Mufflers and which heater box?

[Pilottonny]

Hello fellow builders,

I am at the point of ordering my FWF-kit. Also I am in touch with Larry Vetterman about the supply of an exhaust system with mufflers (noise restrictions in Europe!). From Larry I learned that the mufflers have to be air cooled. The hot air from one of the mufflers is also used for cabin heat.

I have already ordered the cold/hot heater valve from Vans, instead of the standard heat-box, because I like the additional comfort during the hotter season, being able to have a cold air flow underneath the instrument panel, to keep the feet/legs cool(er).

Since the mufflers need a constant flow of air, they should not be shut off (as you would with the hot/cold heater valve, when switching to cold air, or when closing the valve completely).

Larry tells me to use the ?Standard? heat box, but this will let the hot air flow into the engine compartment, when cabin heat is not required and unnecissarily heat up the firewall (certainly arround the heater box area). Apparently the air from the mufflers is really hot! Obviously with the standard heater valve the cold air is not available either, which makes the "hot" situation worse.

How have others done this? Or has anybody seen an installation like this?

Regards, Tonny.

[drill_and_buck]

Hi Tonny:

I am building an RV-8 and have installed a Vetterman exhaust with dual mufflers. For installation I purchased 2 standard heat boxes. Each muffler attaches to a separate heat box. I have one heaterbox directed to the lower area and one connected to an eyeball vent in the cabin that can easily be directed. When heat in the cabin is not needed the heaterboxes vents are closed and hot air is dumped overboard. Hot air will not enter the cabin.

Each heater box valve can be opened or closed via a push/pull cable.

I have not heard of the heater box area heating up. However, I do plan to install some firewall insulation on the cabin side.

For cool air to the cabin I have two eyeball vents on the panel.

Hope this helps. Good luck with your project.

Mike Draper
RV-8 Finish
N468RV

[Shockwave]

I'm curious about mufflers as well. How well do they work? How about a muffler from Midas, or would that not work for some reason(s)?

[Pilottonny]

I opted for the Vetterman mufflers, because they will fit without any modification and also give good heat. The only alternatives I could find anyway, are the "Swiss"-muffler, a huge pipe under the belly and the "Liese" mufflers, which are very expensive. They look kind of cool though, just stiking out approx. 8" underneath the cowling.

Larry said the noise reduction is 6dB? I got no idea how much that is in real-life-earbaching units.

I hope it will suffice the European regulations, when the tests are done for the noice certificate.

Regards, Tonny.

[jdeas]

6db would be perceived as 1/2 the level