[oil pan 4]

Originally Posted by renault_megane_dci

I have to admit I am interested in using exhaust heat.

So how would you guys do it ?
I think copper tube rounded around exhaust tube and held in place with some exhaust insulating wrap.
Then use thermosiphon principle : heat goes up and does the flow in the system.

http://ecomodder.com/forum/showthrea...ler-29085.html

Originally Posted by blownoiler

Exhaust temps would most likely climb too high for this type of system, boiling the water to steam, I foresee extremely high pressure in the coolant side of the exchanger. You would need a way to stop the exhaust adding heat once the engine was warmed up, otherwise a cooked engine is on the cards. Something similar to an egr valve is what I was thinking, which would enable you to switch the exhaust heat off when not needed.

Don't use an EGR valve, they only flow a tiny volume of exhaust.
If you are going to do this, go big, use all or most of your vehicles exhaust to heat coolant.
Use an EGR cooler like in my above post and an exhaust butter fly valve. I have several exhaust valves in my junk collection every thing from 100% cast iron GM 1980s junk to very high end fully CNC machined stainless steel exhaust butter fly valves used on motor cycles that are only a few years old.

Originally Posted by renault_megane_dci

IIRC BWM added some kind of steam engine on their transmission shaft not so long ago to use that exhaust heat.

Will try and gather info on this.

Classical boiler design tells us we need about 10 to 12 square feet of boiler surface area for each Horsepower we want to produce. Classic boiler design assumes a differential temperature much higher than what you will get in a vehicle exhaust. So the heat exchanger surface area per Hp gets even bigger. A lot bigger.

It could work if you are a mechanical engineer who used to build boilers. Most of us are better off just repurposing a big diesel EGR cooler and exhaust butterfly valve for use on a car to create unbelievably fast warm ups in cold weather.
Then pipe the heated coolant to which ever system you would like to heat.

Originally Posted by rh0

I'll also recommend Evans coolant, especially if you plan on exposing your coolant to exhaust temperatures.

Just about every single diesel engine made since YM2007.5 has coolant and exhaust interfacing in a heat exchanger and the factory fill coolant isn't the problem.