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Compression testing

Redfin

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In some other thread we have been chatting about the length of hose connected before the gauge. Here is what I found.

I used my Mityvac comp tester with two different lengths of hose one being roughly 6" and the other 12".image.jpeg

The saw is my 446 which has been 205 psi since forever. The saw was drained of fuel and idled dry for comparison. I used the short 6" length and pulled probably 10 times to make sure it was at max comp. I then released and counted the pulls to get to max. It took 6 pulls to get to 205 psi.image.jpeg

I then attached the 12" hose and pulled 6 times I ended up at 175 psi.image.jpeg
I released the pressure and pulled until the gauge stopped which was 205 psi and it took 12 pulls. This verified in my noodle if the schrader is at the tip in the combustion chamber and its functioning correctly the length of hose once filled does not add to chamber volume.image.jpeg
 

czar800

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Great thread, thanks for testing the differents.
 

Warped5

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One thin I'd like to add ...

I had an Actron gauge from AZ that I always thought was made well etc .... but always doubted its accuracy ...

I got another gauge in a lot of tools I bought and found it gave readings 10 -15 PSI higher ...

Then discovered that the Actron gauge had a quick-connect just below the head that was leaking ...

Needless to say, the Actron gauge is now in the scrap bucket.
 

czar800

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One thin I'd like to add ...

I had an Actron gauge from AZ that I always thought was made well etc .... but always doubted its accuracy ...

I got another gauge in a lot of tools I bought and found it gave readings 10 -15 PSI higher ...

Then discovered that the Actron gauge had a quick-connect just below the head that was leaking ...

Needless to say, the Actron gauge is now in the scrap bucket.

I have the same problem with my AZ gauge it's going back I just bought it. Brand new junk!
 

jmssaws

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I had 2 conflicting guage's so I threw one away and use the other.

I rarely check a saw anymore.
 

jmssaws

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What's the highest compression saw anybody has personally checked?
 

czar800

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I pulled 225 on my 026 with a junk gauge.
 

Stihlbro

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I love this thread. These compression reading are just a reference. It is only a static reading. Too much variance with hot or cold. How much oil you run. What altitude your at. But one thing for sure is the Internet likes some compression.

@Redfin thanks for taking the time on your end. The results are not deniable.
 
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