hydro vs vac

[A80Avant]

its special in the way its constructed. Its not a plain pressure pipe. Apparently it has an inner metal tube with a restrictor made specialy to avoid this noise and vibration...

[S2central.net]

I found this pic in another thread... look at top of A-pillar and you will see location of vac reservoir on S2/RS2

http://i244.photobucket.com/albums/gg8/christofferjohnsen/CIMG7144.jpg

[V6quattro]

Yes that's the one I've seen on my car. I don't think there is another one on the Avant.

[Error404]

its special in the way its constructed. Its not a plain pressure pipe. Apparently it has an inner metal tube with a restrictor made specialy to avoid this noise and vibration...

There is no restrictor in the line, but there is a perforated inner tube - that's there to dampen the noise of the pump, kinda like how a straight through exhaust muffler works.
Proper PAS hose will have this in, most hose places just use stock hydraulic hose which works fine but you end up with the whine when turning the wheel.

[A80Avant]

so at least the whine is not something that is damaging to the pump or the rack...

[Error404]

likely no, but i guess it depends how they have done it and what spec pipe etc they have used

FYI the pump pressure is circa 140bar

[A80Avant]

pump pressure for the steering should be below 100bar. 140 is for the brake side. They used a proper spec braided hose at the same diameter as the original hose and they inserted the plastic tube as well. Dont know, only need to do about 150miles to leave the car at the next garage, so i hope its not going to cause any more problems..

[prj]

Voted hydro bomb, just because it sounds like it'll make a bigger bang

[Pirvu Eugen]

Because i was at the point where i need to fabricate the hose from the power steering at the rally replica i have here... I made some pictures with diferent hoses, from diferent cars.....but from the pump to the steering rack.
First picture shows 3 hoses....from the left to right...Audi V8 complete hose, next is same hose but split in 2 from the middle conection and you can see the inner plastic tube wich is 6mm outside diameter and 3.5mm inner...this is the vibration damper and the last is the audi coupe gt oem hose.
The second picture is with the plastic inner tube from the V8 hose.
The third picture is with the gt hose and with the position off the restrictor inside.
The differences between the plastic tube and restrictor is because the V8 uses an tandem pistons pump and the gt (same as S2) ( for the power steering at least), is vane type pump.
Where pistons are used.... inner tube is used....
At the vane pumps... short restrictor at the middle....
Hope this helps!
Regards!
Eugen

[Pirvu Eugen]

I used the coupe gt hose in 3 cars with modified S2 pump till now without noises.
Iff you open the hose from the pump to the bomb....the one wich receives the pressure from pistons....you will see that inside..has a small plastic tube....same as the V8 hose..but less diameter...
The vibration caused by the pistons is higher then the vanes...from this..the differences in design.

[A80Avant]

hi pirvu,
is it possible to send those photos on my email a bit larger? they are quite small and cannot see them very well
thanks

[A80Avant]

im wondering if all the people who vote for the hydro assist have ever had an expensive failure, or if they just left foot brake all the time!!!

[Pirvu Eugen]

I was thinking at this also...
Is interesting.....
i will never go back to hydro..ever...
BTW...is there..any new gasoline turbocharged car with hydraulic brake assist?
Dont think....

[Billman]

What does the TT has?

[A80Avant]

Which TT? All previous ones have vaccum.
I haven't seen a TTRS up close to tell, but even the new TTs 2.0T have vaccum
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