850 Compression numbers

[Powerstroked162]

Who has the stock compressions number and stock compression ratio? I've searched high and low, been told something different from 3 different aftermarket shops as well lol

 

[kanedog]

What are your compression numbers?

 

[Snopro_69]

If talking psi per cylinder, not compression ratio. I'm at 125 psi on each at 2100FT on my 2020. Brand spanking, barely has idled yet even.

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[Indy_500]

And remember. Gauges vary!!! Both the Polaris 800s I’ve owned haven’t been over 115 psi, which is right where all the 600s I’ve owned have been with this gauge also. I wouldn’t be so concerned about the number as I would be that they are the same. Compression doesn’t tell the entire story though. Piston in the pic still had 115 psi (same as other side) on my 16 800ho and ran ok. Last year I also seized up an 04 pro x 600 (my trail burner for at home) I let it cool down broke it free and ran it 50 miles back to the truck. Nikasil was torn off in multiple spots of the cylinder and piston was mangled. Still had 115 psi.

 

[Powerstroked162]

I need the info for reference points is all. Working on something fun

 

[Rubickon]

how do I get my compression numbers?

 

[Snopro_69]

Put compression tester in. Unplug other spark plug. Hold wide open and pull hard 5 times. That's how I do it.

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[Big10inch]

As discussed a hundred times on this forum, compression testing is mostly worthless on a sled. You need to do leak down testing to find out how well it is sealing. Bad pistons and good numbers tell the truth, toss the compression tester, upgrade to a leak down tester. Much better way to monitor the health of your engine.

 

[kanedog]

We are trying to establish a Polaris 850 compression baseline for comparison of sled to sled bigdum10inch. Come on now, pay attention. Chop chop

 

[madmax]

Also not a bad idea to get a baseline compression on your personal sled and follow there compression numbers throughout the year.

 

[Rubickon]

thanks guys!

 

[Powerstroked162]

As discussed a hundred times on this forum, compression testing is mostly worthless on a sled. You need to do leak down testing to find out how well it is sealing. Bad pistons and good numbers tell the truth, toss the compression tester, upgrade to a leak down tester. Much better way to monitor the health of your engine.

Literally not relevant to my post.

 

[Powerstroked162]

Found a local sled. Pulled 127lbs average at 700’ elevation. Thanks for the help fellas

 

[Big10inch]

Literally not relevant to my post.

Well since other peoples compression numbers aren't relevant either... does it matter?

If you need the static compression number, email Polaris, if you are serious about needing it for mods...

 

[Big10inch]

We are trying to establish a Polaris 850 compression baseline for comparison of sled to sled bigdum10inch. Come on now, pay attention. Chop chop

Yes and you have been here long enough to know that 1) you can not compare numbers from one tester to another, 2) from one elevation to another 3) one test procedure from another. Then to top it off somebody proves my point by showing a ruined piston that still showed good compression. How thick can you get?

 

[kanedog]

Bigthick10inch?

 

[Powerstroked162]

Well since other peoples compression numbers aren't relevant either... does it matter?

If you need the static compression number, email Polaris, if you are serious about needing it for mods...

Lol

 

[Big10inch]

I guess it makes sense here in Polaris land. If you monitor compression, no matter how bad it runs, you can say it has good compression... LOL Polaris lives off of you guys, laughing all the way to the bank.

 

[Powerstroked162]

You missed the point and continue to miss the point. It’s just the Internet, don’t take it like a big10inch ??

 

[Teth-Air]

Yes and you have been here long enough to know that 1) you can not compare numbers from one tester to another, 2) from one elevation to another 3) one test procedure from another. Then to top it off somebody proves my point by showing a ruined piston that still showed good compression. How thick can you get?

Correct me if I am wrong but I believe elevation and barometric pressure should have nothing to do with the compression results on the gauge. You are measuring gauge pressure and not absolute pressure here. If there is less air pressure pushing into the cylinder at higher elevation, there is also less external pressure exerted on the Bourdon tube of the compression tester. They cancel each other out and it is a simple multiplier of volumes of air.