---------------------------------------------------------- RV-List Digest Archive --- Total Messages Posted Wed 06/25/14: 11 ---------------------------------------------------------- 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 _____________________________________ Time: 12:46:16 PM PST US Subject: RV-List: 70 psi compression From: Thomas Sargent 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 _____________________________________ Time: 12:59:42 PM PST US From: Linn Walters Subject: Re: RV-List: 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 _____________________________________ Time: 01:21:25 PM PST US From: "Carl Froehlich" 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 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 _____________________________________ Time: 01:41:02 PM PST US Subject: RE: RV-List: 70 psi compression From: Vincent Himsl Thanks for the document! VinceH RV8-flying --- Original Message --- From: "Carl Froehlich" 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 _____________________________________ Time: 03:09:35 PM PST US From: Kelly McMullen Subject: Re: RV-List: 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 _____________________________________ Time: 04:11:22 PM PST US Subject: Re: RV-List: 70 psi compression From: Thomas Sargent 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 _____________________________________ Time: 04:25:25 PM PST US From: "William Greenley" 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] 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 _____________________________________ Time: 04:42:41 PM PST US From: Carl Froehlich Subject: Re: RV-List: 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 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 3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3 D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D 3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3 D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D 3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3 D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D 3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3 D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > ________________________________ Message 9 _____________________________________ Time: 06:45:25 PM PST US Subject: Re: RV-List: 70 psi compression From: vanremog@aol.com 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 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 ____________________________________ Time: 08:06:01 PM PST US From: Kelly McMullen Subject: Re: RV-List: 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 ____________________________________ Time: 08:12:29 PM PST US From: Linn Walters Subject: Re: RV-List: 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 > To: rv-list > 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 > ] *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 > > * > * > > > * ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message rv-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/RV-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/rv-list Browse Digests http://www.matronics.com/digest/rv-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.