$75+ shipping Air Conditioning Vacuum Pump - Page 2 - PeachParts Mercedes-Benz Forum

zeke · #16 07-25-2008, 04:26 PM

Quote:

Originally Posted by JimmyL

$15 bucks more gives you a 2.5 vs that 1.2

But is it worth it?

http://www.redhillsupply.com/auto-ac-vacuum-pump-1.htm
Based on info from this site, 1.2CFM is adequate for auto work, but the 2.5 is not enough for residential work.

So what is the advantage?

tangofox007 · #17 07-25-2008, 04:32 PM

Quote:

Originally Posted by zeke

But is it worth it?

http://www.redhillsupply.com/auto-ac-vacuum-pump-1.htm
Based on info from this site, 1.2CFM is adequate for auto work, but the 2.5 is not enough for residential work.

So what is the advantage?

Speed. But in the case of a car, we are talking about seconds.

pwogaman · #18 07-25-2008, 05:27 PM

Less time to boil out the moisture from your system. If you pull a deep enough and long enough vacuum you can even pull the moisture out of the receiver dryer.

zeke · #19 07-25-2008, 05:30 PM

Quote:

Originally Posted by tangofox007

Speed.

How much? 1.2 vs 2.5 = 2.1x

Does that mean you pull the vacuum for 30-min instead of and hour?

pwogaman · #20 07-25-2008, 05:48 PM

Quote:

Originally Posted by zeke

How much? 1.2 vs 2.5 = 2.1x

Does that mean you pull the vacuum for 30-min instead of and hour?

I pull for at least an hour. With 1.5 cfm you would need to pull 10x as long to get the same, not considering the Hg difference.

tangofox007 · #21 07-25-2008, 07:18 PM

Quote:

Originally Posted by zeke

How much? 1.2 vs 2.5 = 2.1x

Does that mean you pull the vacuum for 30-min instead of and hour?

No. It just means that you will get to the minimum pressure faster. On a car, the time difference is not significant. The volume of air in the system is relatively small.

pwogaman · #22 07-25-2008, 07:26 PM

Quote:

Originally Posted by Diesel911

You are right; when we see let us say a pressure guage and look at Zero on the guage we do not account for the Atmospheric Pressure. Sometimes I have seen pressure listed ad "psig" instead of "psi" meaning the pressure as read on the guage.
Anyway you answered my question the pump pulls enough vacuum to do the job.

PSIA is pounds per square inch absolute (like in outerspace)
PSIG is pounds per square inch guage (zero is set to at whatever elevation you happen to be; if it is not adjustible then it would generally be set to zero at sea level).

PSI is just pounds per square inch within the measured medium without reference to the surrounding pressure (or lack thereof).