Adjustable Steering Assistance Kit

[Le S2 Audi]

its 5/112 pcd, just cant remember the offset, et47 from memory so its going to be more inboard than a stock s2 wheel (not sure what the s6 offset/ET is)

Its not in great condition i dont think, to be honest i havent seen it in the garage for months

Hummm too Much Christmas Cheer Me Finks !!!!

[Error404]

Finally managed to get a few hours on this little project to build a prototype setup.
I've rebuilt a stock pressue hose keeping the funky OEM hose ends, cut the hose in half and added fittings to plumb the valve in line.



The standard hose does not have any kind of magical valve in it as is mythically believed.
The hose contains a perforated nylon hose liner that is supposed to reduce vibration and noise.

Hopefully I'll have time to fit and test this tomorrow.

[Rusty]

Looking forward to this in conjunction with 'projekt kamber' Just the top mounts to go and we might have something resembling a sensible steering weight and feel!

[Error404]

heres hoping

[Mcstiff]

Interesting

[quattrofrank]

I belive most of the s2`s have servotronic originally. There`s a solenoid fitted on the steering rack. I dont know how it work but there`s only 2 pins so I guess this would be possible to adjust electronically in some way?

[Error404]

Fitted these bits today and took the car out for a quick spin. The system does work, but no miracles.
I can wind the valve out to completely eliminate all PAS assistance, or any amount in between. There is a slight bit more noise from the steering going lock to lock and at slow speeds... this might be a bit of air in the system, needs more investigation.

As you will no doubt have guessed the more the pressure is reduced, the harder the wheel is to turn at parking speeds, so there is a balance between a nice weight above 10mph and not being able to turn the wheel when stationary. Ideal weight at speed would render the car literally un-parkable. Obviously this is what Audi tried to acheive with servotronic - pity they didn't get it right.
Wish i was techie enough with electronics to have a mess about with a servotronic rack as i'm sure it could be tweaked.
This is the reason the non-servotronic steering is so light, as the car just would not have been saleable had the steering been any heavier to park.

Pleasingly steering "feel" IS increased with less assistance. You can feel the road surface more clearly through the steering wheel.
Self-centering feedback is still nonexistent.

One thing that became quite apparent with the assistance reduced was that beyond about 1/4 a turn of lock to each side, the steering weights up considerably. My theory is its due to the relationship between castor / SAI angles - very low castor so there is not much feedback from the self centring effect, once you start to lift the weight of the car due to SAI coming into effect the steering weights up more. So I guess this is why once you're in a turn the car feels much more positive, but nervous and vague in the middle of the rack.

I'm going to test this all more thoroughly and see how it plays on all different types of roads and speeds, hopefully on track too if time / cash permits.

[Error404]

Firstly forgive my ramblings!
I have been putting some though into this and doing some R&D. I gave up on the line pressure adjustment as it was really the wrong way to go about this. The PAS is a demand based system, the when the rack receioves a steering input, the rotary valve in the rack opens ports which directs fluid flow to either end of the rack, offering assistance.
The flow rate to an extent must control the amount of assistance available at the rack, since this depends on the speed at which the pressure can equalise once the rotary valve opens the ports to direct fluid to the rack. Therefore, control the fluid flow, control the speed at which the rack provides assistance. Now this is only good in limited amounts, i.e. you don't want "lag" in the steering, which will happen if there is too little flow. But i thought there would be some room for improvement over the stock system. So I switched out the pressure relief valve for a flow control valve, and guess what? I works. There is a very fine level of adjustment between not being any different to creating loads of lag in the steering, but there is a sweet spot. This doesmn't generate more road "feel" but what I call 'feedback' is far far better, i.e. the wheel tries harder to self centre and more effort is required to steer at all speeds. The car feels SO much more positive to chuck about, much more planted than with the feather light stock set-up.
Now, the way i have done this is not right, as the flow control valve is putting a lot of strain on the pump, BUT i have proved the theory. The correct way to throttle the pump flow output would be the correct spring in the PAS pump spool, something at this stage I can't be bothered to pursue, but it out there for anyone who can. Alternatively, an easier way would be a 3 port flow control valve inline with excess to tank which would reduce the back pressure on the pump, but again, not the right way to do it.

All of this has lead me to another enlightenment about how the power rack works and I am currently having a bespoke part made to fit to a modded ABY rack to see if i can sort this once and for all the way Audi should have done in the first place - it better work as my steering fanaticism stands me at a pretty considerable loss right now. Watch this space.

ramble over

[Error404]

Oh yeah i also found out the MK3 MR2 electric PAS pumps have a speed controller which takes a speed signal from the ECU to throttle back the pump as speed increases, I'm pretty sure an electrical techie could knock together a little box of tricks to make that work very nicely using the gearbox speed sensor output? Kinda like servotronic that works properly

[Rocco]

and why not to unplugg the Servo asistence? the plug under the rear bench...and it makes the steering wheel harder

[Error404]

1. its only on 3Bs
2. It just makes the steering the same as any other B3 / B4 car anyway

I'm trying to make it better than this Rocco

[Rocco]

1. its only on 3Bs
2. It just makes the steering the same as any other B3 / B4 car anyway

I'm trying to make it better than this Rocco

ok ok you won

keep us posted then

[Rusty]

Sounds like you're having fun with this Do you have a stock rack or an S2 rack?

[Error404]

I've got quite a collection at the moment Andy! Got an ABY / RS2 rack in the coupe.
then I've got another ABY one, a CQ one, and a 3B on the bench and a URq one on the way

[Mcstiff]

Oh yeah i also found out the MK3 MR2 electric PAS pumps have a speed controller which takes a speed signal from the ECU to throttle back the pump as speed increases, I'm pretty sure an electrical techie could knock together a little box of tricks to make that work very nicely using the gearbox speed sensor output? Kinda like servotronic that works properly

Depending on the signal required this would be easy to do with VEMS. Too bad I like hydro brakes.


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