Using hot engine/exhaust air for heat?

[42Bfast]

For the Roadster builders that chose the glovebox instead of the heater,.....

Has anyone considered, or even better, developed, a method to capture or allow hot air from the engine compartment to enter the cockpit in the winter for heat?

We spend a great deal of money and effort in insulation etc, to keep the heat OUT. Shouldn’t it be possible to strategically place some controlled “vents” to allow some of that heat in, when it’s cold outside?

The transmission tunnel or the foot box (mere inches from some very hot headers) seem like likely candidates. Would some collector shrouding be necessary?

I’m still very early along on my build having stopped to do a major renovation on the house. Yeah, I know, somehow I got my priorities warped up and decided to finish the house first.
Messed up priorities notwithstanding, I haven’t seen this discussed in the forum at all so I’m tossing it into the ring for discussion.

After all, our cold feet are just on the other side of some pretty thin aluminum to the exhaust system. How to keep heat out when we want it out, but let it in when we want it in, is the question.

This is hardly an original idea. Growing up on a farm in Tennessee, it was fairly common in the days before cabs on tractors, to see self fabricated sheet metal, canvas, or even burlap “shrouds” along the side of the engine cowlings to direct the heat back to the operator.
And of course, the air cooled VW’s captured engine heat for the cabin.

Would it be as simple as say some waste gate style vents in the foot box and along the transmission tunnel?

Any ideas out there?

[Just puttering]

I was thinking people put pool noodles in to seal in front of the doors , pull them out during the winter. Although some of us have cool mornings then hot afternoons ......

[Olli]

Just get some seat heaters they will take the edge off on cold mornings.

Olli

[wareaglescott]

My 79 911 has this sort of set up. Just a metal box around the headers that collects the air, a blower fan and some ducting that brings it to the cabin. Works great.

[Boydster]

Small piston aircraft have used the type of heater that Scott mentions for many, many years. Only moving part is a push/pull cable.

[Cobradavid]

My 79 911 has this sort of set up. Just a metal box around the headers that collects the air, a blower fan and some ducting that brings it to the cabin. Works great.


Didn't the old VW Beetle use a similar concept?

[UnhipPopano]

I remember the VW system used for the Bug, but I remember that it did not work very well. An Ice Scrapper was mandatory for clearing the ice off of the windshield!

[NAZ]

There is certainly enough heat energy in the exhaust but it is difficult to capture a large percentage of it. Fortunately, there is lot's of it so capture efficiency should not be an issue. You can expect to generate ~2,544 BTU/hr for each HP you produce. Roughly 50% of that heat will be dissipated through the exhaust and ~30% is handled by the cooling system. So take your pick, either has been used successfully and is rather easy to design a system that will transfer some of that heat into the cockpit. Both have their pros and cons and the application will dictate which is the preferred method. However, with exhaust heat you must be careful that absolutely no exhaust gasses are allowed to enter the cockpit through the heating system. As mentioned above, piston aircraft have been using an exhaust waste heat capture system to heat the cabin for many years. One of the routine inspections piston aircraft are required to pass is to pressure test the exhaust heat capture system to ensure no exhaust leaks will migrate into the hot air supply to the cabin. Perhaps not such a serious problem in an open cockpit like a roadster but still something of a safety issue you must consider.

[Papa]

Didn't the old VW Beetle use a similar concept?

Yes, my 1965 VW bug had ducting to route engine heat into the car, but no blower. It was okay at warming the interior of the car, but not so good at defrosting an iced up or even fogged up windshield.

[Avalanche325]

You can, with a little effort, put the heater in the middle of the fire wall, at least with an SBF. I have a heater and a full size glove box. You do have to do some basic fabrication. HF metal brake is all you need.

It would be a lot more effort to do VW style heater boxes. As mentioned, they didn't work very well.


Here is a shot of mine.
115583

[Duke]

Yes, it's possible and works rather well. See my build thread.

I ran fan motors to fresh air vents in the foot boxes, but since I used the front vents for brake ducts I just terminated the fan motors on the firewall near the headers. Turns out it became a de-facto heater by accident. That and the heated seats work great in the NE cold weather.

[BLUE KNIGHT]

Hi, I haven't posted on this site or the previous one in years. I'm returning to the whole " Cobra " thing. I have FFR 2972K. Yep it's been around awhile just like me ( I'm 72 :D ) ….. I live in Vermont ( Sugarbush Valley about two thirds up from Mass. border ) …. so it gets cool late Sept. thru Oct. … I discovered that if I removed my cover from the top of the pedal box a lot of heat would just blow in from headers & motor ( I would definitely leave this closed during the summer )( I have an EFI 5.0 engine ) … I don't get any smell/odor from this, so I guess the exhaust system is pretty well sealed …. anyway, to your issue, I also have a BRP, Can-Am Spyder ( touring model ) … When they were using a V-twin for the engine there were some heat issues which affected the engine and rider ….. I found that using " small 12v computer fans " … if strategically placed - could move a lot of air either in or out from a confined space. They are thin, come in various sizes from 40mm dia. to 90mm … they use almost no power & are very quite. My thoughts were to mount one high on the right side of the driver footbox, activated by a switch, with a simple sliding door ….. I bought mine on E-bay for less than $ 5.00... just a thought from me ….. a sort of newbie …. Mike :cool: