[Eddie]

Hi all

My firewall gets very hot and I know that the cabin heat system is the culprit. I live in sunny South Africa, but my RV6 was built in Vancouver. It has 2 heat muffs that feed from the rear baffles on either side, through the muffs and then blows it against the firewall on both sides, which creates all the heat on the firewall. (picture attached) I am yet to be cold in the RV, but I have had many sweaty rides in summer.
My plan is to remove the entire system and close off the holes at the back of the baffles and put some heat protection on the cowl where the heat muffs where.

Any tips or warnings when doing this?

 

[curtis]

Two things I do during the summer;
1 - Remove the heat muff assembly from exhaust
2 - I attach the fresh air scat hose from the baffle directly to the firewall connection. This is another source of ambient air in the summer.

 

[pierre smith]

Hi Eddie...be sure and block the firewall holes with stainless (obviously).

Best,

 

[rmartingt]

It has 2 heat muffs that feed from the rear baffles on either side, through the muffs and then blows it against the firewall on both sides, which creates all the heat on the firewall.

Wait a minute... are you saying that the air from the heat muffs doesn't go into the cabin, it just blows against the firewall and exhausts into the cowling enclosure, and does not go into the cabin? That seems like an awful strange way to do cabin heat, but that's what it looks like from the picture.

If that really is the case, I see no harm in doing exactly what you propose.

 

[F1R]

Post #2 is what I do. Remove the heat muff from the exhaust for the summer but I link the air from the baffle port direct to the firewall to feed fresh air to the cockpit. In the fall , I put the muffs back on and re plumb through the muffs.

Since you have a carb, not Fuel injection, there is no safety issue getting ventilation air where it now comes from and I would be inclined to keep using your baffle feed ports for CABIN ventilation.

If you have other cold air only vents for the cockpit, then you could close off the baffle ports.

It is important to actually take the muffs off the exhaust pipes if you do not have air moving through them for the summer.

 

[rzbill]

Like Curtis said:

Remove the muffs from the exhaust pipes. Without the air going through the muffs, the exhaust pipes get hotter than normal, shortening the exhaust pipe life. Removing the muff solves this.

Block the hole in the engine baffles.

Your choice on whether to do anything with the valve on the firewall. If there is chance of future sale, you might choose to leave that valve as it is.

Secondarily, I find you comment about the firewall getting hot unusual. I have dual muffs on my craft (as does another RV near me that I fly with sometimes). In neither craft is any unwanted heat noticed while the heater valve is shut. Are you positive that your heater valve is closing properly??

 

[DanH]

Is that a sheet of Dynaliner closed cell rubber sheet insulation on the firewall?

 

[Eddie]

Wow... the power of VAF, Thanks guys

The previous owner closed the valves properly with another piece of stainless and screws. (1st sign of hot cabin) So I cant use it anyway...

I will close off the baffle holes with stainless plates, maybe make a couple of small holes to ensure ventilation between firewall and engine?

Yes Dan, that is 1/4" Dynaliner on the firewall, you ask as if it might cause a problem there... It is almost impossible to get to the firewall on the inside on a flying plane. So after they told me its safe and fireproof, I put it on the easier side of the firewall. It does make a difference in heat and noise, but I know the hot air is still being pumped onto it.

 

[jaradtke]

The valve is mounted upside down. The source air is blowing directed up the firewall, when the valve is closed, instead of down and out the bottom on the cowling.

 

[Beancounter]

firewall insulation

Eddie
Your part of a community here and we try to look out for each other. Dan questioned the use of the rubber on the firewall because it will burn and smoke vigorously in the event of an engine compartment fire. That toxic smoke will find its way into the cabin. Please consider using ceramic fiber blanket. Common practice is to apply it to the hotside of the firewall covered with thin stainless sheet. This product has superior insulation qualities to rubber.