carb heat question

drn1021 · #1 02-20-2007, 01:15 AM

I am a fairly new owner of RV-9A. The engine is an 0-320E2D.
The builder apparently elected not to hook up a hose from the top of the filter housing to the exhaust, so when you engage the carb heat all it really does is block the filter inlet where outside air comes in and opens a door to the inside of the cowling. When carb heat is applied the carb temp gage shows only a small increase in temp.

Is this commonly done, or is this something you would change immediately before flying very much?

I've flown 182 with 0-470 and icing was problem, but I've had a couple people tell me icing is not as big a problem with this engine.

Thanks,

Donny Niebrugge

Ironflight · #2 02-20-2007, 04:35 AM

Donny,

What you have is the standard Van's carb heat - the builder assembled it exactly per plans! Now, the question about how much good it does as carb heat should spark a healthy debate.....frankly, I'm surprised that you see any measurable temperature rise at all.

Many folks (myself included) add a heat muff on the cross-over exhaust with SCAT tube down to the heat door, but I have doubts if it makes things much better. Living in Teas, carb heat rarely comes up as a topic of discussion in pilot's lounges, so I guess the concern has slipped into the back of my mind, but I have rarely experienced it with Lycomings.

Now I'll let some actual experts chime in!

Paul

terrykohler · #3 02-20-2007, 04:59 AM

Lycoming powered RVs are not as prone to carb ice as continental powered Cessnas due to carb location. On the other hand, if you plan on flying in Northern climates, at higher altitudes (think lapse rate), or IFR, then carb heat is something you should have available, if nothing more than for peace of mind. Sounds like everything is already in place in your AC. As Paul mentioned, looks like you only need a cross over heat muff, some scat tube, and a couple of hose clamps. Twenty minute job. Cheap insurance. Just a couple of ounces. Agree that the Van's setup doesn't provide substantial heat-think of it as anti-ice rather than de-ice .

Mel · #4 02-20-2007, 07:27 AM

I flew my -6 for several years with the original carb heat as you describe and never had a problem. As has been said before the Lycoming is not as prone to carb ice as the Continental. Having said that, I have since added a full muff just for "piece of mind."

drn1021 · #5 02-20-2007, 08:18 AM

Thanks for the quick replies. I think I do want the added comfort from a little better design than the original.

I found a few pictures showing a heat muff and scat tube to the inlet but they dont have an air source. Don't you need to run some scat tube up to the baffle area of the engine? If anyone has some pics of their setup, I would appreciate it.

Donny

az_gila · #6 02-20-2007, 08:22 AM

I think this is the one you need.... no air inlet hose needed...

http://www.robbinswings.com/Carb_Heat_Muff.htm

gil in Tucson

rv9av8tr · #7 02-20-2007, 08:44 AM

I've flown a Lyc 0-320 on my Long-EZ and experienced carb ice twice.... both times requiring an immediate landing as it would not clear. I was lucky to see a 10 deg temp shift with carb heat. I solved the problem by making a muff similiar to the picture above and maximized the heat transfer surface area inside the muff by attaching "large" dia. springs around the pipe, between the pipe and the shell. After that, air inlet temp to carb raised 40 deg with application of carb heat.

Mike Rhodes
RV-9A fuselage
LEZ N234BM flying

drn1021 · #8 02-20-2007, 10:01 AM

Just what I needed!! Thanks guys