Simple and cheap DIY exhaust heat to coolant heater idea - using air to transfer heat

[Piwoslaw]

Originally Posted by Daox

Daox, in the diagram above your fan is sucking in cold, outside air, which then wastes all heat which is not absorbed by the coolant by dumping it into the atmosphere.

Looping it back to the intake would help you recycle this waste heat, getting hotter air, so increasing heat transfer to the coolant.

If the air in the closed loop should not be heated once the coolant is hot, a simple trap door could open to vent the loop. This door could either have a (normally open) closing mechanism wired to the fan, or be closed by the pressure the fan generates.

[Daox]

I completely agree that a closed loop would increase efficiency. However, I would imagine most fans out there aren't designed to handle a massive amount of heat. Ideally, you would want to pull a LOT of heat off the exhaust, so it may become an issue. If you did close the loop, you would just need to be careful about how hot the air actually gets, and make sure your fan can handle the heat.

[rmay635703]

The 2016+ Malibu Hybrid has a exhaust to coolant transfer device from the factory,

Should find out how much the off the shelf part costs and how it operates,
Sometimes you luck out and it’s not bad