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

[Error404]

hey dude, yes its all down to how the system responds to demand from steering input. When you turn the wheel you want the steering to react as quickly as possible (there will always be some lag due to the various linkages connecting the steering wheel to the road wheels).
When you turn the wheel, the rotary valve in the rack opens ports which direct the pressurised fluid to where it is needed to assist driving the rack. The instantaneous pressure available when you make a demand from the rack is what effects how quickly it responds to steering input. If you reduce the pump flow output, you are able to maintain the instantaneous pressure available to the rack (to a point). As the rotary valve opens the pump then has to supply fluid in order to maintain that pressure, the speed at which the pump supplies fluid to do this is what effects the amount of assist and requires an increase in steering effort.

If you use a pressure relief valve to reduce the baseline pressure of the system so that it requires the same level of steering effort as above, you will also lower / cap the instantaneous pressure available when you make a steering input, so the response rate from the rack is slower which creates a laggy feeling to steering input. Of course, reducing the flow rate of the pump will also have this net result as you continue to reduce flow to a point where the system cannot build pressure between steering inputs, but by this point the system is offering next to zero assist anyway. So within reason when reducing flow rate, the instantaneous pressure remains linear. What happens when the flow rate drops too low is the pump cannot supply enough fluid to keep up with demand, consequently you experience "pump catch" where you run out of assistance following quick steering inputs (not useful when you are swerving across the road to run over a pigeon etc).

The reason the uprated torsion bar is the best solution to increase steering effort is that the flow and baseline pressure remain the same, it is the rate at which the rotary valve opens in relation to steering effort which alters i.e. you have to turn the wheel harder to achieve the same response as standard.

I would imagine Audi engineered the single stage pumps to have approximately the same flow rate as the dual pumps, so I would think you will notice no change to the steering.

HTH

[slater]

thanks for taking the time to explain, that helps a lot!

peter

[Error404]

Ok I have been talking to the guys about this and I'm looking at a batch of 8-10 units.

Price is looking at £580 each delivered for a fully rebuilt and re-valved rack with up-rated torsion bar, based on a good working rack being supplied. This could come down by a fair chunk if it is possible to avoid the full **** rape customs duty and/or find a cheaper shipping method, I'm looking into this now.

If you are interested please add your name below:

[slater]

thanks error. the outfit doing the work is in the states, right? how much would the price be affected for delivery to canada instead of the UK?

thanks!

peter

[Jamo]

Slater I think the question is more likely can they be shipped individually however if Error is taking the time to do this in a group buy all the racks will be shipped to him in bulk which is how it usually works and from there it will be distributed to the buyers.

[Error404]

I'm sure something could be sorted out

[slater]

that's what i like to hear.

am i assuming correctly that as the numbers increase, the price would decrease? i will see if i can get some more UrS brethren interested...

peter

[Error404]

Hi Peter, to be honest the price won't change that much as the bulk of the cost is labour in doing it, its quite a complex and time consuming job to fit the T-bar in the pinion, not just a case of chuck some bar in a CNC lathe

[slater]

understood...

i put a feeler out yesterday in the north american UrS community, so far about 5-6 interested parties, but everyone wants to know what it will cost delivered to their doors. any chance you can inquire about that? this would be US and canadian deliveries.

thanks!

peter

[Error404]

I will get all that info Peter. Please do note that the rough pricing I have is based on the work we have done on the B3/B4 platform rack. I assume it will be very similar in the C-platform cars but I don't know until I can get my hands one one to look at.

[slater]

hi error,

did you ever hear back on a cost and shipment details for north american customers?

thanks!

peter

[Skull]

1. do we have to provide an s2 rack, or are other b4 racks also ok?
2. can the rack be made quicker and if yes how much £ for it?
3. it this for both RHD and LHD racks?

[Error404]

Hi guys,

No TBH I didn't do anything yet due to lack of interest and I don't want to waste their time as they are very busy.
My adjustable PAS pump prototype is almost ready though.

Rok:

1. Yes you would supply a rack, s2 or B4 are OK the T-bar is the same.
2. Yes it is possible but you can already just buy a stock ABY/ADU rack which is 2.6 turns, or for a quicker rack 034 sell a 2.2 turn rack, Selholm do one too so there is no market for it.
3. I have not inspected a LHD rack but i imagine it is a mirror image so 99.9% yes.

[butchone]

im in please if a 1986 coupe quattro rack can be made as quick as possible? (for competition)