4ws - not the usual questions...

[Whoodoo]

I've done lots of searching and looking around at 4ws stuff. The bulk of the threads are either 'how do i fix it' or 'how do i get rid of it' sort of things. I am playing around with something much different.

For those of you who aren't familiar with the honda prelude, it also had the option of 4ws. However, it was always active and behaves quite differently than ours does. When turning the wheel, the rears will initally turn the same direction as the front (like ours). However, when continuing to turn the wheel, they then return to neutral and begin to go in the opposite direction, giving the car a very nimble demeanor.

Now on to the question. Does anyone here have any clue how difficult or worthwhile it would be to swap in a rear rack from the prelude? I know that the 3rd gen prelude was a mechanical linkage, but i understand that 4th and 5th gen were hydraulic/computer controlled. Would there be enough room for +-5.3 degrees of rear steer?

 

[Terry Posten]

Don't even try it. It is more than just a rack thing and a CPU thing. Our rear arms will not "give" that much. The rack on our cars just force the arms against the rubber bushings and there is no more play to go further.

The other reason is that the rear drive will over power all that and you will get slingshot all over the place. It will feel like your rear is always trying to drive around you.

 

[Brunoboy]

Prelude 4ws isn't safe at all anyways, tre3zy homie is my homie too and the other day his 4th gen lost it all on The freeway and I'm sure that 4ws didn't help when he did that slow lane to fast lane doing a 180*.......

 

[Whoodoo]

ok ok. So you've managed to convince me that its not the greatest idea. One more check to the 'your a dumbass' column /ubbthreads/images/graemlins/frown.gif

 

Don't worry man, ideas like this is how we got the coil on plug setup, Evo 1st gear and the Evo suspension... I'm sure they all sounded crazy at first.

 

I WISH we had the prelude's 4WS! The preludes have the great 4WS, great in the rain! /ubbthreads/images/graemlins/jawdrop.gif

 

[Whoodoo]

Thats exactly what i was thinking, but the issue of power to the rear wheels came up and is honestly a very good point. If you are mid corner and have half of the power going to the rear wheels while they are at 5.3 degrees of opposite lock, you will certainly experience very odd and unpredictable handling.

I guess it didnt hurt to throw it out there though. Thanks for the kind words.

 

[Dialcaliper]

Preludes had two different types of rear steer. The early (3rd gen I think) preludes had a purely mechanical 4WS system with a pushrod that runs exactly where a rear driveshaft would, and a rear rack that sits right where our rear diff would (it even looks like a differential) Here's a picture I came across. They used a kind of wacky pushrod/gearing setup to get the wheels to turn into the turn first, and then to opposite lock.

The later models had an electronically controlled, hydraulic operated 4WS system, which really isn't any more reliable than ours (possibly less so due to the electronics). The only difference is that those cars tend not to sit around deteriorating on jackstands as much as ours, which causes more problems with hydraulic systems and balljoints.

 

[RayH]

You want to try something crazy, try crossing the high pressure lines that go from the front rack to the rear. As far as I know, nobody has actually tried this but it should make for some twitchy handling. The HICAS system used on older Nissans is probably closest in operation to ours and most owners disabled that one also.

 

4ws was introduced during the 90's technology hype. (Similar to rx7 FD3S sequential turbo idea)
It's cool, but it's not really necessary? /ubbthreads/images/graemlins/cool.gif

 

[Hertz]

Sequential turbos are not that crazy, just expensive and take up a lot of room... but awesome for HP curve. 4WS, however, is a solution without a problem. /ubbthreads/images/graemlins/smile.gif

 

[1990ggsxnj]

Unless you've just purchased a new Yukon Denali and are trying to Parallel Park for the first time in the city /ubbthreads/images/graemlins/rofl.gif

Apparently that 4ws rocked for parking purposes.

 

[1990ggsxnj]

Quoting Terry Posten:
The other reason is that the rear drive will over power all that and you will get slingshot all over the place. It will feel like your rear is always trying to drive around you.



Why not, Monster Trucks do it /ubbthreads/images/graemlins/grin.gif

 

[misterfixit]

Old honda preludes (89-91) have a hydraulic set up. the bb model '92 on? has an electro mechanical ball screw actuator in the centre of the rack where our diff is, so would be a game to get it to work.

Interestingly our steering system could be made to steer both ways using the hydraulics. Mitsubishi themselves patented the set up and schematics for the valve block at the rear of the car. Its US patent number 4,917,205. 17th april 1990 and MR. Kobayashi, Takizawa and Fujkuyama (inventors) are to be thanked!

Here is the link to it. (view images to see the document)
click

Some of the referenced documents are interesting reading too!

Rich

 

Quoting Hertz:
Sequential turbos are not that crazy, just expensive and take up a lot of room... but awesome for HP curve. 4WS, however, is a solution without a problem. /ubbthreads/images/graemlins/smile.gif


Have you seen the fd's "rats nest"? If you don't call that crazy, what is? lol..
I cried day&night trouble shooting that darn thing. /ubbthreads/images/graemlins/banghead.gif

 

[yeti]

Dead horse I know ..... /ubbthreads/images/graemlins/idea.gif


Was ALWAYS wondering if there's a way to actuate the 4WS all the time, maybe fill up a pressurized reservoir to keep it ready when under 30? miles per hour.. and have ait actuate when parking or by push switch, or have a return line and just always keep it filled and always have it filling using and returning??

Trying /ubbthreads/images/graemlins/grin.gif

 

[misterfixit]

Hydraulics is my bag. It's how i've made my living for the last ten years.

To mimmic the honda system there must be two things, see the patent I linked:
1, the rear system must recieve pressure all the time.
2, the rear needs two control valves (both configured in oppositely) and switching valve or a lock mechanism on each valve. (one normally locked, the other normally unlocked).

Below the magic speed the front pump would drive the rack opposite phase.
At the magic speed the valvlve would be locked or disconnected and the system rear pump would then run through the second valve which had been unlocked.

Easy?

Rich

 

[yeti]

Seems simple enough, anyone ever try it? or anything like it?

Would the idea of the pressurized reservoir be useful or is that to clunky and heavy?

Could the front pump create enough pressure to turn the rear wheels under the magic speed? without burning out?

Little confused about how to make this work outside of theory...

What would have to be done in physical matters?
Install line from front pump to rear with valves?

 

[bmxr152]

I am also interested in this, i have been thinking about it for a long time now. Actuate it almost like how monster trucks do would be nice for certain situation ecspecially with a welded center diff and trying to parallel park.

 

[fuel]

Has anyone looked into how the Toyota 4WS works? I can't for the life of me find the video demonstration how it works, but it had an electric valve/switch in the rack which changed the direction that the rack operates (ie opposite for low speed, parallel for high speeds), or even locks it in place dead in the center - the ST182 with 4WS has a switch on the dash to disable the 4WS while reversing to make it easier to maneuver.