Sport Steering Rack

[slater]

Yeah I experimented with a couple different valve setups, they do have an effect but at a cost. All this valve does is throttle back the baseline pressure at the rack so the steering becomes super laggy and you have next to zero assist at parking speeds.
A flow control valve is a better way of doing it but it puts massive strain on the pump, you are better off making the pumps internal flow control valve adjustable, which I have already worked out how to do, just waiting on the prototype to test

Changing the torsion bar is the proper OEM way of doing it

can you elaborate on why it would make the steering feel laggy?

i am actually changing to a single-chamber PS pump from a V6 as i am doing a vacuum-assist conversion for the brakes.

peter

[Mcstiff]

Makes sense, I figured there was a downside! Staying tuned for info on both mods

[Error404]

Yeah I experimented with a couple different valve setups, they do have an effect but at a cost. All this valve does is throttle back the baseline pressure at the rack so the steering becomes super laggy and you have next to zero assist at parking speeds.
A flow control valve is a better way of doing it but it puts massive strain on the pump, you are better off making the pumps internal flow control valve adjustable, which I have already worked out how to do, just waiting on the prototype to test

Changing the torsion bar is the proper OEM way of doing it

[Mcstiff]

Any thoughts on this valve? http://m.summitracing.com/parts/HDT-PS-101

[Error404]

fascinating thread guys, good work.

i am in canada and have a '96 S6, and would be interested in potentially getting the same treatment done to a spare UrS ZF rack that i've got.

Error404, i would also be interested to hear more about your flow control valve (on pg2), and whether you will be producing them?

keep up the good work!

peter

Hi Peter,

Yes the flow control to the PAS pump is a fairly simple mod that involves some machining to the pump itself. I am waiting for a prototype to be machined still, I'm sure it will be possible to do the same thing to a UrS pump. Likewise with the rack mod..

[slater]

fascinating thread guys, good work.

i am in canada and have a '96 S6, and would be interested in potentially getting the same treatment done to a spare UrS ZF rack that i've got.

Error404, i would also be interested to hear more about your flow control valve (on pg2), and whether you will be producing them?

keep up the good work!

peter

[willg54]

the counties supply of spare ABY/RS2 racks will soon disappear

[Error404]

it will work on any rack but the initial group buy will be ABY/RS2 racks

[tscheel]

I have a load more testing to do, but I will be talking to the firm in the states about getting some more done in due course.
I need to do some miles on it and also would like to test it on track.

I know of a couple of people who have already expressed an interest, but f anyone else is potentially interested please get in touch or start a provisional list on this thread, that will help to give me a rough idea to generate some costs.

I need to chase Kev regarding the PAS pump prototype too, but I know he has been super busy!

Cheers
Alex

Interested. Have I understood correct that you estimate the cost including shipping to around 500£ ?

Is it possible to use a rack from a standard Audi 80 for modification, or does it have to be from S2?

[Mr.Crossfire]

About the model, it's rough and ugly, but the geometry should be about correct. Some screenshots. The model shows me camber, caster, SAI, instant center, roll center, height position of suspension and steering angle. All of those don't show in those pics, as it is viewed straight from the rear. It does not automatically draw any plots or curves, I have to make those manually with excel.

About the caster modification, it looks like this. The camber/caster plates are of my own design, and made by me. Only the uniball and the cup for it were bought from a local rally/motorsport shop. There's a model of those plates.

E: I don't know exactly where is the turning point from positive to negative gain, but I can investigate it with the model when I get back home.

[Error404]

Yes I'm sure it will be fine

You have done some very interesting work
Do you have any more info & pics on the modifications you made to the strut tower and your modelling of the suspension geometry?
Do you know what kind of castor angle is required to remove the positive camber gain on compression?
I guess you cut the top off the strut tower and welded in a flat plate to use the more common adjustable topmounts ?

[Mr.Crossfire]

The KW's have the same length arms as oe struts, but the arms are few cm lower.

Yes, killing the positive camber gain was the main reason to do the caster-mod. I have made a 3d-model of the front axle of a t89-chassis. I simulated the camber gain with it, and got quite encouraging results with the modified caster angle. With increased castor, you get a little negative camber gain during the compression of suspension & when wheels are turned. Opposed to the stock geometry, where the gain is positive. If the control arm angle is altered also, it will result even steeper negative gain.

But yes, the stock steering is still too light. What do you think, is it possible to participate on the group buy from Finland? I'd need to source a spare rack though and also some cash...

[Error404]

Having had a quick look over the last few days, the effective length may be marginally shorter - the arms are the same length, but the strut body is a smaller diameter, so the distance from the track rod ball joint mounting hole to the strut axis might be ~ 5mm shorter on the KWs

[Mcstiff]

what do you mean about the KWs dude? I know the steering arms are lower, but still the same length I think
Regardless, the motion of the rack remains unchanged with this upgrade, only effect is that the steering is firmer and feels much more direct

I was under the impression they had shorter arms.

[Error404]

That's really interesting as I am planning to try adding some more castor, to achieve around 4 degrees total to try to increase the self-centring effect and improve turn-in / reduce dynamic camber gain. I think it is unrealistic to expect huge amounts of steering feel given the design of the steering system on these cars, but I think reduced assistance from the rack as well as some additional castor and a touch more negative camber will be about the best without going totally custom on the steering rack & column set-up
FYI my car now feels more like an S5 than an S2