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compression

 
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Lukasczyk(at)gmx.net
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PostPosted: Sun Jul 15, 2007 7:39 am    Post subject: compression Reply with quote
Hello

Yesterday, I checked my compression and found all cylinders to be 80/77 exept the famous fourth one. My number 4 was at 80/72. The oil consumption is quite normal at a little over one quart every 20 hours and I have not noticed any performance losses or increased oil consumption over the last 100 hours. My number 4 is not runnig hot, nor are exhaust temperatures above normal. Head-temp is usually around 350F and oil temperatures vary between 190F and 210F depending on the power setting. The plugs looked good and an older test-report (done 100 hours ago) indicated all cylinders to be 80/76 exept number 3 (three) which was at 80/74 at that time. I am confused here and it looks like things got mixed up. Do I have to worry about the result I got? The engine was not at it's normal operation temperature when I performed the test and I know it is supposed to be. There was another strange effect, though. The compression-test is done when the piston is at or near TDC. There the prop w
ill not move although the cylinder is pressurized. I read 80/72 (#4) and a little less once I moved the prop slightly (only 1/4 inch). Does that necessarily indicate a ring problem?

Thanks you for your opinion

Thomas, RV-4
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pitts_pilot(at)bellsouth.
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PostPosted: Sun Jul 15, 2007 8:18 am    Post subject: compression Reply with quote
Thomas Lukasczyk wrote:

Quote:


Hello

Yesterday, I checked my compression and found all cylinders to be 80/77 exept the famous fourth one. My number 4 was at 80/72. The oil consumption is quite normal at a little over one quart every 20 hours and I have not noticed any performance losses or increased oil consumption over the last 100 hours. My number 4 is not runnig hot, nor are exhaust temperatures above normal. Head-temp is usually around 350F and oil temperatures vary between 190F and 210F depending on the power setting. The plugs looked good and an older test-report (done 100 hours ago) indicated all cylinders to be 80/76 exept number 3 (three) which was at 80/74 at that time. I am confused here and it looks like things got mixed up. Do I have to worry about the result I got?

I wouldn't. The numbers will change a little no matter what you do ....

a little carbon under the seat or maybe the ring gaps are closer
together ..... who knows???

Quote:
The engine was not at it's normal operation temperature when I performed the test and I know it is supposed to be.

Well, it should be. Makes it hard on the fingers getting the plugs out,

but with everything up to temp you'll see better results on the test.
Getting some oil under the rings also helps.

Quote:
There was another strange effect, though. The compression-test is done when the piston is at or near TDC. There the prop w
ill not move although the cylinder is pressurized. I read 80/72 (#4) and a little less once I moved the prop slightly (only 1/4 inch). Does that necessarily indicate a ring problem?

Not really. I could have said "no", but I'm no expert. The rings will

flex a little and the seal isn't as good. The very top of the cylinder
doesn't wear as much over time as the rest of the barrel. Your numbers
are fairly good, so I wouldn't worry.
Linn ..... just my opinion

Quote:


Thanks you for your opinion

Oh, you're quite welcome .... I have a lot!!!

do not archive

Quote:

Thomas, RV-4




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rocketbob(at)gmail.com
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PostPosted: Sun Jul 15, 2007 10:13 am    Post subject: compression Reply with quote
Go fly it a couple of times then check it again, hot. Chances are the compression numbers will fall in line with your other cylinders. If the ring gaps line up then you will get a low compression reading.

Regards,
Bob Japundza
RV-6 flying F1 under const.

On 7/15/07, Thomas Lukasczyk <Lukasczyk(at)gmx.net (Lukasczyk(at)gmx.net)> wrote: [quote]--> RV-List message posted by: "Thomas Lukasczyk" < Lukasczyk(at)gmx.net (Lukasczyk(at)gmx.net)>

Hello

Yesterday, I checked my compression and found all cylinders to be 80/77 exept the famous fourth one. My number 4 was at 80/72. The oil consumption is quite normal at a little over one quart every 20 hours and I have not noticed any performance losses or increased oil consumption over the last 100 hours. My number 4 is not runnig hot, nor are exhaust temperatures above normal. Head-temp is usually around 350F and oil temperatures vary between 190F and 210F depending on the power setting. The plugs looked good and an older test-report (done 100 hours ago) indicated all cylinders to be 80/76 exept number 3 (three) which was at 80/74 at that time. I am confused here and it looks like things got mixed up. Do I have to worry about the result I got? The engine was not at it's normal operation temperature when I performed the test and I know it is supposed to be. There was another strange effect, though. The compression-test is done when the piston is at or near TDC. There the prop w
ill not move although the cylinder is pressurized. I read 80/72 (#4) and a little less once I moved the prop slightly (only 1/4 inch). Does that necessarily indicate a ring problem?

Thanks you for your opinion

Thomas, RV-4
--
Psssst! Schon vom neuen GMX MultiMessenger gehört?
Der kanns mit allen: http://www.matronics.com/=================== =========

[b]

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