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rough running during taxi after landing

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rv8a2001(at)yahoo.com
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Posted: Wed Jun 13, 2012 11:06 am Post subject: rough running during taxi after landing

Same problem here, its fuel boiling in the injector lines. Call AFP and order he smallest injector jets, this will raise the line pressure thus the boiling point. Also set your system to an extra rich idle mixture just for this occasion. Mine really acts up on left turns......go figure.

 

  

 Scott RV-8a

    

From: thomas sargent <sarg314(at)gmail.com>

To: rv-list <rv-list(at)matronics.com> 

Sent: Wednesday, June 13, 2012 11:15 AM

Subject: RV-List: rough running during taxi after landing

 This is a question for all of you who have AirFlow Performance fuel injection, as I do on mt RV-6A.  When I start up and taxi around prior to take off, I have no problem, even in warm Arizona weather.  However, after I've been flying and return to land, taxiing is a problem.  The engine runs very unevenly and almost stops completely some times.  



The guys at AFP, and I think they are right, say it is fuel vaporizing in the skinny stainless steel lines that go from the spider to the injector nozzles.  "These planes do that."  I notice on a warm day when I hit the brakes to slow down for a turn, it always gets worse, as though the slight decrease in air moving through the cowl aggravates the vaporization.  Turning on the boost pump has no effect.



I should mention that I have a fiberglass cooling plenum which means there is a bit less enclosed volume over the engine than there would be  if I'd use the stock baffling scheme that has the airseal fabric pressing against the top of the cowl.  



I one time had the thing stop completely as I was turning off the runway and heard the tower advise the next aircraft to go around.  Embarassing, but at least, I can always restart the engine quickly.  If the fuel flow is a bit higher than you'd use for taxi, the engine smooths out - also consistent with fuel vaporization.

Does anybody else have this same problem?

-- 

Tom Sargent, RV-6A  N811WT



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sarg314(at)gmail.com
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Posted: Wed Jun 13, 2012 11:26 am Post subject: rough running during taxi after landing

Scott:

Yes!  Left turns are definitely worse.



On Wed, Jun 13, 2012 at 12:05 PM, scott bilinski <rv8a2001(at)yahoo.com (rv8a2001(at)yahoo.com)> wrote:

  	  Quote: 	
		  Same problem here, its fuel boiling in the injector lines. Call AFP and order he smallest injector jets, this will raise the line pressure thus the boiling point. Also set your system to an extra rich idle mixture just for this occasion. Mine really acts up on left turns.......go figure.

 

 

  

 Scott RV-8a

    





 	


-- 

Tom Sargent

  [quote][b]

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recapen(at)earthlink.net
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Posted: Wed Jun 13, 2012 11:33 am Post subject: rough running during taxi after landing

Tom,



I had a sorta-similar problem - mine was more restart related though.



I would land - taxi - refuel - and have trouble restarting...even after using the purge valve...and it would run a bit rough...

I changed my injector restrictors from the stock .028 to .024 which helped a lot - and allows the boost pump to manage the stumbling at idle after the restart. My next step will be (already have the part) to put a cooling shroud on the mechanical pump....I already know it will be a PITB to install.



I have the SamJames plenum and cowl along with the AFP injection - mine is updraft as I have a Vetterman dual crossover with mufflers and heater-boxes.



Haven't had these kinds of issues since and I am quite happy with the results.



Ralph



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recapen(at)earthlink.net
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Posted: Wed Jun 13, 2012 12:07 pm Post subject: rough running during taxi after landing

Tom,



Do you have the SJ cowl and plenum or did you go plenum only?

With my setup, I am experiencing some balance problems with my injection system from front to rear when I try to run Lean-of-peak (LOP).  AFP has recommended that I install turbo-style injector vent rails to balance the vent-pressure at the base of each injector.  Another item that I have the parts for and will do in the future.



Collect all the performance data you can - in case you decide to go with .022's.  I think .022 is the smallest size available.



Have you run the flaw balance tests yet for LOP operations?  What do you have for an engine monitor?  Mine is an AFS3400sEE - I get data captured at one second intervals for all of my flights.



Keep us informed - I'll let you know what I did...and want to know your results as well.



Ralph

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sarg314(at)gmail.com
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Posted: Wed Jun 13, 2012 12:55 pm Post subject: rough running during taxi after landing

Ralph:

I don't have the Sam James stuff. I have a stock cowl with a cooling plenum I built myself.  I haven't done any flow testing.  If I get to altitude and lean it most of the way (say 9.5gph at 8500 ft and 2400 rpm) and let things stabilize for a few minutes, then I can lean it.  I have an old VM1000 and use it's leaning mode.  It looks for peak egt as I slowly lean it.  It usually ends up at 8.0 or 8.5 gph when leaned to 50deg. rich of peak an 2400 - 2450rpm.

 

My cyl. head temps are pretty even. The VM1000 temp. bar graph shows cyl. 2,3, and 4 at the same level and cyl #1 one notch lower than the rest.  So I think that means my fuel flow is pretty even to all the cylinders.

 

On Wed, Jun 13, 2012 at 1:06 PM, Ralph E. Capen <recapen(at)earthlink.net (recapen(at)earthlink.net)> wrote:

 	  Quote: 	
		   --> RV-List message posted by: "Ralph E. Capen" <recapen(at)earthlink.net (recapen(at)earthlink.net)>

 

 Tom,

 

 

Do you have the SJ cowl and plenum or did you go plenum only?

 With my setup, I am experiencing some balance problems with my injection system from front to rear when I try to run Lean-of-peak (LOP).  AFP has recommended that I install turbo-style injector vent rails to balance the vent-pressure at the base of each injector.  Another item that I have the parts for and will do in the future.

  

 Collect all the performance data you can - in case you decide to go with .022's.  I think .022 is the smallest size available.

 

 Have you run the flaw balance tests yet for LOP operations?  What do you have for an engine monitor?  Mine is an AFS3400sEE - I get data captured at one second intervals for all of my flights.

 

 Keep us informed - I'll let you know what I did...and want to know your results as well.

 

 Ralph





	




-- 

Tom Sargent

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recapen(at)earthlink.net
Guest

Posted: Wed Jun 13, 2012 2:38 pm Post subject: rough running during taxi after landing

 	  Quote: 	
		  From that - it sounds like you're in pretty good shape.


	


If you want to get to the really finer points of LOP, you'll need to record fuel flows and egts for when each cylinder peaks.  Then, you'll be able to determine if the flow rates are within .1gph of each other...(that's where mine are).



Good luck,

Ralph

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panamared505(at)brier.net
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Posted: Thu Jun 14, 2012 7:09 am Post subject: rough running during taxi after landing

YEP.  Exact same problem.  

  

 Keep the boost pump on and the RPMs above  1000.  Install a fuel pump cooling shroud.  

  

 On hot days, the problem does not go  away, just have to learn to manage it.

  

 Bob

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