REFLECTOR: Vortex generators location for armpit cooling scoops

[Andrew Ellzey]

Brian'
 
My scoops are what I was told were the standard armpit scoops. Someone here on the reflector gave them to me. They had a Velocity part number sticker on them when they arrived. My kit is a 2005, so it came with the standard NACA down draft scoops. My IO-540 is a true updraft engine. The CHT probes and the factory between cylinder baffles are on the top of the engine. An old photo showing my cylinder baffles is attached. I am considering opening the aft most #5 cylinder head baffle a little wider to see if this would increase the airflow for my #5. The baffling between the cylinders are the actual Lycoming part number units, all other baffling as seen in the photo, I built to seal to my cowling. 
 
I haven't looked at my plugs yet, they were new when I started my ground testing before my first flight test. Since my engine has a fresh overhaul, I hadn't put much credibility into how my plugs are doing, since I don't feel that the rings are seated yet. My #5 EGT is following my high CHT. Again, I have already swapped the #5 fuel injector with the coolest cylinder and the problem didn't follow. I have however seen in the past, a small bit of trash in the fuel flow divider, do this very same thing. I haven't taken the time to take the top off to see if any of the fuel distribution lines are plugged up. It would take some time to set up, but I could also do flow testing to verify that all cylinders are getting the same amount of fuel, without taking the top off of my flow divider, and possibly damaging the internal diaphragm.  
 
Andy Ellzey


>________________________________
> From: Brian Michalk <michalk at awpi.com>
>To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org> 
>Sent: Wednesday, August 14, 2013 4:28 PM
>Subject: Re: REFLECTOR: Vortex generators location for armpit cooling scoops
>  
>
>
>I am running armpit scoops, but mine are variable.
>
>I have been battling high temps too, and decided to stop flight
      testing until the weather cools off.  I'm just not able to get
      much testing in to adjust variables to see the effects.
>
>Unfortunately on my last flight I broke my rule and changed two
      variables at the same time.  Before flight I opened up the scoops,
      and advanced timing.  The result is that my #5 CHT was at
      redline.  The good news is that oil temps were down.
>
>Your scoops are pretty big, and should work.  Have you looked at
      your plugs to see if you've got mixture/airflow or detonation
      problems?  EGT shows normal for #5?  Maybe compare the #3 and #5
      plug.  The top ones.  Do you have the baffles installed under the
      cylinders, or does the updraft have baffles over the top?  It's
      the baffles that go between the cylinders to force air through the
      fins.
>
>On 8/14/2013 3:50 PM, Andrew Ellzey wrote:
> 
>I am still battling a high CHT at cruse on my # 5 cylinder on my updraft IO-540-E1A5, 300HP Lycoming engine. I can do full power climb outs in the pattern all day without any issue. From everything that I have read on this subject on the Reflector, this is common with the arm pit cooling.  The higher pitch angle in the pattern, and in a cruse climb, forces plenty of cooling air into the scoops, but the cooling ability drops off in level cruse fight attitudes. My question is, is there anyone left on the reflector that is using the armpit cooling, and do you have vortex generators in front of your armpit scoops to help the airflow boundary layer adhesion to this area forward of the armpit scoops? If you have vortex generators, what size, location, did you make them, buy them, can you send a photo, please. 
>>
>>I have swapped and calibrated my CHT probes, swapped the lowest CHT cylinder fuel injector with my #5 injector. Nothing helps, it seems to be tied with airflow into my scoops, or airflow inside my lower cowling. If the addition of vortex generators doesn’t  help, I will probably have to install some additional baffling to redirect more air to the aft two cylinders, #5, and #6. Cylinders 1, 2, 3, and 4 are getting plenty of air, in fact they are running cooler than I like at this time, but until I can get #5 CHT under control, I can’t lean my engine properly to know if I have adequate airflow for all cylinders or not. Installing my gear doors seemed to help. 
>>
>>Photo attached showing my armpit cooling scoops. The additional screws under the armpit scoops, attaches a mating internal scoop that directs the airflow to my aft lower cowling.   
>>
>>Thanks again for your help, 
>>-----------------------------------------
>>Andrew Ellzey
>>N151AJ 10 hours into Phase 1 testing   
>> 
>>
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