All Wheel Steering Demo Vid

[DocWalt]

Figured I'd post it up again for those that haven't seen it.


Tested with a 1994 3000GT VR4. AWS is pretty visible in this video when I turn full lock. I turn full lock twice on each side, which is why you see the wheel pop out twice. At around 3/4 of the way through the video I'm jerking the steering wheel back and forth, and you can see it activate then as well.

The AWS system is same phase, meaning the rear wheels turn in the same direction as the front wheels when it activates. The AWS is controlled by a system of valves at the rear differential. There's a valve that limits the AWS to above a certain speed, so it doesn't make parking more difficult. There's also a valve that activates the AWS based on a pressure differential from the two feed lines from the front power steering rack.

The system is extremely stable for lane changes, and helps keep the rear end in check in corners. Professional drivers that have tested the AWS through slaloms say it makes the car feel "different" but they say it's also easier to go faster because the rear end doesn't slide out like it would with no AWS.

Notice the Active Aero front air dam in the video. It pops down at around 48 mph.

disclaimer: I am in no way responsible if you try this and do something stupid or hurt yourself, etc.


http://www.youtube.com/watch?v=9c9dxEnYh3Y

[MADMarc]

That's always cool to see. ...I'm just too afraid to do it on jackstands.

[DocWalt]

Eh, it's super stable. I was just dicking around with it yesterday because I had her up on jackstands bleeding the brakes. 6th gear at idle doesn't make enough power to not eventually stall, for future reference, lol.

[Blurr]

There's a valve that limits the AWS to above a certain speed, so it doesn't make parking more difficult.

Is it possible to alter this valve or modify the system to make it active all the time? I've never looked at the service manual for this system.

[Atrosity]

Would performance be better around turns when deleted the AWS all together.

[DocWalt]

Is it possible to alter this valve or modify the system to make it active all the time? I've never looked at the service manual for this system.

I'd imagine you could, but the rear pump is driven from the rear diff, so it would need to be modified to pump using an electric motor. Plus, it would be kinda pointless at lower speeds. bluemax_1 made a great post on why the AWS works like it does. I'm gonna look for it, or have him post it up again.


Would performance be better around turns when deleted the AWS all together.

Depends what you mean by better.

[Atrosity]

Road course/Handling. My 4WS light is always on...kinda wanna yank it out but it sucks to lower the subframe...

[Jimvr4]

I love this vid because it shows a cool feature in operation. Makes me want to keep all the original "stuff" working as it should

[Blurr]

@Atrosity - I would keep it connected and repair it. I haven't had enough experience with one deleted vs undeleted but from everything I gather from knowledgeable individuals, even though it's speed dependent, having AWS is a benefit in road racing.

I'm keeping mine for sure.

[MADMarc]

@Atrosity - I would keep it connected and repair it. I haven't had enough experience with one deleted vs undeleted but from everything I gather from knowledgeable individuals, even though it's speed dependent, having AWS is a benefit in road racing.

I'm keeping mine for sure.

Eric, just make sure you haul a$$ through the entire track to keep it running :D

[Atrosity]

Watch me leak all my Power Steering and I fly right into the wall....LOL...

[ahkenaden]

OK, so now that I've seen it in action, I kinda want to keep mine. However, as the mount points on the rear control arms for the rack are broken and I have no clue if the system still works, is it really worth the effort to repair?

[mh3kgt]

I thought that the 4ws light coming on means you are low on power steering fluid? Is your AWS leaking?

[Atrosity]

I don't know if mine is...I should check the power steering fluid

[DocWalt]

Make sure the little float inside isn't stuck. That can make it read low too.

[arthur92710]

How would an out of phase system work? Would this one be "reversible"?

[DocWalt]

Out of phase would mean the rear wheels steer opposite of the front wheels. I guess you could reverse the two pressure lines to make it out of phase, but the car would handle really oddly.

[91STT]

Would performance be better around turns when deleted the AWS all together.

Depends what you mean by better and what you desire.
Since it is in phase, you get a little more understeer.
Deleting it will take some of the understeer away.

[ChargerX3]

I remember that thread. I see my vids didnt carry over. :(

[DocWalt]

Feel free to post them dude, I'm just reposting useful crap I had posted :p

[ChargerX3]

Nah, Ill save us from any drama that might ensue...lol.

[bluemax_1]

We're all aware that the rear wheels only turn 1.5 degrees at most. This is a very small amount. It is NOT there to alter the steering angle, what is IS there for is to induce slip angle in the rear tires as quickly as slip angle is induced in the fronts.

If you aren't clear on what slip angle is, it is the angle of deviation between the path the vehicle is traveling and the path the tires are aimed at. To understand why this is important, you need to realize that making a car turn can be broken down into several different and distinct 'components'.

The first component is turning the wheel. In a normal car, this makes the front wheels turn.

The 2nd component is that a slip angle is induced in the FRONT tires. The car WAS going straight, but now you've turned the wheel and the tires are now aimed at a different direction than the car's momentum. This is called a slip angle. In effect, you can think of it now as the rubber being stretched because the car's momentum is headed one way, but the tires are now trying to roll another way.

The 3rd part is when the slip angle generates cornering force and the car actually physically begins to turn.

All 3 parts happen consecutively. They happen fast, but they DO occur consecutively (meaning one AFTER the other for those who might confuse consecutively and concurrently).

On a normal car without AWS though, The rear wheels DON'T begin to develop cornering force until the car begins turning and the rear wheels finally begin to aim in a different direction than the original momentum of the car. In other words, the rear wheels lag behind the fronts in generating slip angle and therefore in generating cornering force.

What the AWS does is to make the rears turn when the fronts are turned with enough pressure in the system. This means the rear wheels turn and induce a slip angle in the tires almost as fast as the fronts do and the rears contribute cornering force much sooner than on a normal car. The EFFECT of this is mostly in turn-in. When you're going straight, you turn hard into a corner, the car practically DIVES into the corner because all 4 tires generate slip angle and cornering force very quickly. Mid-corner, the effect of AWS is not that much. Th grip you feel mid-corner and accelerating out of the corner is the AWD, not AWS. Most AWD cars feel this stable mid-corner.

The difference though is what happens if you turn the wheel fast.




In the example quoted above, when you felt the rear end get loose, you counter steered fast to stop the car from skidding out. The SPEED at which you turned the wheel though, generated enough pressure in the AWS hydraulics causing the rear wheels to turn in the opposite direction as well. That coupled with the AWD traction of the car (which means the front wheels can and will pull the car in the direction you steer causes the car to WHIP around VERY quickly.

It's not about hand speed. It's about the reaction of the car. As I mentioned in my first post, BECAUSE of the AWS, these cars react MUCH faster to counter steering than a RWD or FWD car, and faster than most other AWD cars I've ever driven.

Folks who are new to the 3/S and AWS NEED to find and empty parking lot to find this out safely for themselves. You need to correct less to counter a skid than you would with another car because overcorrecting WILL make the car whip around in the opposite direction much faster than you would expect if you're used to correcting normal cars.

Before I fully understood how the AWS worked, I'd still noticed it in one particular series of turns at my regular roadcourse.

There's a long right-hander followed by a tight left-hander.

I can dive into the right-hander and hold it hard and then when I exit the right-hander, the transition from turning right to turning left happens MUCH faster than most other cars. I can take a line due to this that most other cars can't take. Going from hard right to hard left, the car suddenly changes direction, I can get on the gas hard and accelerate into the left very early and very hard. I've seen how much difference this particular couple of turns can make in catching 911 Turbo's (which are AWD), Vipers, Corvettes etc. on the track. They need to take a more conservative line AND approach to acceleration because they can't transition as fast as the 3/S and start accelerating as hard or early.


Max

Here's one of my posts about the Mitsu 3/S same phase AWS


Max

[DocWalt]

Nah, Ill save us from any drama that might ensue...lol.

Cause nobody could see them steering? :p I have a feeling with load on it, they don't look like they're turning very much... Did you ever figure out a way to mount the camera on the trailing arm or w/e to try getting a shot that way? I'm really curious if it's actually noticeable while driving, but I don't have any way to mount a camera to the side of my car and try it.


Here's one of my posts about the Mitsu 3/S same phase AWS


Max

Yep, that's the one I was thinking of. Slip angles and all... It really shows how much engineering went into this car. Maybe too much :D

[DocWalt]

chargerx3's vid :p


http://www.youtube.com/watch?v=dniEs6DsBaM

[ChargerX3]

Cause nobody could see them steering? :p I have a feeling with load on it, they don't look like they're turning very much... Did you ever figure out a way to mount the camera on the trailing arm or w/e to try getting a shot that way? I'm really curious if it's actually noticeable while driving, but I don't have any way to mount a camera to the side of my car and try it.



Yep, that's the one I was thinking of. Slip angles and all... It really shows how much engineering went into this car. Maybe too much :D

Never got a chance to try it again. I did get a new bracket to mount the camera, but as of right now my car is 2 states away with snowy weather fast approaching :(

[Atrosity]

How do you video tape like that?

[ChargerX3]

Suction mount + small camera.

[DocWalt]

Never got a chance to try it again. I did get a new bracket to mount the camera, but as of right now my car is 2 states away with snowy weather fast approaching :(

aww :( What kind of mount did you get? I have a small digi-cam, but only a tripod. I'm not going to tape it to the suspension, lol

[ChargerX3]

I picked up this...
http://t3.gstatic.com/images?q=tbn:ANd9GcTODsc4gfzCw3mZ4UZhLxwXH7dRYVBxZ RkbYXp7LYXT02Say6M&t=1&usg=__tpBKwwwZZUg3ic__Vjy7D_7g_vY=

Should be able to clip directly to the lower arm. If not im thinking a big magnet.

[DocWalt]

Hmm. If not the lower, the upper has a nice lip on it too. I'll keep an eye out.

[toddrs93]

Nevermind the AWS, what kind of shoes were they?

[DocWalt]

Which video?

[toddrs93]

the first one where he steps out at the very end

[Chris]

I love this vid because it shows a cool feature in operation. Makes me want to keep all the original "stuff" working as it should

Same here.

[DocWalt]

the first one where he steps out at the very end

Do you not see the big "POTENZA" on the tire? :p They're Nike.. uh... Yep, definitely Nikes of some sort :lol: They were leather though, and they made my feet hot all the time. F' that.