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avidflyer01
Joined: 07 Jun 2007
Posts: 9
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 Posted: Fri Jun 08, 2007 2:28 pm Post subject: compression values |
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hi folks,
I would like to find out what are typical compression values on a
recent 2200; could those who measured their compressions give me their
results, together with approx engine hours and age?
as I have a problem with a leaky valve in one cylinder I carried out
some serious tests on my engine and found that on the three "good"
cylinders I have only 122psi (8.6 bar). I've heard about one engine
that at 300hrs had as much as 160psi (11.2bar), yet I also heard that
my 122psi is a reasonable compression.
My compressions were taken with a warm engine, one sparkplug per
cylinder removed, throttle fully open, good battery. Engine has 100
hrs, 2 years old (hyd lifters).
I also did a leak down test: pressure drop on good cylinders were 9%,
11% and 14%; it was 35% on the bad one.
thanksfor your help
Martin
Avid Flyer / Jab powered
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ptag.dev(at)tiscali.co.uk
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| Posted: Sat Jun 09, 2007 2:47 pm Post subject: compression values |
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Hi! Martin
25% down on the leak down test is maximum permissible on any cylinder..
Otherwise IMHO the Compression test is barely worth the bother.
Regards
Bob H
Robt.C.Harrison
--
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Float Flyr
Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland
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| Posted: Sun Jun 10, 2007 4:23 am Post subject: Compression values |
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Martin:
The standard automotive compression tester is about as useful as chewing gum
in the gas line. They lie! Actually they lie like troopers after a bad
day!
The only compression test worth looking at is a differential compression
test. This is done by flowing 80 psi of air into a cylinder at TDC and
checking how much pressure is lost in that cylinder. A perfect score would
be 80 and lesser scores would be in the seventies you will have problems in
the mid sixties. ( sounds familiar doesn't it  )
The differential test is as close as you can come to testing the cylinder in
operation. It has the added abilities to accurately find where the problems
are... If you head air leaking form the engine base then you have bad rings
on that cylinder, If it comes from the intake manifold it's the intake valve
and of course if you hear hissing at the exhaust the exhaust valve will need
work.
To do the differential test you will have to remove plug from each cylinder
just as you have to do with the automotive tester. While you are doing this
it's a good time to have a nice close look at your spark plugs. Cylinders
suffering lower compression may also display a bit darker plug as the fuel
doesn't burn completely in the cylinder.
Getting a differential test done on each annual would be a good idea just
the same as cutting open oil filters and looking for large metal flakes.
Hope this helps.
Noel Loveys, RPP, AME intern
Campbellton, Newfoundland,
Canada
Kitfox Mod III-A, 582, B box, Ivo IFA
Aerocet 1100s
noelloveys(at)yahoo.ca
| Quote: | Time: 03:28:48 PM PST US
Subject: compression values
From: "avidflyer01" <vegayacht(at)club.fr>
hi folks,
I would like to find out what are typical compression values on a
recent 2200; could those who measured their compressions give me their
results, together with approx engine hours and age?
as I have a problem with a leaky valve in one cylinder I carried out
some serious tests on my engine and found that on the three "good"
cylinders I have only 122psi (8.6 bar). I've heard about one engine
that at 300hrs had as much as 160psi (11.2bar), yet I also heard that
my 122psi is a reasonable compression.
My compressions were taken with a warm engine, one sparkplug per
cylinder removed, throttle fully open, good battery. Engine has 100
hrs, 2 years old (hyd lifters).
I also did a leak down test: pressure drop on good cylinders were 9%,
11% and 14%; it was 35% on the bad one.
thanksfor your help
Martin
Avid Flyer / Jab powered
|
| | - The Matronics JabiruEngine-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?JabiruEngine-List |
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_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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