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View Poll Results: Do you remove cabin Heat in Summer & Does it Help Engine Cooling -multi selections OK
You remove cabin heat during summer 5 11.36%
You note improved engine cooling when cabin heat removed 1 2.27%
You assume improved engine cooling by not dumping high pressure air in lower cowl? 1 2.27%
Does not matter/don't care, leave cabin heat installed year round 37 84.09%
Voters: 44. You may not vote on this poll

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  #11  
Old 05-23-2020, 10:22 AM
Toobuilder's Avatar
Toobuilder Toobuilder is offline
 
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Quote:
Originally Posted by gmcjetpilot View Post
... My BMW R1150RT motorcycle has heated grips and outlets for heated suits (never used that). Looking at amazon a nice 12v 90w heated motorcycle jacket, draw is 90/12 ~ 7.5 amps...
Also based on my motorcycle experience, I've seen that if you can keep your core warm (vest), it makes the rest of the body relatively easy to manage. I also have heated insoles, but have never used them. The firewall throws off just enough heat that I don't need them. My wife sitting in back with her feet against the fuselage skin, DOES use the insoles.

The vests and insoles are lighter than the heat muffs and ducting they replace, and they can be left in the closet until needed.
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  #12  
Old 05-23-2020, 10:34 AM
Tom Martin Tom Martin is offline
 
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You are supposed to inspect and or remove the heat muff system annually. I remove mine in the late spring, inspect things, and then install it in fall
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  #13  
Old 05-23-2020, 05:01 PM
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Walt Walt is offline
 
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Quote:
Originally Posted by Tom Martin View Post
You are supposed to inspect and or remove the heat muff system annually. I remove mine in the late spring, inspect things, and then install it in fall
Just my opinion but I don't think the typical Van's heat shroud (which just covers a piece of pipe) falls into the same inspection category as a typical muffler with a heat shroud like found on most certified aircraft.
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  #14  
Old 05-23-2020, 05:08 PM
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N941WR N941WR is offline
 
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You missed an answer that says, "No - I don't have a CHT issue."
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  #15  
Old 05-23-2020, 07:35 PM
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Toobuilder Toobuilder is offline
 
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Hyperbole aside, the cabin heat system most certainly does bleed off cooling capacity. Even when "turned off", the typical heat muff still ports a significant volume of otherwise valuable cooling air overboard with no benefit.

That significant amount of wasted CFM could be used to bring cooling under control OR reduce airframe drag (by reducing airflow through the cowl).
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  #16  
Old 05-24-2020, 04:09 AM
Tom Martin Tom Martin is offline
 
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Michael is spot on regarding the extra cooling air lost with a heat muff system that is installed but not needed for cabin heat.
Many folks have spent hours and hours of work sealing plenum systems so that no cooling air is lost. Then when your cabin does not need heat you are effectively introducing a 2” hole into your upper plenum.
No problem in the winter, but in the summer it would be nice to have that extra cooling air.
When you close your cabin heat valve, that now heated air, is dumped into firewall area.
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  #17  
Old 05-24-2020, 04:23 AM
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plehrke plehrke is offline
 
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Quote:
Originally Posted by N941WR View Post
You missed an answer that says, "No - I don't have a CHT issue."
Same.

Plenty of summer cooling as I have a good baffle sealing. YMMV depending on where you fly.
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  #18  
Old 05-24-2020, 05:32 AM
BillL BillL is offline
 
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Default It is a system, what do you really want?

George, there are a wide range of answers but what is the objective? What is the mission and environment and "customer" requirement??

If the engine cooling system (cowl inlet and exit) is designed for a lot of bypass air then what difference will one source of bypass make? As an experiment one could take off the muff and install a bypass valve. Vary the flow (bypass) and measure airspeed change (if that is what you are after) to quantify the change. But clearly there is more.

There are many conditions and results possible. Without an objective we don't know where we are going, what to quantify, and measure progress.

OK as a thought experiment lets say you want: good cooling under all conditions, but also want highest efficiency from cooling i.e. speed. Cabin heat is not an objective, but occupant comfort is desired.

So that can drive a cascade of design changes, inlet size, variable exit, eliminate all bypass and all heating hardware. Additional alternator amperage overhead. Now you can not have high speed efficiency w/o suffering low speed cooling, so here comes a variable exit, and (oops) we need those inlets larger. All this pressure for the exit will drive improved flow efficiency under the cowl. Balloon the cowl and radiant heat becomes more of a problem. Oops, there goes that oil temperature, larger cooler. See where this goes? You have a DanH (or ToolBuilder) system.

A single parameter improvements, even if they provide good benefit in theory, are frequently lost (or muted) in implementation without a corresponding change in the parallel system improvements that it enables.

Now the rest of the story. - High upper chamber pressure on my 7 drove installation of a bypass orifice to balance (reduce) airflow to the muff. My cabin heating is not adequate for temps below 8F without sunshine. It is due to tip up leakage pulling cold air from the aft fuse up my armpits. Another system issue not related to the question at hand. To help answer your question . . . I have high upper chamber pressure and wanted to know how the oil cooler flow affected CHT. The oil cooler shutter was completely closed and fully opened in cruise. I saw minimal change in CHT and no differential changes between cylinders, and no measurable speed change. The test point time was limited due to rising oil temps but it was long enough to detect the measure changes. Being a system thing, your results would likely vary and in a steep high power climb with marginal air flow across the heads it would definitely be a different story.
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Last edited by BillL : 05-24-2020 at 05:52 AM.
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  #19  
Old 05-24-2020, 06:05 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by gmcjetpilot View Post
YQuantifying "some" is the question.
So hook up a manometer and make two flights. The loss isn't huge, but it's there. Bobby Looper told us an ECI R&D project established a deltaP loss of about 1" H2O for each 1 sq in of leak area. I've not confirmed it myself, as I'm not cutting a 2" hole in a baffle wall for the experiment.

Quote:
Dan - from your +1 on Toobuilder's comment, I understand you have no heater? If yes, how do you stay warm in winter/altitude, same, heated clothing?
Aircraft was wired for heated clothing, and I put a hot vest on Ms Patti on really cold days. I wear a sweater and an insulated motorcycle riding suit over street clothes, as it's really comfy on a winter ramp. Good to zeroF OAT if the sun is out, maybe 15 OAT when overcast. Admittedly, where I live isn't very cold, 40 to 70 cruise OAT being the usual range, so the suit probably doesn't get used more than 5 flights a year.

I used the same suit to fly a Maxair in the winter, fully exposed to 60-100 mph blast. Electric vest went on at <45F. As Mike said, if your core is warm, hands and feet remain happy.

Quote:
Originally Posted by Toobuilder View Post
That significant amount of wasted CFM could be used to bring cooling under control OR reduce airframe drag (by reducing airflow through the cowl).
Yeah, and don't get me started on those silly blast tubes. Again, this is 2020. Let's install accessories with heat ratings at least up to SAE automotive standards.
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Last edited by DanH : 05-24-2020 at 06:08 AM.
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  #20  
Old 05-24-2020, 06:14 AM
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Jvon811 Jvon811 is offline
 
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My heat muff on my -4 also provides warm air for the carb heat.

I know, I know... Lycoming induction through the oil sump on carbed engines, etc... etc...

Those of you with carb's, removing the cabin heat, do you have two heat muff's? Are you going without Carb Heat at all?
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