Warming the coolant with exhaust?

[oil pan 4]

I don't think that a normal car egr valve would flow enough to make a difference. I think it would have to be a big EGR like for a diesel or something.

[EcoCivic]

Originally Posted by MightyMirage

If the thermostat shuts coolant flow thru the engine off until it's hot, how do you gain efficiency? Asking for a friend...

I do like the EGR valve idea, maybe you could copy DOAX idea and heat the oil pan and trans ?

You gain efficiency because you are still circulating coolant through the engine with the thermostat closed, just not through the radiator. Coolant is always flowing through the engine, weather the thermostat is open or closed. This is why you can get heat before the thermostat opens. Does this answer your question?

[cRiPpLe_rOoStEr]

So, what are you most inclined to do? Is a custom exhaust header totally out of question? And what are the gains you're looking to get from this heat exchanging? Do you think it would also improve emissions?

Originally Posted by EcoCivic

You gain efficiency because you are still circulating coolant through the engine with the thermostat closed, just not through the radiator.

Even with most of the coolant flow not going through the radiator while the thermostatic valve is closed, at least a small amount will always circulate through the radiator, otherwise there would be a vacuum buildup inside the radiator tubes which would shut them.