REFLECTOR: Still test flying...battling high CHT's (Geoff Gerhardt)

[Geoff Gerhardt]

Fred,

Yes, this is a new engine, so I'm guessing that's part of the reason, but I
don't like having one cylinder being that much higher than the other three.
 I have VG's about where you suggested putting them, an inch or so ahead of
the NACA entrance.  Because I'm having problems primarily on climb out, I'm
thinking I should move them fore a few inches.  Also, the VG's I'm using
are relatively low profile (<1/2" high).  I think I'll make some taller
ones and see if that helps, too.

Thanks for the suggestions.

Geoff

On Mon, Sep 10, 2012 at 9:23 AM, Fred Anderka <fred at holohil.com> wrote:

> Geoff:
>
> Had similar CHT problems with the IO-550, particularly cylinder #2.  There
> are deflector plates between the cylinders that can be bent to change the
> air flow, have not messed with them though.  Trying to put deflectors on
> top of that engine would be a nightmare with all the plumbing that is on
> top of that engine.  Is this is a new engine?  I have been told that the
> CHT's will decrease as the engine breaks in.  This is also a scary portion
> of your flight testing if you follow engine manufacturers reccommendations.
>  The engine manufacturers recommend that for proper break in of the engine
> it should be operated near maximum power for the first 20-25 hours.
>  Continued low power operation will glaze the cylinders resulting in high
> oil consumption.  I suppose 25 hours of touch and go's might qualify.
>
> Place a pair of VG's 1 1/2" ahead of the start of the slope of the NACAs.
>  You will see a dramatic decrease in the CHT's to the point where I am
> trying to figure out a way to reduce the air flow in the winter or when
> flying at very cold altitudes.  Scott suggested making the ramp of the
> NACAs adjustable to reduce the size of the air intake.  The VG's pressurize
> the plenum to a point where I have also noticed an increase in manifold
> pressures during climb out.  The Continental gets it's combustion air from
> the back of the engine plenum.
>
> Fred
> XL-RG (620 hrs.)
>
>
> Date: Sun, 9 Sep 2012 20:08:51 -0400
> From: Geoff Gerhardt <geoff.gerhardt at gmail.com>
> To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
> Subject: REFLECTOR: Still test flying...battling high CHT's
>
> All,
>
> Just an update on my test flying.  I've got just over 9hrs in now.  I have
> been battling high CHT's, making a few changes.  I had a fuel flow
> imbalance that was causing some problems (hot #2) - I think it was a
> partially blocked injector.  I took all the injectors/lines out and cleaned
> them and balanced the flows (mixed and matched injectors until all
> injectors were putting out the same flow.  Now, in cruise, all cylinders
> are pretty close and reasonably cool (or, I guess, not overly hot).  Once I
> get to cruise, they all sit <380F.  But, on climb out, #3 gets way too hot
> (420F) forcing me to reduce power and bring the nose down so I'm climbing
> at <500FPM at ~60% power, 100kts.  But, once I get to cruise and can bring
> the nose down and get the speed up, it behaves.  Still the hottest, but
> it'll sit around 380F.  So, I'm thinking I have to work on my cooling
> plenums.  #4 will get hot too, but it doesn't get much over 400F.
>
> Has anyone had success putting deflectors in the plenums to direct air
> flow to cyls 3/4?  Or, maybe VG's in the entrance of the runners to keep
> the airflow better attached to the bottom of the runner so it can turn the
> corner down to cool 3/4 (I have VG's before the NACAs)?
>
> Part of the issue may be my cruise prop - I need to keep full power on to
> get a decent climb rate.
>
> Thanks.
>
> Geoff
>
> _______________________________________________
> To change your email address, visit
> http://www.tvbf.org/mailman/listinfo/reflector
>
> Visit the gallery!  www.tvbf.org/gallery
> user:pw = tvbf:jamaicangoose
> Check new archives: www.tvbf.org/pipermail
> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.tvbf.org/mailman/private/reflector/attachments/20120910/0a5924a2/attachment.html>