Vanilla55

I'm sorry for the technical and pretty lame question, but I've been pretty curious about this.

Heated air (for the passenger compartment) in older cars seemed to get some of its warmth from excess engine heat. I think this is why it was always said that if you engine was overheating in an older car, you should turn your heater on full blast at the highest temperature.

My Lexus service guy said this wouldn't work in my IS 250. I took this to mean that the heater in the IS 250 acted independently from any excess engine heat.

You see, since too much heat isn't a great thing for an engine, I used to drive my old car with the heater off but SET to the highest temperature. This way, I would NOT be using the fan, but I would still draw off some excess heat from the engine. (I could be wrong, but this was my thinking.)

Well, is it true that I can't do this for my IS 250? I know it probably doesn't make much of a difference, but I am just really curious about this.

The main reason that I want to know is, if the heated air in the IS 250's passenger compartment comes solely from an electric heater that draws power off the engine, I'll try to keep my cabin temperature low to minimize power usage.

However if the heater takes advantage of excess engine heat to warm the air headed toward the cabin compartment, then I'll set the temperature high and enjoy my winter driving while being nice and toasty.

Does anyone know which case it is?

Bichon

There is no electric heater in the car. Heat is provided by engine coolant flowing through the heater core. Feel free to set the temperature as high as you like.

Coconut

So, in other words turning on the heating doesn't rob power like the AC does??

n8236

But doesn't the engine provide the power to heat the coolant flowing thru the car? And thus, robbing engine power?

Byprodrive

iTrader: (1)

The coolant is heated as a result of the engine running, when you turn on the heat the coolant is routed thru the heater core (a small radiator) and the blower fan blows air across the heater core to the vents. this cooling effect can increase engine power slightly although modern engines run at a much more constant temperature than older engines (80's & older)

Bichon

That's correct.

Internal combustion engines are far from 100% efficient. Only a portion of the energy produced is used to move the pistons, the rest is waste heat that would quickly destroy the engine if it weren't removed. Turn down the heat and the energy you save won't be used to power the vehicle, it will simply be transferred to the outside air flowing through the radiator.