Problem with Diravi System, Diravi steering no return to center

[jef360]

Diravi steering is not returning automatically to the center.
Does anyone know what might be happening?
Automatically return to the center is the charm of diravi.

Thanks!

[robertmnorton]

Hi jef360, I've never had a DIRAVI equipped car but have studied the system generally out of interest. You've only mentioned the centering, which is dependent on the hydraulic pressure. This is determined by the DIRAVI regulator which is controlled by a cable drive from the g/box, the greater the pressure the greater the centering force.
robertm

[jef360]

Hi robertm,

Currently I am studying Diravi steering to try understand this problem. I think that Diravi system is very interesting. Currently I am restoring my XM and I want to make it new.

In the photo attached have highlighted a cable, this cable is that controls hydraulic pressure to generate returns to the center?
I was informed that I can try to pour oil on the outputs of Diravi to try to remove air that may be in it, what do you think?
Thanks for answering!

[kenhall1202]

Hi jef360,

You might find the following link helpful in understanding the operation of (early CX type) DIRAVI power steering

http://club-xm.com/forum/index.php?showtopic=4124&st=20

Note that the DIRAVI design changed between the CX and the XM and the separate governor may have been incorporated into the main control unit.

The DIRAVI equipped XMs have an adjustment feature under the bonnet (near the LHM tank I think) for centring the steering. That may be what your photo arrow is pointing to. Earlier DIRAVI equipped CXs did not have this feature and centring adjustment was done mechanically on the rack coupling.

Ken

This post has been edited by kenhall1202 on April 29, 2013 09:32 am

[noz]

Hi Jef,

I have not had any experience of the DIRAVI for the XM because DIRAVI was never available on Right Hand Drive cars. However, I have indeed stripped down a DIRAVI unit from a CX which was causing me some trouble. The self-centering cam can be seen on the image in the post to which Ken gave the link. It is called the "Return Cam". You can see above it there is a piston pushing on a roller which in turn pushes on the cam. The cam only has one low position and that is with the steering pointing dead ahead. At all other points the cam profile is higher therefore the piston has a tendency to push on the cam and rotate it back until the low part of the cam is aligned with the piston. The amount of pressure pushing on this piston depends on the speed of the car. At low speeds the pressure is low and at high speeds the pressure is high. This makes the steerring very easy at low speeds and very stiff at high speeds. In the CX the pressure is governed by a separate device located on the right hand inner wing (on RHD cars). It has some centrifugal weights and a slide valve (exactly like a Watt steam governor). The slide valve controls the amount of pressure allowed to pass from the hydraulic pump to the piston in the DIRAVI column. The weights are spun around by a second speedometer cable coming from the same outlet on the gearbox as the drive for the speedo on the dash (instrument panel). There is a small plastic gearbox plugged into the main gearbox with two outlets which are geared with different ratios. One drives the speedometer and the other drives the steering governor. In both cases there is a cable running from the plastic gearbox to the other device. The cable has an outer shell and the inner braided cable rotates within it.

It looks like the XM has the governor built into the Rack rather than separately as in the CX. The arrow in the photograph looks like it is pointing to the cable I mentioned above. Firstly, you need to determine if the inner cable is rotating or if it is seized. Next, you need to determine if the drive end of the cable is working. I have suspected that the speed sensor fitted to the 2,5TD has a second outlet which is currently plugged. I thought that this might be the drive for the governor cable. It looks like it may be. Occasionally, if the cable seizes then the teeth on the gearwheels inside the plastic gearbox will be damaged. If this is the case, please make sure the inner cable can turn freely before replacing the plastic gearbox or the same thing will happen to your replacement.

I hope that has given you some food for thought.

cheers

noz

[kenhall1202]

QUOTE (kenhall1202 @ April 29, 2013 09:26 am) 

Hi jef360,



Note that the DIRAVI design changed between the CX and the XM and the separate governor may have been incorporated into the main control unit.

Ken

I was mistaken as the following underbonnet view of Caique Macedo's Brazilian V6 XM will show.
The knurled knob for adjusting the steering centre position is in the far right of the frame (below the red label) and the centrifugal governor is the round black plastic object near the top left of the frame.

Ken

This post has been edited by kenhall1202 on April 29, 2013 06:57 pm

[jef360]

Hi people,
Very thank by yours posts.
Now, I will analyze your posts to try understanding and passing this information to mechanic.
Hi Ken, I am from Brazilian too, have you contact's Caique Macedo?

When I finish this troubleshooting I will send an answer for yours.
Thank!

[kenhall1202]

Hi jef360,

Caique Macedo's details here: http://club-xm.com/forum/index.php?showuser=1347

I see his last post was in late 2009 so I have a feeling that he no longer has his V6 XM.

Ken