Need input on my compression numbers
08-08-2002, 01:11 PM
#11
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So if it is an immediate reading it will stop leaking are once it gets to a certain point. In other words, you put 100 #'s of air into the cylinder and it leaks down to 95 #'s in a few seconds then stops leaking that would give you 5% leakage. Is this correct?
I was thinking that if things weren't sealing 100% they would continually leak down to 0 in a matter of time. Say 95 #'s after 10 seconds, 90 #'s after 2 minutes, etc, etc.
That's what I get for thinking!!!
I was thinking that if things weren't sealing 100% they would continually leak down to 0 in a matter of time. Say 95 #'s after 10 seconds, 90 #'s after 2 minutes, etc, etc.
That's what I get for thinking!!!
08-08-2002, 01:43 PM
#12
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You hook up an active airline to it. Set the regulator too 100#s and the other dial shows how many pounds the cylinder holds. It doesnt leak down to zero becuase it has air going to it. The term leakdown is kind of misleading. It actually shows how much air passes through the cylinder. Should be done on a warm engine. Hope that explains it better.
08-08-2002, 03:13 PM
#13
Gold Member
Gold Member
I thought you pressurized the cylinder to a prescribed PSI on one gage, shut off the incoming air and then monitored the pressure drop over time with the other gage.
If you have constant air pressure flowing in, how could you measure pressure loss?
If you have constant air pressure flowing in, how could you measure pressure loss?
08-08-2002, 06:28 PM
#14
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08-08-2002, 10:02 PM
#15
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Charter Member
Originally posted by Iggy
From what I read the cranking compression on a pump gas motor should be around 160-200 psi. Probably talking about a freshly rebuilt or new assembly.
For those that don't have access to a leak-down tester there's an old trick to see if the rings or valves are causing a loss of compression. First pull all the plugs, take a reading on each cylinder then squirt a small amount of oil in each cylinder, crank it over a bit to distribute the oil and recheck the compression. If you get no change in the readings, bad valves. Just the opposite, if the readings spike up then the rings are worn.
From what I read the cranking compression on a pump gas motor should be around 160-200 psi. Probably talking about a freshly rebuilt or new assembly.
For those that don't have access to a leak-down tester there's an old trick to see if the rings or valves are causing a loss of compression. First pull all the plugs, take a reading on each cylinder then squirt a small amount of oil in each cylinder, crank it over a bit to distribute the oil and recheck the compression. If you get no change in the readings, bad valves. Just the opposite, if the readings spike up then the rings are worn.
08-08-2002, 10:52 PM
#16
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Still confused
So the left gauge would be putting the regulated air in constantly. But the right gauge would actually be reading the air pressure of the cylinder. So, if your putting 100 lbs in and the cylinder will only hold 95, then you have 5%. Correct?
I was with Iggy. I thought you pressurized it, turned the air off and monitered.
Learn something new everyday!
I was with Iggy. I thought you pressurized it, turned the air off and monitered.
Learn something new everyday!
08-09-2002, 12:16 AM
#17
Platinum Member
Platinum Member
Be aware that a leakdown tester that you can buy has a metered orifice after the regulator and before the second gauge. This orifice is sized to provide a percentage of leakdown shown that corresponds to a leakdown over time test.
All of the old Clymer motorcycle manuals illustrate doing a leakdown by pressurizing and recording pressure loss over a time period and then computing the percentages. The two-gauge testers mimick this same procedure but shortcut it by giving you a direct reading. Without an orifice, though, the leakdown numbers will be ridiculously low since the regulator can supply a large flow of air before showing a significant drop in pressure.
I'm not sure of the orifice size in these units, but if somebody will take one apart and measure it for us, then we have all the info we need to build a tester that performs exactly like the purchased units.
Orifice size, anybody ??
All of the old Clymer motorcycle manuals illustrate doing a leakdown by pressurizing and recording pressure loss over a time period and then computing the percentages. The two-gauge testers mimick this same procedure but shortcut it by giving you a direct reading. Without an orifice, though, the leakdown numbers will be ridiculously low since the regulator can supply a large flow of air before showing a significant drop in pressure.
I'm not sure of the orifice size in these units, but if somebody will take one apart and measure it for us, then we have all the info we need to build a tester that performs exactly like the purchased units.
Orifice size, anybody ??
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