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New style heat box and carb ice

P

Peter1

I'm New Here
I would like to share my concern with the carb heat system on my RV7. After twice experiencing carb ice immediately after take off I think the new style muff provides inadequate heat on the ground. After taking off the scat to cabin heat and blocking the outlet on the muff I get 70rpm rev drop and with the cabin heat pipe installed only 15 to 20 rpm drop. As the end of the cabin heat pipe remains open it may be an easier path for the engine to suck air rather than around the tight baffles inside the heat muff.
I would like to hear from anyone with experience with the new muff.
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Pete. I've never seen that large carb heat muff before. Way more robust than what I have.

Also notice your intersection fairing on backwards, looks likes it's photobombing.
 
Very nicely made Bugsy but not sure of its effectiveness for carb heat in run up mode.
Slipped the fairing down there to take the bottom cowl off.
 
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Pete. I don't see any appreciable rpm drop with carb heat. I have seem minor icing induced stumble in high humidity which was corrected with cab heat so assume I'm adequately protected. My carb heat muff is way less robust than yours, it's not the vans system, better than that, I forgot where I bought it from.
 
What Carb have got ? Have you sorted out the problem ? I am in the process of installing the same cross over system with the same heat muff ! any advice ?
Thanks .
 
See notification 14-10-24 on Van's website. Also, do a search on same for drawing OP-54, it is updated as per the notification.
My aircraft is not flying yet so I cannot report on performance of carb heat.
Vic
 
One tirck pony

One trick I have heard of is to wrap a stainless steal spring around the pipe under the heat muff shroud,to increase the area of airflow contact.
 
Carb heat

Hi Pete,
I'm glad to see your question. I have the same heat muff on my O360. Likewise, I get very little rpm drop when applying carb heat. I am contemplating tightening the gap of the carb heat flap in the intake inlet for starters. The side ports where the carb heat scat tube clamps to the top of the air box is suppose to let the air in there for positive airflow so i dont think it is backflowing up the heat tube. Another thought I've had is adding a very small deflector at the air inlet tube to the heat muff itself, at the left engine nossel, making a mini Ram air deflector behind the screen. What is your thought on that?
Mike
 
if you have not already done this...

When I did my carb heat system I used a Robbin's Wings muff and blocked off the side inlets at the air box. Seems to give adequate carb heat and air flow, but then it's only carb heat... I have mufflers for cabin heat... I'm running an O-375.. Upon pulling carb heat during runup I get about 70 rpm drop and can see an immediate increasing trend with carb temperature although I have not waited for it to stabilize to see how much.

Note that some have expressed concern whether the 2" scat will carry enough intake air for the engine, but at least with mine I have not noticed a significant power reduction in flight with full carb heat.





 
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New style heat muff

Hi Mike and Ron
I just blocked the cab heat outlet on the heatmuff and fitted a second heatmuff for cab heat on one of the side pipes.Have a rev drop of 70-80 revs now so am a bit more confident it's working. The rev drop before was only around 15revs which suggests it is getting adequate air through the scat but it just wasn't warm enough?
Carb is a MS4-5
Pete
 
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