Re: Vacuum Pump Settings?

[Leon Levasseur <leon@ziplink.net>]

At 01:47 PM 1/30/99 Saturday, you wrote:
>     Since I'm rigging up a vacuum pump and power brakes on the truck, I've
>run into a couple of questions -
>
>     What should I set the vacuum switch to?
>     Would anyone recommend using a reservoir?
>     If a reservoir, approximately what size?
>
Hi Mitch;
 Most ICE engines rarely produce more than 19 to 20 inches of vacuum.  With
that as a starting point you would not overstress any other components that
may
use vacuum to operate, such as the guts under the dash for ventilation
etc..  I
doubt running a higher vacuum will do any physical damage as your only looking
at a 5# increase if you went to may vacuum at 27 or 28 inches.
 You may want to consider the efficiency of the pump when going beyond the 19
in.  Measure the time it takes to produce greater vacuum and you can calculate
the drop in efficiency at a higher vacuum if any.
 Use a 3 or 4 inch schedule 40 PVC pipe about 24 to 30 inches long for a
reservoir.  End caps are available, which makes an excellent corrosion
resistant tank.  The wall thickness is sufficient to allow for threading a 1/8
to 1/4 inch pipe tap for fittings.
 I run my vacuum at around 25 to 26 inches and can cycle the brake pedal 5
to 6
times with a drop from 25 to 8 inches with the pump off.  A gauge and or
preferably a warning device to alert you when and if the vacuum drops below a
set point is a good safety feature.
 My unit will evacuate a 4 x 24 tank from 0 to 25 inches in about 6 seconds
running the Kostov at about 200 rpm.  I use an A/C compressor as a vacuum
pump.
 
Best regards,

Leon