Compression testing

[Redfin]

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".

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.

I then attached the 12" hose and pulled 6 times I ended up at 175 psi.
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.

 

[Deets066]

Nice post, thanks for clearing that up.

 

[czar800]

Great thread, thanks for testing the differents.

 

[Warped5]

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]

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]

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

I rarely check a saw anymore.

 

[tree monkey]

I have 4 and don't believe any of them

 

[jmssaws]

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

 

[tree monkey]

1 gauge has a pin at 350. so higher then that

 

[Deets066]

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

I know Tmonk has built one that went caploowey from to much comp

 

[panteliss]

I have 4 and don't believe any of them

+1

 

[jmssaws]

1 gauge has a pin at 350. so higher then that

Small cc?
I got a 90cc that will go 240 or better and it's hard to check.

 

[Deets066]

Small cc?
I got a 90cc that will go 240 or better and it's hard to check.

He probly had to pull the starter off his pick up

 

[tree monkey]

440 head saw

 

[czar800]

I have 4 and don't believe any of them

It really seem like they all throw different numbers... I've used 3 gauges back to back and got a wide range of readings. So what's a man to do... Put the saw in some wood a truly find out how she runs!!

 

[tree monkey]

I know Tmonk has built one that went caploowey from to much comp

I don't think 180 caused that

 

[drf256]

Thanks for the experiment. Myth busted.

 

[Deets066]

I don't think 180 caused that

I thought that saw with over 300 took a chit?

 

[czar800]

I pulled 225 on my 026 with a junk gauge.

 

[Stihlbro]

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.