpoint they would design it to opposite phase on turn in to help the front heavy car turn into the corner.

Edited December 14, 2005 by djr81

[hrd-hr30]

no, that could probably make the car unstable in certain conditions - not a goal most production car engineers would be looking for. especially if as widely held opinion goes, HICAS is designed to produce understeer...

Yes, I will take the technical paper written for the Society of Automotive Engineers (SAE) and written by the Nissan Engineers that developed Super HICAS system over what a couple of motoring journos wrote in a car mag, and repeated as chinese whispers for 15 years.

Obviously, if the system steers counter phase at lower speeds, its needs phase reversal control to handle situations that are borderline or where that speed is transgressed mid corner. That was easily explained...

And the system is apperently only operative between those speeds, as I said in the last post. So at speeds over 120kph (approx) HICAS is inactive - ie no rear steer.

I believe the motoring journos could easily have misunderstood the explanation given to them by Nissan.

[djr81]

no, that could probably make the car unstable in certain conditions - not a goal most production car engineers would be looking for. especially if as widely held opinion goes, HICAS is designed to produce understeer...

Yes, I will take the technical paper written for the Society of Automotive Engineers (SAE) and written by the Nissan Engineers that developed Super HICAS system over what a couple of motoring journos wrote in a car mag, and repeated as chinese whispers for 15 years.

Obviously, if the system steers counter phase at lower speeds, its needs phase reversal control to handle situations that are borderline or where that speed is transgressed mid corner. That was easily explained...

And the system is apperently only operative between those speeds, as I said in the last post. So at speeds over 120kph (approx) HICAS is inactive - ie no rear steer.

I believe the motoring journos could easily have misunderstood the explanation given to them by Nissan.

<{POST_SNAPBACK}>

Maybe I missed the point, but how are of the explanations inconsistant. At high speed (ie above 120km/h) the HICAS may well drop out, or atleast stop opposite phase steering on turn in. Certainly Honda arranged their system to work in that way & from what I can remember so did Nissan. At lower speeds, from my understanding it uses a reverse phase on turn in to corners. From what I have experienced with the HICAS connected & the subsequently not connected that is what it feels like to me.

As for Chinese whispers, I was looking at the original article, so I don't know. Maybe all the different car magazine journo's all misunderstood all the engineers.

[Beer Baron]

i have just checked my japanese GTR book. It has a few pages on hicas and how it works (all in japanese) but it does have a diagram which shows the rear wheels countersteering on turn in, then steering in sympathy on corner exit. I'll post it up in a min.

[Beer Baron]

here it is. I just cut out the important bit:

that seems pretty concrete to me. If anyone wants to have a go at translating the text i'll post the whole lot up.

[RellikZephyr]

also i have this pic to back up beer barons statement

super HICAS being GTR only i believe

[hrd-hr30]

this is a far cry from what everyone always says about HICAS always countersteering then changing to on phase steering when cornering, and using that as a reason to disable it on the racetrack because they say it gives unpredictable response. which is what we're talking about. I think that comes from a misunderstanding or oversimplification of the system - exactly like you've done with those photos - using it as concrete proof when you don't even know what the text says... At least it corroborates what the SAE paper says that it does not counter phase rear steering at 'high' speeds. One photo here and there does not mean that is all HICAS ever does...

The system is only operative up to 120kph, so the fact that it counter steers at "low speeds" - whatever that is according to HICAS, but you would imagine its well below 120kph where it stops working - is pretty irrelevant to race track handling.

I didn't notice any inconsistent handling at Mt Cotton which has corners from tight 1st gear hairpins to ~90-100kph sweepers around the top of the hills with a sharp crest and the odd bump thrown in for good measure. Or at Bathurst on the Conrod Supersprint entering Caltex Chase at ~220kph with a couple of ~100kph entry LH corners, or even on the Mountain straight hillclimb, with everything from a ~150-160kph sweeper to 90-100kph tigh, banked bumpy turn at the cutting and then alot of fast 3rd gear turns with crests hiding apexes and stuff. I never once felt anything but confident fromt the suspension/steering response. So I've seen a fairly wide range of corners on the limit, and I've never seen the 'problem' everyone always blames on HICAS. That's why I started looking for real info on how it works rather than rely on general opinion here. My GTR handles absolutely awesome for such a heavy car, and I can't see any reason to remove the HICAS - yet anyway. There's a couple of other things I want to do with the suspension before I'll worry about HICAS. I don't think it should be scrapped immediately you start even thinking about track days as everyone recommends. There are other areas that will give greater benefits first.

Super HICAS is on Stageas too, at least - it may be on other models as well. And so far we've been talking about R32 mainly (ie what RellikZephyr drives, and what those motoring journos were reffering to), not the later electric system. I haven't read anything on that to know if it differs in its operation from the early electro-hydraulic HICAS.

[djr81]

this is a far cry from what everyone always says about HICAS always countersteering then changing to on phase steering when cornering, and using that as a reason to disable it on the racetrack because they say it gives unpredictable response. which is what we're talking about. I think that comes from a misunderstanding or oversimplification of the system - exactly like you've done with those photos - using it as concrete proof when you don't even know what the text says... At least it corroborates what the SAE paper says that it does not counter phase rear steering at 'high' speeds. One photo here and there does not mean that is all HICAS ever does...

The system is only operative up to 120kph, so the fact that it counter steers at "low speeds" - whatever that is according to HICAS, but you would imagine its well below 120kph where it stops working - is pretty irrelevant to race track handling.

I didn't notice any inconsistent handling at Mt Cotton which has corners from tight 1st gear hairpins to ~90-100kph sweepers around the top of the hills with a sharp crest and the odd bump thrown in for good measure. Or at Bathurst on the Conrod Supersprint entering Caltex Chase at ~220kph with a couple of ~100kph entry LH corners, or even on the Mountain straight hillclimb, with everything from a ~150-160kph sweeper to 90-100kph tigh, banked bumpy turn at the cutting and then alot of fast 3rd gear turns with crests hiding apexes and stuff. I never once felt anything but confident fromt the suspension/steering response. So I've seen a fairly wide range of corners on the limit, and I've never seen the 'problem' everyone always blames on HICAS. That's why I started looking for real info on how it works rather than rely on general opinion here. My GTR handles absolutely awesome for such a heavy car, and I can't see any reason to remove the HICAS - yet anyway. There's a couple of other things I want to do with the suspension before I'll worry about HICAS. I don't think it should be scrapped immediately you start even thinking about track days as everyone recommends. There are other areas that will give greater benefits first.

Super HICAS is on Stageas too, at least - it may be on other models as well. And so far we've been talking about R32 mainly (ie what RellikZephyr drives, and what those motoring journos were reffering to), not the later electric system. I haven't read anything on that to know if it differs in its operation from the early electro-hydraulic HICAS.

<{POST_SNAPBACK}>

Most of the entry points for corners on tracks (Atleast over here) at taken in third gear in the range of 4000rpm to 4500rpm. That is according to my data logger. Makes turn in for those corners at around 100km/h - well inside the HICAS working range. Second gear corners will be much less than that - the HICAS effect feels more pronounced in slower corners.

Attached are a couple of photos from Wanneroo - specifically the turn in to CAT corner at the end of pit straight. One shows the usual amount of steering lock, the other what happens when the back end breaks loose...

In any case if you are happy that the HICAS helps you get around the track quicker good luck to you. I wasn't, changed it and am happy with the result. So everyone is happy. Gotta be, um, happy with that.

Edited December 15, 2005 by djr81

[hrd-hr30]

Most of the entry points for corners on tracks (Atleast over here) at taken in third gear in the range of 4000rpm to 4500rpm.  That is according to my data logger.  Makes turn in for those corners at around 100km/h - well inside the HICAS working range.  Second gear corners will be much less than that - the HICAS effect feels more pronounced in slower corners.

<{POST_SNAPBACK}>

I find mine a bit unresponsive at 4000-4500 in 3rd. And since 2nd can easily hit 120kph at a conservative 8000rpm, that's the gear I generally use for those kind of speeds. Yes, its inside the HICAS working range, but it would pretty certainly be in the high speed end of the HICAS operation without the phase reversal and the supposed unpredictability everyone complains about. There wouldn't be too many corners on Australian racetracks where entry speed would be below about 80-90kph for any reasonably setup GTR on race rubber. You'd pretty much need hillclimbs for lower speed corners, and MtCotton is about as tight as they come. I did a practice day there in the pouring rain and didn't notice the unpredictable HICAS trait. But then, I'm not afraid of a bit of sideways action.

[hrd-hr30]

oh, just saw the pics you added. that's an awful lot of lock on the first shot! here's a pic of mine mid corner in the cutting at Bathurst (if it works )

[Beer Baron]

this is a far cry from what everyone always says about HICAS always countersteering then changing to on phase steering when cornering, and using that as a reason to disable it on the racetrack because they say it gives unpredictable response. which is what we're talking about. I think that comes from a misunderstanding or oversimplification of the system - exactly like you've done with those photos - using it as concrete proof when you don't even know what the text says...

<{POST_SNAPBACK}>

ease up a little mate. you said: "I very much doubt it ever countersteers first before settling into same phase steering. I've never seen any credible information to suggest this is the case, and from an engineering point of view, it's difficult to see why they would design it that way."

my response clearly shows that yes, under certain conditions it does counter steer from the rear. the picture i posted up shows that pretty clearly. it's taken from a nissan japan brochure on R32 GTRs so i would place some value on it's accuracy. I didn't make a value judgement on whether it's a bad thing or not. Though you did, saying that it would make the car nervous and unpredictable. I didn't state whether it does it at 89 kmh or 46 kmh or whatever. you have drawn that into this afterwards. I was just trying to impart some information from the horses mouth, not get into a great debate.

[hrd-hr30]

ease up a little mate. you said: "I very much doubt it ever countersteers first before settling into same phase steering. I've never seen any credible information to suggest this is the case, and from an engineering point of view, it's difficult to see why they would design it that way."

my response clearly shows that yes, under certain conditions it does counter steer from the rear. the picture i posted up shows that pretty clearly. it's taken from a nissan japan brochure on R32 GTRs so i would place some value on it's accuracy. I didn't make a value judgement on whether it's a bad thing or not. Though you did, saying that it would make the car nervous and unpredictable. I didn't state whether it does it at 89 kmh or 46 kmh or whatever. you have drawn that into this afterwards. I was just trying to impart some information from the horses mouth, not get into a great debate.

<{POST_SNAPBACK}>

"ease up"? if someone's getting worked up here, it isn't me.

I edited that post to clarify what I was saying a good 2hrs before you quoted it just now without that edit, and even bolding it, to suit your purpose. I never meant to give the impression that HICAS absolutely never counter steers - I was talking about it counter steering yesterday and again earlier today if you care to look. But I freely admit, that post of mine you quoted was not clear, and still kinda reads that way. Frame of reference is racetrack handling problems with HICAS though...

And I said "could" make the car unstable "in certain conditions", not " that it would make the car nervous and unpredictable" as you claimed, but don't let the facts get in the way of your story...

And you have said before that HICAS makes the rear end unpredictable - sounds like a value judgement to me, which is fine. I've made my personal opinions on the feel of the system, but then I never said I didn't like you just did.

The issue is that it seems to be commonly held opinion here that HICAS is crap because it always countersteers on turn-in and that makes the handling unpredictable, and should be immediately scrapped as soon as you as much as think about a track day. I'm saying it doesn't always countersteer on turn in, and I doubt that it ever would on a racetrack, and that it doesn't seem to make the handling of my GTR unpredictable or unsettled at all either on the reacetrack or off it for that matter.

what are you so worked up about Beer Baron?

Edited December 15, 2005 by hrd-hr30

[Sydneykid]

Interesting discussion, having driven over 20+ Skylines on the track, with and without HICAS, I feel quite confident in saying that it is not my friend and I would remove it at the earliest opportunity.

The transition, as shown in the following diagram, between the rear steering angle in (1) and (2) confirms what I can feel. When cornering at high slip angles, having the rear wheels change direction is not good for controlling the traction. Personally I like to do that with the throttle, and for people who trail brake it would be quite disconcerting.

It's all about consistency in feel and feedback, the speed sensitivity in the HICAS software just makes that consistency even more difficult to achieve. I have a dislike of entering a corner at X - 1 kph on one lap and having the HICAS take some action. Then in the same corner on the next lap at X + 1 kph take a different action. I don't really care what kph X represents, chances are I will find at least one corner with X as its appropriate speed on most circuits.

Since disabling HICAS is a simple zero cost modification, I don't feel that I have to sacrifice/delay other mods. It is only if I wish to take advantage of the potential weight saving that I have to spend $150, which doesn't buy much else anyway.

cheers

PS; Note the following picture of Stagea RSFour rear suspension and the absence of HICAS;

[Beer Baron]

"ease up"?    if someone's getting worked up here, it isn't me.

I edited that post to clarify what I was saying a good 2hrs before you quoted it just now without that edit, and even bolding it, to suit your purpose. I never meant to give the impression that HICAS absolutely never counter steers - I was talking about it counter steering yesterday and again earlier today if you care to look. But I freely admit, that post of mine you quoted was not clear, and still kinda reads that way. Frame of reference is racetrack handling problems with HICAS though...

And I said "could" make the car unstable "in certain conditions", not " that it would make the car nervous and unpredictable" as you claimed, but don't let the facts get in the way of your story...

And you have said before that HICAS makes the rear end unpredictable - sounds like a value judgement to me, which is fine. I've made my personal opinions on the feel of the system, but then I never said I didn't like you just did.

The issue is that it seems to be commonly held opinion here that HICAS is crap because it always countersteers on turn-in and that makes the handling unpredictable, and should be immediately scrapped as soon as you as much as think about a track day. I'm saying it doesn't always countersteer on turn in, and I doubt that it ever would on a racetrack, and that it doesn't seem to make the handling of my GTR unpredictable or unsettled at all either on the reacetrack or off it for that matter.

what are you so worked up about Beer Baron?

<{POST_SNAPBACK}>

i quoted you post without your edit because it wasn't edited when i was replying to it last night. I was simply responding to how i read your post. what i read was: "it never countersteers, nissan wouldn't have designed it that way". I was just trying to answer your post with some acurate (albiet a little bit non-specific) info. I boldened it to emphasise the bit i was replying too.

BTW i don't think i've ever said before that hicas makes the rear end unpredictable. and FTR i still have hicas on my GTR, though i will be locking it. if i decide i liked it better operative, then it will be changed back. Also i've never told anyone to look at disabling hicas as a first step towards driving on the track.

mate i don't know if it's just the way i am reading your posts but it seems like you want to pick an argument over every little thing. please don't. I was just trying to share some information with you, that i went to the trouble of digging out of the bookcase and scanning so you could see it. so there is no need to try and shoot me down.

[Beer Baron]

Since disabling HICAS is a simple zero cost modification, I don't feel that I have to sacrifice/delay other mods.  It is only if I wish to take advantage of the potential weight saving that I have to spend $150, which doesn't buy much else anyway.

cheers

<{POST_SNAPBACK}>

gary, what is the simplest zero cost way to disable hicas? I'm guess just putting some washers between the tie rods and the rack? will this have any adverse affect on the pump (tyring to move the rack even though it cant)?

I ask as i'm quite keen to give it a go without hicas so i can compare to what it's like atm.

Thanks

[Sydneykid]

gary, what is the simplest zero cost way to disable hicas? I'm guess just putting some washers between the tie rods and the rack? will this have any adverse affect on the pump (tyring to move the rack even though it cant)?

I ask as i'm quite keen to give it a go without hicas so i can compare to what it's like atm.

Thanks

<{POST_SNAPBACK}>

All the Tomei R32 HICAS locking kit does is provide 2 washers and a box of simple electronics to stop the HICAS dash warning Light coming on. For testing you can just lock the rack with suitable sized washers and ignore the HICAS dash warning light, or pull the globe.

When you do lock the rear rack you will find that you have lots of toe in, so you will have to wind that out. You don't actually have to do a wheel alignment (although you could). Before I touch anything, I just measure the distance from the rack to the steering arm ball joint (on both sides). Then after I have locked the rack I adjust the steering arms so as I get the same distance as I had before I touched anything. That way I end up with the same static wheel alignment as I had before I locked the rack, so it's a fair back to back test.

I don't know one single person who has tried locking the HICAS who hasn't found it to be noticeably more confidence inspiring on the circuit.

cheers

[Beer Baron]

yep, that's what i thought. thanks gary i will give it a go, i'll have a quick measure and find some appropriate sized washers.

[t01-100]

With any GTR being used where hi G forces are in place one of my first steps would be to install a trap door style sump baffle... it will prevent engine failure via oil stavation in an RB26 and are cheap insurance, but a pain to fit.

[djr81]

I find mine a bit unresponsive at 4000-4500 in 3rd. And since 2nd can easily hit 120kph at a conservative 8000rpm, that's the gear I generally use for those kind of speeds. Yes, its inside the HICAS working range, but it would pretty certainly be in the high speed end of the HICAS operation without the phase reversal and the supposed unpredictability everyone complains about. There wouldn't be too many corners on Australian racetracks where entry speed would be below about 80-90kph for any reasonably setup GTR on race rubber. You'd pretty much need hillclimbs for lower speed corners, and MtCotton is about as tight as they come. I did a practice day there in the pouring rain and didn't notice the unpredictable HICAS trait. But then, I'm not afraid of a bit of sideways action.

<{POST_SNAPBACK}>

A few comments Harry:

Torque characteristics & redlines vary from motor to motor. Having overlaid the torque curve with the in gear speeds, for my car anyway, the change up point works out to be under eight thousand - so it makes sense to use third instead of revving the berries out of it in second. Yours may be different & produce a different result. By the way if anyone wants to know how to do this I am happy to post it up.

Not every circuit in Australia is Mt Panorama & not every corner is Caltex Chase. There are a plethora of second gear corners (My local circuit at Collie has two, the short course at Wanneroo has one, hillclimb courses usually have a couple) & slower speed third gear corners. The reason the photo I posted up earlier shows a heap of understeer was that, having disconnected the HICAS the car was understeering badly on turn in. I spent most of the day dropping the rear tyre pressures & subsequently messing around with springs, roll bars, camber & caster settings. For the record it feels like phase reversal to me on turn in & disconnecting the HICAS made the thing understeer more on turn in.

Sideways action is fine - even fun. It is not necessarily quick & on turn in to a corner it is definately neither fun nor quick. One of the problems with car setup is that alot of people (Not necessarily you) confuse bravado & oversteer with quick & effective driving. The idea is to get the car around the circuit as quickly as possible with the least amount of drama, not necessarily keep the spectators amused.

The important thing is to have a go & have some fun. By the by, I don't have sump baffles & with cornering gees reaching into the 1.3 + range I have never had oil surge problems. Just overfill the sump by about a litre. Obviates the need for such an expensive modification for cars that only occassionally hit the track.