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bluemaule

Member
My RV-7 heater doesn't put out much heat. I've been told that stretching a screen door spring out and wrapping it around the exhaust pipe inside the muff slows the air down and greatly increases the temp of heat coming into the cockpit. Anyone know if that works? Any downside/danger? Thanks for your help!
 
I found on mine, if I throttle open the heater valve instead of full open, I get a better quality heat. Lower air flow, but higher temp. Yeah, I know, it makes no sense: What is not going to the cabin is getting dumped to the cowling via the heater valve, but it is what it is. I have flown with only a light jacket with it being in the low 20s outside. I did install heated seats. The wife is the only one to have ever turned them on. of course, if it is 50 degrees outside, she is freezing (That is why I put them in).
 
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Heat

I added another heat muff on the other exhaust on my 6 and ran together in series. Got more heat then I need. Doing the same thing on the 7 I'm building.

Mark
Fairmont , MN
 
Add another heat valve and muff ...

Some builders have added another heat muff and valve; installed it on the pilot's side, and then directed the center heat distributor toward the passenger side.
 
I have 2 Robbins heat muffs on a Vetterman crossover system, each running to an "RV-4" wedge shaped valve on the firewall. One for each seat. When I bought the muffs there were some complaints as to their performance and Jeff told me to block off some of the inflow from the 2" scat. I only have a 1" hole for the input air and they provide more than enough heat, even at 0 F.
 
Heated seats

I put in 2 heated seats. That plus normal heat muff makes us nice and warm at any altitude. I think it cost me around 100 bucks on ebay for a 2 seat car kit. Just throwing out another option.

Christopher.
 
Muff Springs

I used heavy springs inside the carb heat muff for my Long-EZ, it definately helped, but after several years the exhaust pipe heat takes a toll and eventually some of the loops broke.

What Al says does make sense, the lower flow rate through the muff allows more time inside the muff to pick up heat, thus the temp will be higher. Q=mV DeltaT. Volume goes down, Delta T goes up.

I've flown my -9A with temps in the 20's and have adequate cabin heat with standard installation. It's not in the 70's, but does a good job taking the "nip" out of the air. Guess it all depends on what your expectations are. After flying the Long-EZ 22 yrs with no cabin heat, the RV heater is awesome!!
 
Here in East Tn, I have found that if I don't have enough heat, all I need to do is lean properly and it comes right up to snuff....
 
I have Larry Vetterman's muffler system- which only fit engines with vertical draft sumps at this time- on my -7. Using only the can around the passenger side muffler, plumbed to a firewall mounted valve per plans, I get enough heat to drive us out of the cockpit even at 15? F OAT.

She Who Has No Body Fat (my wife, bless her heart she's better at keeping the weight off than I am) is always cold, but can't stand having the heater knob pulled all the way open. Too hot.

Just another option...
 
I make up stainless coils out of SS welding wire (MIG / TIG?), wind it up on a 1/4" rod & wrap the exh pipe inside the heat muff (wrapped tight enough so won't wear out enything), not too dense, as we in Canada need both heat & lots of volume. I found the pot scrubbers too restrictive.
 
Just keep in mind that the heat muff should come off at your CI and the exhaust pipe examined for any possible holes or errosions. If you do wrap it with something, you will have to remove it to inspect.

Anytime you wrap the exhaust or restrict the airflow the exhaust pipe temps naturally go up in that area. It may or may not cause a problem as there are no joints or welds to break there but I had to trash the exhaust on my Bucker due to excess heat and carbon imbrittlement making the crack in it unrepairable. In fairness, my exhaust was wrapped all the way inside the cowling. It is no longer wrapped and the heat is dealt with cowl shields now.

Not saying don't, but there is rarely a free lunch.....
 
+1 on the heat muff with mufflers. I too have one heat muff around one of the mufflers on my RV9A and at the most I pull the knob out about a quarter of an inch and get lots of heat. Pull it out all the way and you'll think your on fire:D
 
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