REFLECTOR: Still test flying...battling high CHT's

[Darrell & Nora Kufalk]

How many hours on your engine?  New cylinders run hot during break in.  

Also read this starting on page 4 third column halfway down.  Duane Swing
talks about VGs and CHTs.  
http://www.velocityaircraft.com/views/v29.pdf

For what it's worth, I tested 1/4" tall VGs in front of my NACAs and got
exactly ZERO degrees in cooling reduction.

Darrell


-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Richard J. Gentil
Sent: Sunday, September 09, 2012 8:40 PM
To: geoff.gerhardt at gmail.com; Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Still test flying...battling high CHT's

Hi Geoff,

My deflectors inside the plenum did nothing but the VG's in front of the
NACA's helped. I have not tried inside the runners. 

Richard 

Sent from my iPhone 4 Classic

On Sep 9, 2012, at 8:08 PM, Geoff Gerhardt <geoff.gerhardt at gmail.com> wrote:

> 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
> 
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