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

[Geoff Gerhardt]

Oh, and yes, my engine is freshly rebuilt - new tight cylinders, so that's
a contributor, too, I've heard.

On Sun, Sep 9, 2012 at 11:08 PM, Darrell & Nora Kufalk <kufalk at wi.rr.com>wrote:

> 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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