Did a compression test today

[Banchetta]

Just for a sanity check in this coversation.............................everyone knows that most piston aren't oval shaped right? They are design as a series of offset ovals. THe manufacturing process they go through to get that shape is called cam turning or eccentric turning.

 

Some oddball engines throughout history have actually used oval shaped pistons that were very noticeably shaped that way. I can think of a couple of Honda GP engines that did that. I think the design requirement that spawned that was a retardedly high rpm limit. I might be able to remember more after I eat lunch. :shoothead:

Yea, I think he took my wording differently, what I meant was make sure the cylinders were NOT egg-shaped from wear and tear. No use of putting new rings if the cylinder is worn out of round...which will then have to be bored round again.

[1.6i]

i know what you guys meant, a piston is oval.. not perfectly round when cold, not to the naked eye though, it expands into a full round shape when warmed up to operating temp....this is why is not good to rev a cold engine...

[Snopczynski]

Yep...

 

125 psi at sea level is stock, depending on elevation and motor integrity it will drop from there. SO, if your low elevation, it may be time for a hone and re-ring.

[1.6i]

when doing a compression test, do you guys kick fast, slow or about medium speed? does it matter? lol im not use to working on my banshee ima honda car technician for a living..haha

[Snopczynski]

when doing a compression test, do you guys kick fast, slow or about medium speed? does it matter? lol im not use to working on my banshee ima honda car technician for a living..haha

 

Usually medium to fast.

[1.6i]

Usually medium to fast.

 

 

nice, thanks

[dajogejr]

Doesn't matter.

The gauge has a check valve....so, it'll only hold as much PSI as the motor can generate....and stay there.

[Ducman]

I noticed you said you removed both plugs to do the test. I've always checked with the plug still in on the opposite side. 105 psi is pretty low for stock at sea level, I'm supprised that both cylinders are so low and still that even. You should kick fast but it shouldn't matter that much because you should only be able to get the guage to go up to a certain point and it wont climb any further. I usually kick at least 10 times but it really only takes a few.

[1.6i]

I noticed you said you removed both plugs to do the test. I've always checked with the plug still in on the opposite side. 105 psi is pretty low for stock at sea level, I'm supprised that both cylinders are so low and still that even. You should kick fast but it shouldn't matter that much because you should only be able to get the guage to go up to a certain point and it wont climb any further. I usually kick at least 10 times but it really only takes a few.

 

 

you only pull one plug @ a time? in the clymers it says to pull both plugs, who else pulls only one plug in here? seems like ill probably get better results that way, maybe??

 

as far as the psi climbing, each kick will generate about 30 psi, but when it gets to the top it only goes up about 5-10 psi each kick...sometimes a few kicks wont generate any psi

 

I got my buddys snap-on gauge, ima try it out today after work, ima post some numbers tomorrow morning..

ima do a cold engine comparison then warm, then hot..see what i come up with.. :shrugs: we'll see

[Banchetta]

Each side is sealed off from one another, so removing only one plug will do nothing...take both plugs out, it'll be alot easier to kick over.

[1.6i]

Well I feel like a complete fool, (doesnt seem to intrigue me either lol) i did some compression tests earlier, turns out i wasnt kickin hard enough when i was getting 105psi previously :: ..

well tonight i got 130psi in each cylinder with the snap-on gauge,and roughly about 125 psi with my matco gauge, this was with both plugs out on a completly cold engine..i warmed up the engne, then i got roughly 119psi in both cylinders.. kinda weird that there was less with a warm engine..

 

I found that i got about 5psi higher with the snap-on fitting threaded into the cylinder

matco (left) snap-on (right)

the matco threads were about the same height as the spark plug threads, so im going with the matco gauge set is more accurate as far as precise combustion chamber volume when threaded in..

 

Moral of the story is, when doing a compression test make sure you kick hard as if your trying to start it...I dont know what the hell i was doing before or why i was kicking it soft like a bitch..lol

 

Each side is sealed off from one another, so removing only one plug will do nothing...take both plugs out, it'll be alot easier to kick over.

 

 

actually, i got roughly about 4-5psi more with a sparkplug in the adjacent cylinder i was testing tonight..i think this is how ima test the compression in the future, it seems more accurate for this engine when testing for precise compression numbers..

Edited February 7, 2007 by 1.6i

[Banchetta]

Well I feel like a complete fool, (doesnt seem to intrigue me either lol) i did some compression tests earlier, turns out i wasnt kickin hard enough when i was getting 105psi previously :: ..

well tonight i got 130psi in each cylinder with the snap-on gauge,and roughly about 125 psi with my matco gauge, this was with both plugs out on a completly cold engine..i warmed up the engne, then i got roughly 119psi in both cylinders.. kinda weird that there was less with a warm engine..

 

I found that i got about 5psi higher with the snap-on fitting threaded into the cylinder

matco (left) snap-on (right)

the matco threads were about the same height as the spark plug threads, so im going with the matco gauge set is more accurate as far as precise combustion chamber volume when threaded in..

 

Moral of the story is, when doing a compression test make sure you kick hard as if your trying to start it...I dont know what the hell i was doing before or why i was kicking it soft like a bitch..lol

actually, i got roughly about 4-5psi more with a sparkplug in the adjacent cylinder i was testing tonight..i think this is how ima test the compression in the future, it seems more accurate for this engine when testing for precise compression numbers..

That is impossible, each side is COMPLETELY sealed from one another...I'd recheck that theory and if you get the same result, then you might want to think about splitting the cases. You center seal may be leaking or the gasket maker between the case halfs isn't sealing properly..good to see your compression is up there though...125psi on both cylinders is pretty good on a motor that is a couple of years old. Good maintenance. :thumbsup:

[1.6i]

That is impossible, each side is COMPLETELY sealed from one another...I'd recheck that theory and if you get the same result, then you might want to think about splitting the cases. You center seal may be leaking or the gasket maker between the case halfs isn't sealing properly..good to see your compression is up there though...125psi on both cylinders is pretty good on a motor that is a couple of years old. Good maintenance. :thumbsup:

 

 

i hear what your saying, who knows as long as my compression is legit im happy, thanks for all the help guys.

[Banchetta]

Over 75 guys from the East Coast will be going to Glamis for 9 days Feb12-21. We'll be at pad 2 w/ a couple of tractor trailers...Come on over and visit. Its always great to meet new people.

[1.6i]

Over 75 guys from the East Coast will be going to Glamis for 9 days Feb12-21. We'll be at pad 2 w/ a couple of tractor trailers...Come on over and visit. Its always great to meet new people.

 

 

cool, thanks for the invite, if i do go we'll be parked out in the wash somewhere, im not positive im going though..