Today's Message Index:
----------------------
1. 12:46 PM - 70 psi compression (Thomas Sargent)
2. 12:59 PM - Re: 70 psi compression (Linn Walters)
3. 01:21 PM - Re: 70 psi compression (Carl Froehlich)
4. 01:41 PM - Re: 70 psi compression (Vincent Himsl)
5. 03:09 PM - Re: 70 psi compression (Kelly McMullen)
6. 04:11 PM - Re: 70 psi compression (Thomas Sargent)
7. 04:25 PM - Re: 70 psi compression (William Greenley)
8. 04:42 PM - Re: 70 psi compression (Carl Froehlich)
9. 06:45 PM - Re: 70 psi compression (vanremog@aol.com)
10. 08:06 PM - Re: 70 psi compression (Kelly McMullen)
11. 08:12 PM - Re: 70 psi compression (Linn Walters)
Message 1
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Subject: | 70 psi compression |
In the last compression test of my IO-360, after running the engine only a
minute or two, showed 70 psi on cyl #4. The A&P doing the measurement
removed the dip stick and listened at the oil filler pipe. He could hear
hissing which he says means it's leaking past the rings, which didn't seem
to bother him much. Only 130 SMOH. Not using any oil.
Is it worth repeating the measurement after flying the thing a few hours?
I've been told the gaps in the rings can line up and affect the measurement.
Should I have run the engine longer than a couple minutes before doing the
measurement?
How low is "low"? At what point do I have to rebuild/replace the cylinder?
Thanks for any info/opinions/war stories.
--
Tom Sargent
Message 2
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Subject: | Re: 70 psi compression |
I'm no engine guru but my experience is free .....
On 6/25/2014 3:45 PM, Thomas Sargent wrote:
> In the last compression test of my IO-360, after running the engine
> only a minute or two, showed 70 psi on cyl #4. The A&P doing the
> measurement removed the dip stick and listened at the oil filler pipe.
> He could hear hissing which he says means it's leaking past the rings,
> which didn't seem to bother him much. Only 130 SMOH. Not using any oil.
>
> Is it worth repeating the measurement after flying the thing a few
> hours? I've been told the gaps in the rings can line up and affect
> the measurement.
I'd run it again ...... a short flight around the patch should do it
..... and the gaps aligning is possible, but IMHO not probable.
>
> Should I have run the engine longer than a couple minutes before doing
> the measurement?
I would, just to get the cylinder temps up a bit.
>
> How low is "low"? At what point do I have to rebuild/replace the
> cylinder?
That's up to your A&P/IA .... but I believe 60 is a worry point.
>
> Thanks for any info/opinions/war stories.
> --
> Tom Sargent
> *
>
>
> *
Message 3
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Subject: | 70 psi compression |
I would throw this measurement away.
Go fly the airplane and get all engine up to normal temperatures then
redo the compression test. Do not be surprised if a cylinder changes ~2
psi or so from test to test. Log the results in the engine log book
after each test. I typically do a compression test at each oil change,
but not less than at each annual. If you don=99t have a
compression tester then perhaps you should. This is something I view as
a standard maintenance tool =93 and are available at ACS for less
than $100.
Attached is the Lycoming SI on this.
Carl
From: owner-rv-list-server@matronics.com
[mailto:owner-rv-list-server@matronics.com] On Behalf Of Thomas Sargent
Sent: Wednesday, June 25, 2014 3:45 PM
Subject: RV-List: 70 psi compression
In the last compression test of my IO-360, after running the engine only
a minute or two, showed 70 psi on cyl #4. The A&P doing the measurement
removed the dip stick and listened at the oil filler pipe. He could hear
hissing which he says means it's leaking past the rings, which didn't
seem to bother him much. Only 130 SMOH. Not using any oil.
Is it worth repeating the measurement after flying the thing a few
hours? I've been told the gaps in the rings can line up and affect the
measurement.
Should I have run the engine longer than a couple minutes before doing
the measurement?
How low is "low"? At what point do I have to rebuild/replace the
cylinder?
Thanks for any info/opinions/war stories.
--
Tom Sargent
Message 4
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Subject: | 70 psi compression |
Thanks for the document!
VinceH
RV8-flying
--- Original Message ---
From: "Carl Froehlich" <carl.froehlich@verizon.net>
Sent: June 25=2C 2014 1:28 PM
Subject: RE: RV-List: 70 psi compression
I would throw this measurement away.
Go fly the airplane and get all engine up to normal temperatures then redo
the compression test. Do not be surprised if a cylinder changes ~2 psi or
so from test to test. Log the results in the engine log book after each te
st. I typically do a compression test at each oil change=2C but not less t
han at each annual. If you don=99t have a compression tester then pe
rhaps you should. This is something I view as a standard maintenance tool
=93 and are available at ACS for less than $100.
Attached is the Lycoming SI on this.
Carl
From: owner-rv-list-server@matronics.com [mailto:owner-rv-list-server@matro
nics.com] On Behalf Of Thomas Sargent
Sent: Wednesday=2C June 25=2C 2014 3:45 PM
Subject: RV-List: 70 psi compression
In the last compression test of my IO-360=2C after running the engine only
a minute or two=2C showed 70 psi on cyl #4. The A&P doing the measurement
removed the dip stick and listened at the oil filler pipe. He could hear hi
ssing which he says means it's leaking past the rings=2C which didn't seem
to bother him much. Only 130 SMOH. Not using any oil.
Is it worth repeating the measurement after flying the thing a few hours?
I've been told the gaps in the rings can line up and affect the measurement
.
Should I have run the engine longer than a couple minutes before doing the
measurement?
How low is "low"? At what point do I have to rebuild/replace the cylinder
?
Thanks for any info/opinions/war stories.
--
Tom Sargent
Message 5
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Subject: | Re: 70 psi compression |
I assume we are talking an experimental here, so no IA involvement
needed, just A&P for condition inspection if you are not the builder.
If the only leakage is past the rings, oil consumption will guide you to
when you feel the need to do something about the cylinder.
I would fly the engine hard for at least 10 hours, to see if the rings
did not fully seat on that cylinder. Running it at 75% or even a bit
higher, as long as you keep cylinder temps below 400 will not hurt
anything, and may get those rings seated. 70/80 is nothing to worry
about. Maybe a bit low for as low a time engine as you havel
As long as the leakage is not from a valve you can go down below 50/80
and still make full rated power.
Kelly
A&P/IA
EAA Tech Counselor
On 6/25/2014 12:58 PM, Linn Walters wrote:
> I'm no engine guru but my experience is free .....
> How low is "low"? At what point do I have to rebuild/replace the
> cylinder?
> That's up to your A&P/IA .... but I believe 60 is a worry point.*\\*
Message 6
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Subject: | Re: 70 psi compression |
Thanks for all the good information.
Reading the Lycoming Service instructions, I should note that cyl#1 showed
88psi. I was doing the test as part of the annual inspection. Last year
they were all in the 72 - 78 range I think. What does an anomalously high
reading indicate? Off hand I would have guessed that the higher the
better, but apparently not. Lyc. says more than 15psi difference is trouble.
I think I need to repeat this whole test soon after actually flying the
plane.
I'm still finishing the annual, I haven't flown it for a couple weeks.
>
>
--
Tom Sargent
Message 7
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Subject: | 70 psi compression |
An 88 means something is wrong with the equipment or the methodology.
The max is 80 with the standardized orifice.
From: owner-rv-list-server@matronics.com
[mailto:owner-rv-list-server@matronics.com] On Behalf Of Thomas Sargent
Sent: Wednesday, June 25, 2014 7:11 PM
Subject: Re: RV-List: 70 psi compression
Thanks for all the good information.
Reading the Lycoming Service instructions, I should note that cyl#1
showed 88psi. I was doing the test as part of the annual inspection.
Last year they were all in the 72 - 78 range I think. What does an
anomalously high reading indicate? Off hand I would have guessed that
the higher the better, but apparently not. Lyc. says more than 15psi
difference is trouble.
I think I need to repeat this whole test soon after actually flying the
plane.
I'm still finishing the annual, I haven't flown it for a couple weeks.
--
Tom Sargent
Message 8
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Subject: | Re: 70 psi compression |
Since the test rig provides regulated 80 psi input (if properly adjusted), y
our 88/80 reading makes no sense. In other words zero leakage means you wou
ld read 80/80. I suspect the test was done wrong.
Carl
> On Jun 25, 2014, at 7:10 PM, Thomas Sargent <sarg314@gmail.com> wrote:
>
>
> Thanks for all the good information.
>
> Reading the Lycoming Service instructions, I should note that cyl#1 showed
88psi. I was doing the test as part of the annual inspection. Last year th
ey were all in the 72 - 78 range I think. What does an anomalously high rea
ding indicate? Off hand I would have guessed that the higher the better, bu
t apparently not. Lyc. says more than 15psi difference is trouble.
>
> I think I need to repeat this whole test soon after actually flying the pl
ane.
>
> I'm still finishing the annual, I haven't flown it for a couple weeks.
>
>
>
> --
> Tom Sargent
> is
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>
>
Message 9
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Subject: | Re: 70 psi compression |
Just a wild question since no one has asked it...How can one get an 88 psig
aircraft bleed down type compression reading with 80 psig supplied air?
-----Original Message-----
From: William Greenley <wgreenley@gmail.com>
Sent: Wed, Jun 25, 2014 4:26 pm
Subject: RE: RV-List: 70 psi compression
An 88 means something is wrong with the equipment or the methodology. The m
ax is 80 with the standardized orifice.
From: owner-rv-list-server@matronics.com [mailto:owner-rv-list-server@matro
nics.com] On Behalf Of Thomas Sargent
Sent: Wednesday, June 25, 2014 7:11 PM
Subject: Re: RV-List: 70 psi compression
Thanks for all the good information.
Reading the Lycoming Service instructions, I should note that cyl#1 showed
88psi. I was doing the test as part of the annual inspection. Last year th
ey were all in the 72 - 78 range I think. What does an anomalously high re
ading indicate? Off hand I would have guessed that the higher the better,
but apparently not. Lyc. says more than 15psi difference is trouble.
I think I need to repeat this whole test soon after actually flying the pla
ne.
I'm still finishing the annual, I haven't flown it for a couple weeks.
--
Tom Sargent
http://www.matronics.com/Navigator?RV-List
http://forums.matronics.com
http://www.matronics.com/contribution
Message 10
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Subject: | Re: 70 psi compression |
One needs to check the calibration of the compression tester. Easy way
is to not connect the hose to the cylinder, then crank the primary gauge
up to 80. The secondary should read 80 also. If more than a pound or so
in either direction it needs to be recalibrated.
88 over 80 is not physically possible. 80/80 is the absolute best you
can get.
On 6/25/2014 4:10 PM, Thomas Sargent wrote:
>
> Thanks for all the good information.
>
> Reading the Lycoming Service instructions, I should note that cyl#1
> showed 88psi. I was doing the test as part of the annual inspection.
> Last year they were all in the 72 - 78 range I think. What does an
> anomalously high reading indicate? Off hand I would have guessed that
> the higher the better, but apparently not. Lyc. says more than 15psi
> difference is trouble.
>
> I think I need to repeat this whole test soon after actually flying
> the plane.
>
> I'm still finishing the annual, I haven't flown it for a couple weeks.
>
>
> --
> Tom Sargent
> *
>
>
> *
Message 11
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Subject: | Re: 70 psi compression |
On 6/25/2014 9:44 PM, vanremog@aol.com wrote:
> Just a wild question since no one has asked it...How can one get an 88
> psig aircraft bleed down type compression reading with 80 psig
> supplied air?
You can't if you use the differential gauge properly. I can only
surmise that 88 was a typo.
Linn
> -----Original Message-----
> From: William Greenley <wgreenley@gmail.com>
> To: rv-list <rv-list@matronics.com>
> Sent: Wed, Jun 25, 2014 4:26 pm
> Subject: RE: RV-List: 70 psi compression
>
> An 88 means something is wrong with the equipment or the methodology.
> The max is 80 with the standardized orifice.
> *From:*owner-rv-list-server@matronics.com
> <mailto:owner-rv-list-server@matronics.com>
> [mailto:owner-rv-list-server@matronics.com
> <mailto:owner-rv-list-server@matronics.com?>] *On Behalf Of *Thomas
> Sargent
> *Sent:* Wednesday, June 25, 2014 7:11 PM
> *To:* rv-list
> *Subject:* Re: RV-List: 70 psi compression
> Thanks for all the good information.
>
> Reading the Lycoming Service instructions, I should note that cyl#1
> showed 88psi. I was doing the test as part of the annual inspection.
> Last year they were all in the 72 - 78 range I think. What does an
> anomalously high reading indicate? Off hand I would have guessed that
> the higher the better, but apparently not. Lyc. says more than 15psi
> difference is trouble.
>
> I think I need to repeat this whole test soon after actually flying
> the plane.
>
> I'm still finishing the annual, I haven't flown it for a couple weeks.
>
>
> --
> Tom Sargent
> * *
> * *
> **
> **
> **
> **
> **
> *http://www.matronics.com/Navigator?RV-List*
> **
> **
> *http://forums.matronics.com*
> **
> **
> **
> **
> *http://www.matronics.com/contribution*
> **
> * *
> *
>
> t="_blank">http://www.matronics.com/Navigator?RV-List
> tp://forums.matronics.com
> _blank">http://www.matronics.com/contribution
>
> *
> *
>
>
> *
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