Lubricant for steering? (Potential solutions for Mirage's lack of self-centering)

[ThreePot]

Now that foama (Post #30) has shown that the lack of self centering is due to the electric power steering assembly, the question is "How"? I can't envision how the power assist can cause this characteristic.

This assembly is from a 2014 ES
Now I can think about this without taking my car apart....


When I push on the motor can, and rotate the unit around the shaft, there is a mild/fair amount of drag (several inch pounds) as the shaft back drives the motor armature through the worm gears.

Any drag on the shaft is going to mess with the road feel around center on such a light car.(?)
Since the torque sensors are on the steering wheel side of the motor, I'm suspecting the system is not so good at compensating for the inherent drag. (pure speculation)

Assuming that removing the motor would eliminate any drag....(havn't tried it yet)
I want to see how the car would feel if I removed the motor so there was no drag, and drove it as a pure rack and pinion.
I have to look at the manual and see how that motor comes out. I don't want to remove it if it cant go right back in.
If the motor can come out without any complications, I can pop it out, hang it off to the side, pull the EPS fuse and go for a quick drive. ???
Then I'll know for sure.

The only way to know just what that EPS does or doesnt do is to eliminate it (and its residual drag) and see how the car drives. imho, Anything else is just guessing.

[MiMi]

Good work in defining the problem.

[ThreePot]

I removed the motor. It does come right off, no drama.
The worm gear set is still turning with the motor removed.
There is still drag, the motor has a short splined shaft that engages the end of the worm gear.
The motor shaft itself has some resistance, but not as much as I had guessed it would.
The worm gear set adds a lot of the drag.
So...I can't readily do my steering feel experiment on the car.

Next step would be to take apart the assembly to remove the worm gear set.
I gotta think about this some more.
I was wondering if one could put a DVM on the motor power lead and use it just to be able to see when exactly the EPS is providing any kind of assistance while driving....Hmmm.

[m4v3r1ck]

Have u managed to disassemble everything and tried pure rack and pinion driving?

[MetroMPG]

ThreePot - above and beyond the call of duty! Thanks for posting the details.

[M-88]

So it's a manual rack with electric assist on the steering shaft?

I guess I pictured electric steering racks to work a lot different.

If that's the case - it should be able to function without the electric part (even if unplugged). My concern would have been extra strain on the steering shaft.

[Daox]

Very cool ThreePot! Thanks for sharing your exploration of Mirage innards.

[ThreePot]

Have u managed to disassemble everything and tried pure rack and pinion driving?

I have not gone further.
I hoped that I could eliminate all the drag by just removing the motor.
If that was all it took, I could try removing the motor from the unit in my car, and take it for a drive.
As it turned out, to do my "pure rack and pinion" experiment I would have to swap the whole EPS unit.
I won't attempt that right now. I need to see the service manual before I decide to do it or not.

I would at least like to take the EPS unit the rest of the way apart.
I need to get a couple of sockets (deep 27mm, 40mm) to continue.

[ThreePot]

So it's a manual rack with electric assist on the steering shaft?

I guess I pictured electric steering racks to work a lot different.

If that's the case - it should be able to function without the electric part (even if unplugged). My concern would have been extra strain on the steering shaft.

When I kill the power while coasting, the car is not easy to turn. (many have tried this, I'm sure)
So, it definitely function

I bet the EPS unit is designed to keep steering even though the electric part has failed (?)
So, I suspect the shaft can handle the extra strain (?)
I'm still curious to see the rest of the internal parts.

[ThreePot]

Thanks for all the kind words