Does heat use gas?

[s4rge]

I always thought heat used gas but i was wrong. =) Great news for the people who rather keep it off an dfreeze.

it is simply engine coolant diverted by a valve (actuated whenever you turn on your heater) into the heater core, which your blower simply pushes air across to bring heat into the passenger compartment. The coolant is pumped by the already-running water pump in your engine (you might lose an entirely negligible amount of power just from the added resistance of coolant going through the heater coil)

So, bascially all it does it use the heat already in the engine and transfers that to some part which opens up some blower things and toss the heat into your car Nice.

The A/c uses gas though if you wasnt sure of that.

[scionkid]

Strictly speaking, heater does slightly more gas. There's no free lunch in thermodynamics.

When you use heat, the heater core and the radiator both take heat from the coolant, not just the radiator. When the relatively cooler coolant flows back into the engine, there's a slightly larger temperature difference between combustion gas and coolant. Hence, more heat transfer and slightly less pressure rise in the cylinder, which requires a slightly larger throttle opening.

[littleredcar]

Interesting, sounds true. However, it still doesnt use more than the a/c does? And scion kid, are you an automotive engineer?

[Krakilin]

Plus the fact that you need electricity from the blowing fan, which means a bit more gas (very very slightly though)... but for sure, it doesn't compare to A/C, A/C uses your engine, it actually lowers the power of your car.

[starshifter]

I kind of doubt what Scionkid says. I never studied exactly how the heater works but I think cold air always takes heat from the coolant. When the heat funct ion is off, the now warmer air flows outside of the cockpit. With the heat function on, this air is now blown into the cockpit at the expense of an electric fan powered by the battery which is always being recharged as long as the engine is running. And even if I'm wrong, I doubt one could really measure a difference in fuel consumption with and without heater.

[scionkid]

Check this out in howstuffworks.com

When you turn on the heater, you route some coolant to the heater core. This takes heat away from the engine, creating a greater temperature difference on both sides of the cylinder wall. This temperature difference causes more heat transfer away from cylinders. I know the difference in fuel consumption is essentially nil but the original post claims no fuel efficiency lost. BTW, any electrical accessories inside the car is powered solely by the alternator. cartalk.com says you can disconnect the battery from the car and it should keep running, at least those w/o computers.

Now, if the system works as starshifter described, there would be no extra fuel consumption. And no, I ain't an automotive engineer, but I do have a degree in mechanical engineering.

[IMBoring25]

If the coolant was cooler, seems to me you could close the thermostat a bit, reducing the work required to pump coolant, and cutting losses to the cooling system? Makes sense to me, and that would seem to imply an almost-imperceptible INCREASE in fuel economy. I could be way off base, though.

[scionkid]

Hmm, never thought about the thermostat. If I'm to design the cooling system, I wouldn't put in a thermostat that closes because of a small drop in coolant temperature. Having the thermostat open and close like that increases wear of the thermostat and is simply asking for trouble. Then again, IMBoring may be right.

[IMBoring25]

Whether the thermostat has an infinitely-variable opening or digital control, the end result will still be less coolant flow over a period of time. If the opening is variable, it will close a little. If the thermostat is digital, it will spend a minutely longer portion of the time closed in each open/closed cycle. Over time, the result is similar. I suspect the reality is somewhere between the two extremes; Highly variable, with a bit of deliberate hysteresis.

[starshifter]

Check this out in howstuffworks.com

Thanks, now I understand your argument.

[Tiamat]

cartalk.com says you can disconnect the battery from the car and it should keep running, at least those w/o computers.

Not true! Unless my thermo class was way off base (I'm an ME, too) the cycle isn't self sustaining. Without the battery to drive the spark plugs, the car dies. Actually, I know this from experience as we had the connecters come loose once and the car did indeed die. Now, in a diesel, you're set once the thing is running since combustion is spontaineous due to compression.

Also, when you do the math on engine efficiency, you neglect heat transfer entirely because you assume that things take place so fast that it doesn't matter. Obviously, heat transfer does happen, so this may have been a simplification for the sake of the students. That aside, if you have a cooler engine, you may have a more efficient engine. The lower the intake temperature, the better compression ratio you have and thus the more efficient the car. (I'm assuming that a lower engine temp would help with the intake temp, by the way, but I don't actually know that it does. Sadly, I have little practical experience with cars.)[/quote]

[scionkid]

http://standardshift.com/forum/viewtopi ... 4&start=30

Alternator should power the spark. Have you notice your rev drops then comes back to idle when you turn on the headlights or turn on the defroster wires? That's electrical stuff drawing from the alternator (not the battery) and the engine computer brings the idle back to where it used to be.

And I did address heat transfer. Use the heater, and it takes away heat from the coolant. The coolant would be cooler than if no heater was used. When the combustion occur, there would be a greater temperature gradient between the flame and the coolant (since the coolant is now cooler by maybe 10 deg F, I don't know the exact number). But this coolant is still near the engine's operating temperature and the intake is a lot colder than that.

[TransAm350fi]

Heaters do not use gas. The source of the heat when you turn your heat on is the hot air that is in the engine bay. When your heat is off, that heat is kept inside the engine bay, when its on its let out. This is why people say whenever your car starts to overheat, turn on your heat and roll your windows down (or leave em up if you dont mind the heat).

[Krakilin]

Heaters do not use gas. The source of the heat when you turn your heat on is the hot air that is in the engine bay. When your heat is off, that heat is kept inside the engine bay, when its on its let out. This is why people say whenever your car starts to overheat, turn on your heat and roll your windows down (or leave em up if you dont mind the heat).

Dude, did you read the above posts?

[acadien]

suggestion:

• 1.don't bring back dead posts
  2.dont bring back dead posts by repeating what was already said