REFLECTOR:Oil temps and heating

Dave Nelson reflector@tvbf.org
Fri, 24 Oct 2003 18:52:56 -0500


Hi, Scott

Thanks for taking the time to write.  In answer to your question, no,
unfortunately, I'm
pretty certain that my CHTs are about where they were.  I keep a pretty good
eye on them.
They typically max out at about 190 - 200 C (374 - 392F) in a steady climb.

My background includes about 900 hours in a updraft cooled Varieze which I
built.  I agree
that even small leaks cause big problems.

In this case, it seems like the fact that I've basically eliminated all
airflow around the accessory case
has got to be related to the oil temps... but, I'm seeking out opinions,
such as yours,
which I really do value.  Thanks!

Dave
----- Original Message ----- 
From: "Scott" <scott@tnstaafl.net>
To: <reflector@tvbf.org>
Sent: Thursday, October 23, 2003 10:10 PM
Subject: Re: REFLECTOR:Oil temps and heating


> Dave,
>
> Are you sure your CHT's aren't a bit higher now than they were before the
> mods you made?
>
> I slight rise in CHT's can make a huge difference in your oil temps, I'd
> say 80+% of your oil temps come from cooling the cylinder-head assemblies.
>
> Its possible a 10 degree rise in cyl head temps can give you a lot more
> than a corresponding 10 degree rise in oil temps.
>
> I just went though(well I'm not totally done, are we ever?)  a cowl
> modification which included tightening up the air leaks in the engine
> compartment.  I also have the standard single nose mounted oil cooler, and
> updraft cooling from armpit scoops. I used to be in the cooling-challenged
> position you are in now.  I could get my oil in the 240's pretty easy, and
> during the summer could not run at max RPM or I would over heat.
>
> Now  with 80% of the air leaks fixed I haven't seen oil temps above 220
> after a 10,000 ft steady climb and I cruise at max rpm with oil temp
around
> 205F.
>
> I've been told that most cooling problems are a direct result of poor
> baffling, and in my case it was completely true.
>
> Scott
>
> At 08:23 PM 10/23/2003, you wrote:
> >I'm fairly new to the reflector,  so I apologise if this subject has been
> >covered before.  I guess I'd be a bit surprised if it hadn't...
> >
> >I've just passed 600 hours on my STD-RG, which I built.  I live in
> >Minnesota, and winters are long up here, so I always search for good
> >projects to upgrade my aircraft over those long winter months.  Last
> >winter I decided to clean up the lower cowl in order to improve speed &
> >performance.... you see, my hangar mate is a beautiful Cozy 3 place.
With
> >his 150 horses, he's close (way too close) to keeping up with me in my
> >IO-360 powered, 200 HP velocity RG.  It's always a race when we go
flying...
> >
> >My plan was to do drag reduction to the lower cowl by reworking the
armpit
> >scoops I use for cooling air and eliminating the induction air scoop.  My
> >airplane's been flying for quite awhile now, so I'm sure you guys and the
> >factory have come up with 50 better solutions than what use to have...
> >which was the factory standard scoops mounted on the cowl, and separate
> >"inner" scoops that were mounted to the sides of the fuselage and ducted
> >cooling air to the plenum.  I orignally made the inner/outer scoop
> >combination to make it easy to remove the lower cowl without having to
> >muck with anything.  It worked well, but there was quite a gap required
> >between the inner fuselage mounted scoops and the cowling.
> >
> >I figured I could reduce the total scoop size by about 25% and improve
> >cooling in the process by getting rid of the gap.  Cooling would be
> >improved given that high pressure air was leaking into the lower engine
> >area through the gap... by tightening up the outer scoop I would actually
> >increase the differential pressure between the plenum and the lower
engine
> >area, and also reduce overall drag.  At least that was the theory.  So, I
> >reworked the whole system - I made smaller armpit scoops that are mounted
> >to the fuselage, and reformed the cowl to fit tight against the new
> >scoops.  I faired the new scoops into the cowl so that the airflow stays
> >attached as long as possible.  Additionally, I made a small plenum that
> >provides both engine induction air and cooling air from the right hand
> >armpit scoop, thereby eliminating the drag from the separate induction
air
> >scoop.
> >
> >Results from all this work are very mixed... my speed didn't increase at
> >all despite the drag reductions.  You may laugh at my stupidity on this,
> >but I neglected the fact that by not separating the air in the new small
> >cooling/induction air plenum, I lost the ram air effect on the induction
> >air side.  I lost about 1.5 inches of maximum manifold pressure because I
> >didn't separate the induction air from the cooling air on the right
> >scoop.  Alas, a project for this winter.  The real problem, though, has
> >been that with this new setup, my oil temps have become very difficult to
> >manage.
> >
> > From a cooling perspective, I've got the standard nose mounted oil
cooler
> > and cabin heat system.  Before the modification, my oil temps rarely got
> > up to 100 C (212 F), and my CHTs were all around 350 F +/- 25 degrees.
> > Now, in a climb I can easily heat the oil to redline (242 F) if I'm not
> > careful.  After much thought and work, it appears that the leakage air
> > that was slipping between the inner and outer armpit scoops and
> > pressurizing the lower cowl also had a cooling effect on the accessory
> > case, oil sump, and the oil temperature transducer.  Tightening up the
> > cowl, eliminating the "blow by". Reducing the size of the armpit scoops
> > did not change the CHTs, but because I lost the airflow over the bottom
> > engine and accessory case, my oil temps are now a problem.
> >
> >So, here are two questions for the reflector crowd:
> >
> >1) How much, if any, cooling air is required for the accessory case and
> >oil sump?  It's logical that you'd want some, but, OTOH any air down
there
> >reduces the differential pressure from the plenum / top of the engine to
> >the bottom... thereby potentially increasing CHTs.  Thoughts?  BTW, just
> >to get the discussion going, I discussed this extensively with the
> >Lycoming rep at OSH, who told me that he didn't think I needed any
airflow
> >over the sump/accessory case...
> >
> >2) My cabin heat box is the original, and I've always been unhappy with
> >the push/pull cable for the babin heat flapper valve.  Anyone put in a
> >electrically actuated flapper valve?
> >
> >To anyone who's acutally read this far... THANKS!
> >
> >Dave
> >600+ hours STD-RG N22DN
> >
> >----- Original Message -----
> >From: <mailto:romott@adelphia.net>Ronnie Brown
> >To: <mailto:reflector@tvbf.org>reflector@tvbf.org
> >Sent: Thursday, October 23, 2003 2:02 PM
> >Subject: Re: REFLECTOR:Heating
> >
> >I was considering installing electric seat heaters but I decided to try a
> >google search for 12vdc electric blankets and look what I
> >found!
>
><http://www.baproducts.com/rphb1101.htm>http://www.baproducts.com/rphb1101.
htm
> >
> >Ronnie
> >----- Original Message -----
> >From: <mailto:cdwoolston@earthlink.net>Craig and/or Denise Woolston
> >To: <mailto:reflector@tvbf.org>reflector@tvbf.org
> >Sent: Wednesday, October 22, 2003 1:20 AM
> >Subject: RE: REFLECTOR:Heating
> >
> >Well I went way overboard but it was one of those great ideas that
quickly
> >multipled in to lots of hours and it's still not done...
> >
> >I made two plenums that will mount on canard bulkhead.  They each have a
> >hot and a cold source coming from front oil cooler and fresh air NACA
> >respectively.  Since the wife and I are never the same temperature a
small
> >diverter flap inside each plenum allows for individual temperature
> >control.  I plan to drill two holes in canard bulkhead that each plenum
> >sits over the top.  One hole will just allow the output to blow down on
> >feet and the other will be routed to the instrument panel eyeball
> >vent.  Time will only tell if it will work.  As for the rear seats I'm
> >thinking seriously about electric seat warmers and/or electric blanket
outlet.
> >
> >Craig
> >
> >!----------------------------!
> >! Craig Woolston             !
> >! XL-FG in Palmdale, CA      !
> >! cdwoolston@earthlink.net   !
> >!----------------------------!
> >-----Original Message-----
> >From: reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org]On Behalf
> >Of velocityxlfg
> >Sent: Monday, October 20, 2003 9:07 AM
> >To: reflector@tvbf.org
> >Subject: REFLECTOR:Heating
> >
> >Can some one send me some pictures of what they did on there heating
> >system. ducts, Heat exchanger routing of the
> >heat ducts.   Ect.
> >Ron
> ><mailto:velocityxl@fastmail.fm>velocityxl@fastmail.fm
>
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