[Blizzard]

Just brain storming (small storm for me). Surely I'm not the first person to think about this but I've never seen anyone mention it. The 10 creates so much excess heat to the cabin and blasts the heater valves with hot air. Some have speculated that this may be a contributing factor in the hot tunnel issue. I haven't done this because I'm not yet flying, but what if you used only one heat muff to heat the cabin. You would have to choose which heat you wanted ie. front or passenger. By choosing one or the other you could use the other heater valve to vent cool air into the tunnel by routing one of the scat ducts directly to the heater valve and bypass one of the heat muffs. You would need to cap the intake and exhaust ports on the heat muff not used. Is this viable or is there a problem with this set up? I'm also wondering if you could meter the scat duct air coming from the baffles to the muff you decide to use to reduce the volume of air to it. I replaced by aluminum heater valves with stainless. Now I have an extra valve I could use between the baffle scat and the muff inlet. Again...just brainstorming. I can always count on the forum for "Hey! That's a good idea" or "Dude ! Are you crazy? That's a horrible idea!" Thanks

 

[Jesse23]

I live/fly in Florida. Stock under the cowl . I have no heat (excess) issues in the tunnel. No elaborate matting, extra FF covering, etc. Disconnect one of the muffs, if you have a tunnel ‘Hot’ to the touch.

I climb out at 120 KIAS. (Full throttle/2450). May bring MP back to 26, if I approach 380/385° CHT.

 

[rocketman1988]

I have the Custom Aircraft exhaust in a showplanes cowl. I have had ZERO issue with hot tunnel; in never even gets warm.

When I built the aircraft, I actually installed a dump valve "Y" in each SCAT tube. The valves are controlled via cable from the cockpit. The idea was to dump the hot air from the heat muffs in the cowl exit flow so as to keep the hot air away from the firewall and heat valves.

I have never needed to use them, and in fact, will likely remove them at the next condition inspection.

I have no insulation on the firewall or in the tunnel.

 

[Blizzard]

That's all good to know. Like I said,I'm still building, so a lot of what I brought up is "what if". Was just curious if anyone had done what I proposed. I'm going to finish as per the plans and I haven't added any heat shield or other things firewall forward either. I actually haven't seen much lately about hot tunnels so hopefully that has been resolved. Thanks so much for the input.

 

[dres0044]

I have the Custom Aircraft exhaust in a showplanes cowl. I have had ZERO issue with hot tunnel; in never even gets warm.

When I built the aircraft, I actually installed a dump valve "Y" in each SCAT tube. The valves are controlled via cable from the cockpit. The idea was to dump the hot air from the heat muffs in the cowl exit flow so as to keep the hot air away from the firewall and heat valves.

I have never needed to use them, and in fact, will likely remove them at the next condition inspection.

I have no insulation on the firewall or in the tunnel.

Rocketman
What “y” tube setup do you use?

I have the hot tunnel issue. I have installed insulation on the inside of the tunnel (and it helped a lot), but I have no fabric or anything on the outside of the tunnel. (No fabric covering) so my leg rests on the bare aluminum tunnel. I think a lot of people have insulated fabric covering and just masks the heat issue (just my opinion)

I think having the y tube diverted isn’t a bad thing. The inside of the tunnel I bet still gets hot.

If you take yours off, I would interested you in your setup.

Thanks
Jeremy

 

[syfhmasta]

Rocketman
What “y” tube setup do you use?

I have the hot tunnel issue. I have installed insulation on the inside of the tunnel (and it helped a lot), but I have no fabric or anything on the outside of the tunnel. (No fabric covering) so my leg rests on the bare aluminum tunnel. I think a lot of people have insulated fabric covering and just masks the heat issue (just my opinion)

I think having the y tube diverted isn’t a bad thing. The inside of the tunnel I bet still gets hot.

If you take yours off, I would interested you in your setup.

Thanks
Jeremy

Jeremy,

Pic below of the wye I used from ACS. The solenoid was ordered off Amazon and I built the adapter.

This wasn't done because of hot tunnel, I had no issues before, but it had a little warmth. Absolutely zero tunnel heat now.

I did it because the hot air would dump into each other mid firewall, and because I have a plenum and no leaks, there didn't seem to be any air flow to pull all that hot air out of the upper firewall area, which was burning out my main alternator fuse which is mounted copilot side of the firewall at around the same level as the heater valves. I ended up installing a temperature probe in the area and was seeing temps in that area above 200 degrees. After installing the wyes and diverting them down towards the cowl exit, the area in question temperature lowered significantly, roughly coincident with block temp (oil temp minus a little).

The scat tube coming off the wyes is rtvd into the triangle of the front gear pointing exactly at cowl exit. So when the cowl flaps are closed, there isn't a ton of cooling exit area. Even summer through Texas cruise temps were around 350, so still plenty of cooling flow.

I should mention, when the wye is open to provide heat, the flow is slightly reduced from prior to this mod. Still plenty of heat IMO, and I hardly use the heat, but if your mission is way up north in the winter, this might not be the mod for you. The wye either dumps everything, or splits the flow, it doesn't do one or the other.

Hope that helps.

Roy