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  #1  
Old 10-21-2017, 09:15 PM
Chris Engler Chris Engler is offline
 
Join Date: Aug 2012
Location: Greene, NY
Posts: 86
Default Mystery of the Coughing XP-400 Finally Solved!

http://tinypic.com/usermedia.php?uo=...c#.Wev41GhSyM8

For those of you that have been following my "XP-400 Still Coughing" thread, I'm delighted to report I had to start a new thread with a different name since the problem has been identified.

After spending 2 months and changing out fuel servos, mags, exhaust, checking plugs, spider, injectors, confirming fuel flow and pressure, etc. etc., and not finding anything, I spent today at the airport, pulled the engine off the airplane, removed the accessory case and there it was....the cam to crank gear train was "one tooth off".

The engine would start and run fine till 2500 RPM then stumble and sputter rich. Leaning would clean up the coughing and allow 2600 RPM static. Many (including the mechanic on our filed) felt the engine would run rough throughout the entire RPM range with the cam timing off but Birddog from this forum insisted I check as he experienced similar symptoms with an engine with the same issue. BIG high five to Birddog for his persistence in having me check!

Now at least we've got the problem identified and can work on the solution....will be chatting with Superior first thing Monday morning.

Thanks to all those that provided experence, insight, and encouragement as I worked through a frustrating couple of months!
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Chris Engler, Greene, NY

RV 8 Completed and Flying (N184CE), Showplanes Fastback and Cowl, Barrett IO-360; Dual GRT 10.4 HXr

Kitfox 7; Rotax 914, Built and Sold

VAF donation gladly paid through April 2022
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  #2  
Old 10-21-2017, 09:52 PM
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DaleB DaleB is offline
 
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Location: Omaha, NE (KMLE)
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The "Mystery of the Coughing XP-400"? I'm glad you solved it, but I was just a little disappointed that you didn't have any help from Jupiter, Pete and Bob.
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  #3  
Old 10-22-2017, 02:47 PM
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Janekom Janekom is offline
 
Join Date: Jan 2006
Location: South Africa
Posts: 879
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Phew ! Well done
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  #4  
Old 10-22-2017, 04:04 PM
Kyle Boatright Kyle Boatright is offline
 
Join Date: Aug 2005
Location: Atlanta, GA
Posts: 4,677
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Quote:
Originally Posted by DaleB View Post
The "Mystery of the Coughing XP-400"? I'm glad you solved it, but I was just a little disappointed that you didn't have any help from Jupiter, Pete and Bob.
I love the reference, but I bet only 1/100 RV'ers will get it.

And now I'm off to the airport in my chauffeur driven Rolls...
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  #5  
Old 10-22-2017, 04:46 PM
moosepileit moosepileit is offline
 
Join Date: Dec 2010
Location: Louisville, KY
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Had to google...

The Three Investigators is an American juvenile detective book series first ... as the " three investigators" are three boys named Jupiter Jones, Peter Crenshaw and Bob Andrews.
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  #6  
Old 10-22-2017, 06:42 PM
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Steve Melton Steve Melton is offline
 
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Location: Cincinnati, OH
Posts: 3,529
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how in the heck did that get past the inspector?
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  #7  
Old 10-22-2017, 08:26 PM
Chris Engler Chris Engler is offline
 
Join Date: Aug 2012
Location: Greene, NY
Posts: 86
Default

Quote:
Originally Posted by Steve Melton View Post
how in the heck did that get past the inspector?
Steve - that's the million dollar question. As I noted in one of the previous threads on the topic, my engine was one of 5 "test cell" engines used during the development of the XP-400. The log book that came with the engine shows the following entries (paraphrasing):

1. New engine, test run and in a condition for safe flight

2. 150 hours in the test cell followed by a complete disassembly for inspection and replacement of wear items (bearings and rings). Reassembled in accordance with Superior procedures and work instructions and is in condition for operation.

3. 5 hours in test cell, certification that the engine was manufactured, inspected, and tested in accordance with Superiors Procedures and Work Instructions, and is determined to be in a condition for safe flight.

Each entry of the logbook was signed and certified by Superior.

The one that really has me scratching my head is the last one. My guess is the misalignment of the cam happened during the reassembly following the 150 hours in the test cell...but 5 hours of run time with the cam misaligned and this problem went undetected....I think not!

For those not familiar with the cam to crank alignment, the photo in my first post on this thread shows the cam gear on top aligned with the idler gear (note the "0" with a "dot" on either side). The crankshaft gear is the one on the bottom in the photo. Note that the "0" on both the idler gear and crank gear should align. On my engine, it's clear that the crank is misaligned relative to the cam by one tooth. As a result, the valves are not in the correct position relative to crank (and piston) positions.
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Chris Engler, Greene, NY

RV 8 Completed and Flying (N184CE), Showplanes Fastback and Cowl, Barrett IO-360; Dual GRT 10.4 HXr

Kitfox 7; Rotax 914, Built and Sold

VAF donation gladly paid through April 2022
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  #8  
Old 10-22-2017, 08:38 PM
birddog486 birddog486 is offline
 
Join Date: Mar 2016
Location: Janesville, WI
Posts: 167
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I'm glad you've found the smoking gun Chris. When I read your initial post on your engine problems, it really took me back to all the frustration I went through when I was in the same position.

When you get some time I think it would benefit all the VAF future readers if you put the pic of the cam timing into your other post in case someone has the same symptoms in the future.

BTW my engine with the same problem was a carbed 0-320 on a Cherokee 140.

Travis
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  #9  
Old 10-22-2017, 08:52 PM
Chris Engler Chris Engler is offline
 
Join Date: Aug 2012
Location: Greene, NY
Posts: 86
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Good point Travis....I added a post to the old thread showing the misaligned cam.

Thanks again....would not have found this without your advice! I hope we can catch up in person some day....dinner will be on me!
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Chris Engler, Greene, NY

RV 8 Completed and Flying (N184CE), Showplanes Fastback and Cowl, Barrett IO-360; Dual GRT 10.4 HXr

Kitfox 7; Rotax 914, Built and Sold

VAF donation gladly paid through April 2022
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  #10  
Old 10-22-2017, 09:00 PM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 6,322
Default

Quote:
Originally Posted by Chris Engler View Post
http://tinypic.com/usermedia.php?uo=...c#.Wev41GhSyM8

For those of you that have been following my "XP-400 Still Coughing" thread, I'm delighted to report I had to start a new thread with a different name since the problem has been identified.

After spending 2 months and changing out fuel servos, mags, exhaust, checking plugs, spider, injectors, confirming fuel flow and pressure, etc. etc., and not finding anything, I spent today at the airport, pulled the engine off the airplane, removed the accessory case and there it was....the cam to crank gear train was "one tooth off".

The engine would start and run fine till 2500 RPM then stumble and sputter rich. Leaning would clean up the coughing and allow 2600 RPM static. Many (including the mechanic on our filed) felt the engine would run rough throughout the entire RPM range with the cam timing off but Birddog from this forum insisted I check as he experienced similar symptoms with an engine with the same issue. BIG high five to Birddog for his persistence in having me check!

Now at least we've got the problem identified and can work on the solution....will be chatting with Superior first thing Monday morning.

Thanks to all those that provided experence, insight, and encouragement as I worked through a frustrating couple of months!
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Bill

RV-7
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