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If you were able to get your temps to exceed 200 F during sea level to
12k ft climb, then we would know you need to focus on airflow thru
radiators. That's it!
Improving cooling is tough, but now we have this simple test to prove
whether it's air flow issue.
Your trapped air test works great for air in rad. What about if high
point is block? My test for that is to heat soak the engine, then shut it
off. I can hear a thump thump from local boiling.
I changed my cooling sys until I reached the point I could drain all the
coolant, then refill. Able to get every drop to go back in without
fussing with anything. That's when I knew I had effective dynamic air
bleed. Another big safety advantage.
Pretty interesting we both found exit ducting a negative. I was quite
surprised to find better cooling by allowing rad exit air to wander
around the engine compartment. I agree, it might be because I had less
than optimal duct design.
-al wick
Artificial intelligence in cockpit, Cozy IV powered by stock Subaru 2.5
N9032U 200+ hours on engine/airframe from Portland, Oregon
Prop construct, Subaru install, Risk assessment, Glass panel design info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html
On Sun, 5 Feb 2006 11:28:53 -0500 "Ed Anderson"
<eanderson@carolina.rr.com> writes:
> Thanks, Al. Another Data point.
>
> Most of us using the two GM cores for radiators have approx 650
> cubic inch
> of core volume and 200 sq inch of core frontal area. I normally fly
> cruise
> at 7.5 GPH and my coolant and oil temps are between 165F and 185F
> depending
> on OAT. Right after take off both may hit 200F until airspeed
> builds up but
> I am burning between 16-18 GPH during take off and initial climb
> out.
>
> I agree that trapped air is a very significant (and often
> undiagnosed)
> problem area. Tracy Crook showed me a very simply way to tell. Run
> your
> engine until you reach an operating temperature (>120F) then place
> your hand
> on the side tank of the radiator (assuming its mounted more or less
>
> vertically), if you have air trapped, there will be a definite and
> sharp
> change in temperature of the metal of the side tank to the touch
> between the
> air and coolant level - cooler where the air is trapped at the top.
> It
> normally takes me 3 runs to 5000 rpm (while watching the coolant
> temps)
> before I have most of the air out. Now, if I had been smart enough
> to have
> put in a air bleed in the top of my cores as you suggest it would
> have been
> easy to get rid of the trapped air.
>
> Early on when I was dealing with cooling problems, I made fiberglass
> exit
> ducts for the two radiators and found that they hindered cooling -
> but, I
> had to compromise the ducts passages significantly to simply fit
> them under
> the cowl - so probably not a valid test.
>
> Cooling is certainly an area where small details can make a big
> difference
> and symptoms are often difficult to trace to the underlying cause.
> So much
> interaction and one thing affecting several parameters so which one
> fixed
> the problem, etc.
>
> Fortunately, my cooling problems are in the past. The most
> significant
> thing I did for the rotary was to move the oil cooler up under the
> prop
> spinner where it got plenty of air flow. That dropped my oil temps
> by 30-40F
> which in turn brought down my coolant temps and all was well.
>
> One last thing, is sometimes a cooling problem could indicate a good
> thing.
> I noticed that each time my engine power production went up as a
> result of
> intake/exhaust experimenting, that my temps also went up a bit.
> Fortunately, applying the StreamLine ducting to my intakes improved
>
> airflow/pressure recovery sufficiently to deal with the increased
> heat
> rejection required.
>
>
> Ed
>
> Ed Anderson
> Rv-6A N494BW Rotary Powered
> Matthews, NC
> eanderson@carolina.rr.com
> ----- Original Message -----
> From: "al p wick" <alwick@juno.com>
> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> Sent: Sunday, February 05, 2006 10:14 AM
> Subject: [FlyRotary] Re: NPG Coolant Temperature vs 50/50
>
>
> > <Cavitation theory:
> > Don't forget, I operate same engine as EGG, totally stock. With
> none of
> > the cooling issues. I think that eliminates cavitation as
> explanation.
> >
> > Here's what I think it's all about....
> >
> > Problem: You'd like better cooling, but are unsure about what's
> causing
> > marginal cooling.
> > Test: Compare to my performance to prove that it's air flow thru
> > radiator.
> > Method:
> > a) Measure your radiator fin area in Cubic Inches. If more than
> 408 C.I.
> > proceed.
> > b) Operate engine, place hand all over radiator to verify no
> trapped air
> > pockets.
> > c) Determine 7.4 gph throttle setting. This makes your power
> output same
> > as mine.
> > d) Warm up engine (heat soak it, don't just get it warm).
> > e) perform climb test with throttle at 7.4 gph setting. Take off
> at sea
> > level, climb to 12k ft.
> >
> > If coolant temp raises during the climb, you clearly have air
> flow
> > problem thru radiator. Test different air flow concepts.
> >
> > Notes:
> > -My testing found trapped air in cooling system is 10 times more
> > significant than any other factor. Install dynamic air bleed to
> make sure
> > you are free of air.
> > -I have no oil cooler, so if your temp rises during climb, you
> have very
> > significant air flow problem.
> > -I have no rad air exit ducting. I found it aggravated my cooling.
> Even
> > though all the articles you read say the opposite. So don't make
> > assumptions.
> >
> > I suspect this test can really help.
> >
> >
> > -al wick
> > Artificial intelligence in cockpit, Cozy IV powered by stock
> Subaru 2.5
> > N9032U 200+ hours on engine/airframe from Portland, Oregon
> > Prop construct, Subaru install, Risk assessment, Glass panel
> design info:
> > http://www.maddyhome.com/canardpages/pages/alwick/index.html
> >
> >
> > On Sat, 04 Feb 2006 21:05:11 -0500 Chad Robinson
> <crj@lucubration.com>
> > writes:
> >> Ed Anderson wrote:
> >> > Delta T = Q/cM, now if the combined effects of c and m
> provide
> >> 13% less
> >> > heat transfer capability than the 50/50 mixture that would
> >> indicated
> >> > that to carry away the same Q at the same flow rate, the delta
> T
> >> of NPG+
> >> > would need to increase by 13%. So if I were getting 180F with
> the
> >> 50/50
> >> > for the same Q load (and flow rate) then with NPG+, I would
> >> expect 180
> >> > *1.13 = 203F. Yet, if I understood correct we have reports
> that
> >> lesser
> >> > temperatures results noted by users of NPG - this leaves me a
> bit
> >> puzzled.
> >>
> >> I don't have the answer, but how about a hypothesis? Suppose
> they
> >> have a
> >> cavitation problem. A more viscous fluid tends to reduce the
> onset
> >> of
> >> cavitation, no? And is there any data on what pressure their
> system
> >> is being
> >> run at?
> >>
> >> Regards,
> >> Chad
> >>
> >
> > --
> > Homepage: http://www.flyrotary.com/
> > Archive and UnSub:
> http://mail.lancaironline.net/lists/flyrotary/
> >
>
>
>
> --
> Homepage: http://www.flyrotary.com/
> Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/
>
>
-al wick
Artificial intelligence in cockpit, Cozy IV powered by stock Subaru 2.5
N9032U 200+ hours on engine/airframe from Portland, Oregon
Prop construct, Subaru install, Risk assessment, Glass panel design info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html
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