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  #16  
Old 07-25-2008, 04:26 PM
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Quote:
Originally Posted by JimmyL View Post
$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?
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  #17  
Old 07-25-2008, 04:32 PM
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Originally Posted by zeke View Post
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.
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  #18  
Old 07-25-2008, 05:27 PM
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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.
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Last edited by pwogaman; 07-25-2008 at 05:45 PM.
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  #19  
Old 07-25-2008, 05:30 PM
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Quote:
Originally Posted by tangofox007 View Post
Speed.
How much? 1.2 vs 2.5 = 2.1x

Does that mean you pull the vacuum for 30-min instead of and hour?
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1979 maple yellow 240D 4-speed


Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT
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  #20  
Old 07-25-2008, 05:48 PM
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Originally Posted by zeke View Post
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.
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Peach Parts W124.128 User Group.

80 280SL
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  #21  
Old 07-25-2008, 07:18 PM
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Quote:
Originally Posted by zeke View Post
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.
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  #22  
Old 07-25-2008, 07:26 PM
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Quote:
Originally Posted by Diesel911 View Post
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).
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