REFLECTOR: Vortex generators location for armpit cooling scoops

Thu Aug 15 07:58:49 CDT 2013

Andy,

You say you have been doing some leaning, but have not gone to LOP.  Doing
"some" leaning can put you at the hottest part of the mixture curve.  You
will see dramatically lower temperatures when running LOP at cruise.  I
always run LOP, both for fuel economy and cooling.  There's a great webinar
on the EAA website by Mike Busch that covers leaning.  For max cooling,
either run full rich or LOP.  A little leaning will put you right into peak
or either side of it which will run high CHT's.

The only time I have CHT issues now is during the climbout.  Between
~3000-5000' is where I have to be careful on a hot day to keep the speed up
and power down to 70%.  Once I get past ~5000', I can go back to WOT and
100kt climb and everything's fine.

Regarding hot cylinders, you can tell if its a mixture issue (i.e. clogged
injector, leaky intake) by leaning out and seeing where each cylinder
peaks.  If one peaks way early/late, it has a mixture issue.  Otherwise, it
might just be a cooling airflow issue.  If you are using a Dynon Skyview or
other EFIS, the savvyanalysis.com website is a great tool to diagnose
engine issues - it lets you upload your data log and has a bunch of tools
for analysing CHT, EGT and fuel flow data.

Take all that with a grain of salt, tho, I'm certainly no expert but have
had CHT issues early on and learned how to diagnose/deal with them.

Geoff

On Wed, Aug 14, 2013 at 11:31 PM, Andrew Ellzey <ajlz72756 at yahoo.com> wrote:

> Scott
>
> I haven't done any air flow testing yet. On a Lycoming the #5 & 6 are aft
> most cylinders on the engine, which is forward most cylinders on our
> Velocities. CylinderI have been leaning some just to keep from burning 20
> gal per hour. But I haven't tried any LOP operation. At 6,000 feet, running
> 24/24 I have been able to barely keep #5 under 450 degrees, my preset
> redline on my EFIS display, and fuel flow of 16 gal per hour. # 6 at these
> settings will be running about 400 to 425 degrees. All other cylinders are
> under 400 degrees, more in the ranges of 375 to 385 degrees.
>
> Andy
>
>    *From:* Scott Derrick <scott at tnstaafl.net>
>
> *To:* Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
> *Sent:* Wednesday, August 14, 2013 5:53 PM
>
> *Subject:* Re: REFLECTOR: Vortex generators location for armpit cooling
> scoops
>
>  have you done a flow test to see where the air is going?
>
> sprinkle some used(dark) motor oil around the scoops, be generous.
>
> fly in cruise for a couple minutes, land and inspect.
>
> Is #5 forward or rear in a Lycoming?  #5 on Cont. is rear. Rear meaning
> closest to prop.  I had my forwared cylinders run warmer than the others at
> first.  I have two deflectors in side my plenum on both, which helped.
>
> Somebody suggested attempting to run LOP and map out the peaks for each
> cylinder, a good idea.  Climb up to 8,000 ft to do it so you don't have to
> worry about detonation around the 50ROP danger zone.  Allow you to play
> around slowly with the mixture.  Keep an eye on redline egt of course.
>
> Scott
>
> -------- Original Message --------
> Subject: Re: REFLECTOR: Vortex generators location for armpit cooling
> scoops
> From: Brent mailto:bjb3013 at yahoo.com <bjb3013 at yahoo.com>
> To: Velocity Aircraft Owners and Builders list mailto:reflector at tvbf.org<reflector at tvbf.org>
> Date: 08/14/2013 04:07 PM
>
> Have you tried a inflight LOP test and figure which cylinders peak when?
> How about swap the injector from your coolest cylinder to #5
> Not sure what VGs are going to accomplish if some cylinders are too cool
> already.
>
>  Brent
> N61VB
> Std RG
>
> Sent from my iPad 5
>
>
> On Aug 14, 2013, at 3:50 PM, "Andrew Ellzey" <ajlz72756 at yahoo.com> 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
>
>  <DSCN7120a.jpg>
>
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