[urq] [s-cars] S-Car Brake system conversion- Read- no more PSpumpintegration <question>

[urq]

I believe some manufacturers have an electric vacuum pump in the system ...
a friend of mine had an old Celica Supra Turbo and that is what it used for
ensuring brake boost was available.  You'd need to have some idea of how
much capacity was needed per brake application, and how many applications
per minute to scope the pump flow rate.  

Another option would be to add vacuum reservoirs to the system.

Steve B
San Jose, CA (USA)

-----Original Message-----

Interesting but not surprising. I wonder if something could be done on the
order of the old 4kq assist pump (maybe additional electric-driven vacuum
pump). The 4kq system, for those that recall, had a vacuum assist pump
driven by the camshaft. Not doable directly, of course. But that's
essentially what you need -- a vacuum assist helper. 


Ingo Rautenberg

-----Original Message-----


I have an UR S6 with brake issues as well, so I can empathize with those
feelings! My car is briefly activating the anti-locks on every stop as the
speedo crosses 10 MPH on decel.
In the FWIW department, I have switched my URQ over to the vacuum system
from a CGT, and it works fine for daily driver duty. However, I have tracked
the car twice since and found that 4 laps on a small tight course is all I
get from the vacuum system. In the? fifth lap on both courses the brakes
went rock hard.?Still functional enough to keep me out of trouble, but the
assist was gone. Pulled into the pits and let it set for a few minutes and
all went back to normal. Four more laps and repeat.
In the past when I have tracked a car with regular brake fluid (not
SuprBlue) I have encountered boiling brake fluid which required a much
longer recovery time, and felt much more disconcerting on use. The brakes
would almost go away completely.
I'm definitely not suggesting you take either option and modify your brakes
in any way. That is totally your responsibility, but thought this
information might be of interest.?


Dennis Graber
Denver, CO


-----Original Message-----

Without GOOD engineering a vacuum assisted system is not exactly a good idea

on a turbocharged car which is exactly why Audi went to hydraulic brake 
boosters anyways. The '95 A6 system would likely not be suitable. It could 
likely be made to work, but I don't think it's worth the risk of a failure 
at the wrong time. The modern cars use a venturi vacuum pump to create 
vacuum for the brakes even when on boost, but these venturi's fail (get 
clogged) on a somewhat regular basis.

-Cody Forbes

brian bilotti wrote:
> S-Heads,
>
> Anybody done this conversion? I'm sick of having brake issues with
> the PS pump. My mechanic says that the A6 has a vac assisted set up
> that eliminates the need for PS pump integration.
>
> The need for some off the shelf parts and a check valve is all I
> need.... I'm told.
>
> ANY info would be great!
>
> Thanks
>
> Brian