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  #41  
Old 10-17-2017, 08:32 AM
BillL BillL is online now
 
Join Date: Sep 2007
Location: Central IL
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Quote:
Originally Posted by Chris Engler View Post
Following up on the information provided by Birddog and Larry yesterday, I stopped by the airport yesterday evening and ran through the procedure Birddog described. My conclusion was there was a problem with cam alignment.

When I return home later this week, I'll begin the process of engine removal and getting it prepped for transport/rework.

I spoke with Superior this afternoon and at least preliminarily, documentation at their shop of the 5 hours of run time following the ring/bearing replacement (i.e., second build) is not readily available but they will continue to search.
Chris, good to see you are going to send it back. Lets say your measurements are perfect -the cam is off. It does not explain the symptoms. If, however, there are torsional problems due to, say a loose crank gear, then the static cam timing could be off and going absolutely crazy as the rpm increases affecting both ignition and cam events. Please post the final answers when concluded. Hope they check the crank for issues as well.
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Last edited by BillL : 10-17-2017 at 08:34 AM.
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  #42  
Old 10-17-2017, 08:57 AM
bnt83 bnt83 is offline
 
Join Date: Sep 2014
Location: Lincoln NE
Posts: 55
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Anyone mentioned bad valve spring yet? This happened on an O-300 they spent lots and lots of money fighting a similar issue intermittent stumbling at full power usually after just getting good and warmed up on departure climb. After lots of wasted hours and money they took all the valve springs off and measured them and they did not meet spec.
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  #43  
Old 10-17-2017, 07:40 PM
Chris Engler Chris Engler is offline
 
Join Date: Aug 2012
Location: Greene, NY
Posts: 52
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Bill - I'm not an expert by any means when it comes to the inner working of aircraft engines but Birddog experienced the same symptoms I'm having and it turned out his cam gear was a tooth off. From my from discussions with Superior yesterday, they indicated they've seen a cam gear a tooth off and the engine started fine and ran fine until the top of the RPM range when it simply wouldn't reach expected RPM and wouldn't make full power (though no coughing/stumbling in their case). They didn't indicate if their motor was carbed or fuel injected. Perhaps the fuel injected motors will cough rich in this condition and the carbed motors don't ? The symptoms coupled with the incorrect rocker geometry on cylinder 2 at TDC indicates that the cam is off a tooth on my motor. Weather that's the only problem remains to be seen but my engine is very predictable in terms of symptoms and exactly what RPM they present so I'm guessing once we have the cam alignment set correctly all will be well. The engine will be sent to either Superior themselves or one of their authorized shops for a thorough evaluation/repair followed by time in a test cell at all ranges of operation.

BNT83 - thanks for the tip on the valve springs - definitely add that to the list of things for the shop to confirm!

More details to follow....
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RV 8 Under Construction (N184CE Reserved), Showplanes Fastback, Superior IO 400; Dual 10.4 HXr

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  #44  
Old 10-18-2017, 06:11 AM
trifield trifield is offline
 
Join Date: Apr 2006
Location: melbourne australia
Posts: 9
Default Vacuum

Idle vacuum will tell you if the cam timing is out
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  #45  
Old 10-20-2017, 12:00 AM
PCHunt PCHunt is offline
 
Join Date: Feb 2007
Location: San Diego, CA
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Quote:
Originally Posted by trifield View Post
Idle vacuum will tell you if the cam timing is out
Interesting thought. Could you provide more details, please. Idle mixture can also affect Manifold Pressure (vacuum) at idle.

What would you look for?

Thanks,
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  #46  
Old 10-22-2017, 08:48 PM
Chris Engler Chris Engler is offline
 
Join Date: Aug 2012
Location: Greene, NY
Posts: 52
Default Root Cause Identified!

http://tinypic.com/usermedia.php?uo=...c#.We1Ja2hSyM8

As it turns out, the problem is the result of incorrect cam to crank timing! For those not familiar with the cam to crank alignment, the photo above 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 Under Construction (N184CE Reserved), Showplanes Fastback, Superior IO 400; Dual 10.4 HXr

Kitfox 7; Rotax 914, Built and Sold

VAF donation gladly paid through July 2018
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  #47  
Old 10-22-2017, 09:30 PM
BillL BillL is online now
 
Join Date: Sep 2007
Location: Central IL
Posts: 3,993
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Quote:
Originally Posted by Chris Engler View Post
http://tinypic.com/usermedia.php?uo=...c#.We1Ja2hSyM8

As it turns out, the problem is the result of incorrect cam to crank timing! For those not familiar with the cam to crank alignment, the photo above 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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Bill

W&B done
Doing paperwork.
Beginning G3X calibrations.
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