Hydraulic to vacuum servo conversion

[spiralsmurf]

any updates?

[A80Avant]

Im digging this thread up as there is a high chance of me converting to a vaccum servo.

I am told from Marc@EFIExpress that a lot of people in the states with AAN engines have converted just because of being fed up with brake issues as well.

However im a bit puzzled with the fact of the need to change a power steering pump. I would have thought that you dont, since the steering pump is a dual vane pump and therefore if the hydraulic route to the servo is not needed, it can just be blocked.

So what needs to be done is:

Line to the bomb removed
Bomb removed
Return line from servo removed/blocked
Return line from bomb removed/blocked

and the vaccum servo will fit the OEM master cylinder,
check valve to the IM,

the only difference i can think of off the top of my head is where the power lines to the sensor of the pressure will go, as some master cylinders used to have this on them, wheras our cars have it on the hydraulic servo.

All this will possibly require the strut brace modified, and the cruise control module moved out of the way, but i think in the end, it would work much more reliably.

As for left foot braking, i have never done it, but even if i had to do it a bit on roundabouts, the vaccum servo does store vaccum as well, otherwise in case of an emergency where the engine stalls, you would always loose brake assist and that doesnt happen. It stores vacuum in the same manner as the bomb stores pressure.

any thoughts?

[A80Avant]

here is a photo of a friend's old timer audi which has been transformed with an rs2 engine.



on this master cylinder the sensor for the pressure is on it,whereas we have our sensor on the servo.

[Pirvu Eugen]

HY! You dont need to change the pump....just remove the pistons from the high pressure side and plug the hole wich goes at the bomb.
I have done this and is working since...
Hope this helps!
Now..i want to put inline an electric vacuum pump with an vacuum switch...to operate only when the vacuum is lower then 0.5 bar.
Success!

[A80Avant]

why would you do this? is there a problem with it working at all times when under vaccum?

[Pirvu Eugen]

For left foot brake.... The vacuum booster will loose the vacuum at some point iff the engine is under boost all the time. Offcourse..for normal driving...no prob without.
All the best!

[A80Avant]

thanks Pirvu!

do you happen to have any photos of the brake servo to use as a guide roughly??

thanks

[quattrofrank]

I`m thinking about doing the same to my s2. But I want to get rid of the power steering pump completely.. I guess I need to get at steering rack from a 80/90 without power steering. Does anybody know if that was an option, or is power steering standard equipment?

[Pirvu Eugen]

You can use an electric one...from A class...
There are steering racks without assistance.
About the brakes... i was thinking at 1 point to install an alternator from Opel Diesel wich has a vacuum pump built in...but it needs oil feed and return...and i dont want to mess with engine oil.
Regards!

[quattrofrank]

The a-class electric one, is this sufficent for the steering rack? If I remember correctly it needs 100bar working pressure ?

[Pirvu Eugen]

It is! I have that on my car...

[A80Avant]

pics please!!!!

[martinws]

Im going to be putting an ABY in my typ85 90 soon and i will just be hooking up the vacuum line to the IM with a check valve and see how it goes. If it doesnt suffice then ill probably get a diesel alternator with the vacuum pump onboard and put that in.

[quattrostyle]

I`m thinking about doing the same to my s2. But I want to get rid of the power steering pump completely.. I guess I need to get at steering rack from a 80/90 without power steering. Does anybody know if that was an option, or is power steering standard equipment?

type 89 80's came without power steering, well some of them. How fast would you need one as my brother will change his for a power steered one.

[quattro84]

I am looking for a complete set with a controller such as this:


I don't want to mess around with electronics, preferably a controller which uses vehicle speed as an input.