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Compression

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Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Tue Jul 07, 2009 8:24 am Post subject: Compression

Did you try removing the rocker covers and giving each rocker a few  

love taps right over the valve? This will often settle a valve onto  

its seat and give a few or several more pounds of compression. Going  

by the recently published "Summary of significant engine changes",  

you have a hydraulic lifter engine, right? If so, it sounds like the  

"high leak lifter" engine. I don't know how this would affect the  

tapping-on-the-valve procedure, so you might want to ask Pete if  

that's ok to do.



Lynn Matteson

Kitfox IV Speedster, taildragger

Jabiru 2200, #2062, 695.8 hrs

Sensenich 62"x46" Wood prop

Electroair direct-fire ignition system

Status: flying

do not archive



On Jul 7, 2009, at 11:30 AM, BobbyPaulk(at)COMCAST.NET wrote:



 	  Quote: 	
		   all,



 i have just taken differential compression test on my 3300A with 84  

 hrs S.N. 1141.( Conditional Inspection )  No. 2 and 6 had 75 & 77  

 the rest had low to mid 60's. i could rock the prop to seat the  

 rings and get another 5 ~ 6 lbs. while on #5 near the oil collector  

 bottle i could feel air out the bottle vent so the air is going  

 thru the rings and pressurizing the crankcase. Test was on a cold  

 engine setting up for about 2 weeks.

 my question is at 84 hrs could this many cylinders have rings not  

 yet seated. last year all were in the high 70's. the engine starts  

 fine as always and i have not noticed any power drop. the first 40  

 hrs or so the engine ran too lean and it was difficult to control  

 high EGT / CHT's.



 any ideas??



 Bobby

 601 XL

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_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

tonyplane(at)bellsouth.ne
Guest

Posted: Tue Jul 07, 2009 11:54 am Post subject: Compression

Bobby,

  

 Have you tried "dynamic"compression testing (see  compression testing Page 18 of Jab Instruction & Maintenance Manual, Rev 3  dated 18 Jul 2008. (this is for the solid lifter 3300A - suspect the  hydraulic lifter is the same) 

 Para 5.7.8  "Compression Testing:   Condition of compression can be done by a compression gauge.  Wide open  throttle, engine warm.  Turn over on starter.  Below 90 psi would  indicate removal of head and possibly cylinder>

  

 At my last annual, almost a year ago, I read 160#,  160#, 160#, 165#, 165 and 170# on my Jab with 408 hrs.  Not much,  if any, change from the years before.

  

 Tony Graziano

 ZodiacXL/Jab3300A - Ser 33A644; N493TG; 509  hrs.

  

  

 [quote]   ---

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mjmorea(at)videotron.ca
Guest

Posted: Tue Jul 07, 2009 12:25 pm Post subject: Compression

I have a similar problem. Just worse..

  

 After 140 hours my engine is leaking through the  valves and the rings.

 The differentail test gives : 40/80, 49/80, 34/80,  55/80

 Strangely a compression test gives: 153, 156, 147,  159

  

 At 90 hours I had the cylinders were honed and the  rings changed!!

  

 I don't know were to turn to obtain a rational  explanation..

  

  

 Michel, Q-2 (Ser# 22A1093)



 [quote]   ---

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Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Thu Jul 09, 2009 8:12 am Post subject: Compression

I’ve tried dynamic tests over the years and found them to be more lying than a politician on the campaign trail.  Also when they do actually find a low cylinder you still have the problem of finding where compression is lost.  

   

Noel  

       

From: owner-jabiruengine-list-server(at)matronics.com [mailto:owner-jabiruengine-list-server(at)matronics.com] On Behalf Of T. Graziano

 Sent: 07 July 2009 17:23

 To: jabiruengine-list(at)matronics.com

 Subject: Re: Compression  

  

  

     

Bobby,  

    

   

    

Have you tried "dynamic"compression testing (see compression testing Page 18 of Jab Instruction & Maintenance Manual, Rev 3 dated 18 Jul 2008. (this is for the solid lifter 3300A - suspect the hydraulic lifter is the same)   

    

Para 5.7.8  "Compression Testing:  Condition of compression can be done by a compression gauge.  Wide open throttle, engine warm.  Turn over on starter.  Below 90 psi would indicate removal of head and possibly cylinder>  

    

   

    

At my last annual, almost a year ago, I read 160#, 160#, 160#, 165#, 165 and 170# on my Jab with 408 hrs.  Not much, if any, change from the years before.  

    

   

    

Tony Graziano  

    

ZodiacXL/Jab3300A - Ser 33A644; N493TG; 509 hrs.  

    

   

    

   

   	  Quote: 	
		      

----- Original Message -----   

    

From: BobbyPaulk(at)COMCAST.NET (BobbyPaulk(at)COMCAST.NET)   

    

To: jabiruengine-list-digest(at)matronics.com (jabiruengine-list-digest(at)matronics.com)   

    

Sent: Tuesday, July 07, 2009 10:30 AM  

    

Subject: JabiruEngine-List: Compression  

    

   

    

all,

 

 i have just taken differential compression test on my 3300A with 84 hrs S.N. 1141.( Conditional Inspection )  No. 2 and 6 had 75 & 77 the rest had low to mid 60's. i could rock the prop to seat the rings and get another 5 ~ 6 lbs. while on #5 near the oil collector bottle i could feel air out the bottle vent so the air is going thru the rings and pressurizing the crankcase. Test was on a cold engine setting up for about 2 weeks.

 my question is at 84 hrs could this many cylinders have rings not yet seated. last year all were in the high 70's. the engine starts fine as always and i have not noticed any power drop. the first 40 hrs or so the engine ran too lean and it was difficult to control high EGT / CHT's.

 

 any ideas??

 

 Bobby

 601 XL   

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Kitfox III-A
Aerocet 1100 Floats

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Thu Jul 09, 2009 3:51 pm Post subject: Re: Compression

Hi Guys,



Are you making sure to test with an engine up at operating temps. Shouldn't be cold.

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mjmorea(at)videotron.ca
Guest

Posted: Sat Jul 11, 2009 4:04 pm Post subject: Compression

Not quite at operating temp but hot....



Michel



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