Heater system on/off effect FE?

[UfoTofU]

This is actually a question from my brother, though I am curious myself.

I imagine that having the entire system on or off must effect your FE a bit but does anyone have a rough percentage?

I imagine that it is hard to quantify with there being so many variables (blower speed, outside temperature, etc.)

IT is an odd question from him seeing as he lives in California though.

[GasSavers_brick]

Thermodynamically, what really matters with regard to system on/off is how much heat is being drawn from the engine, i.e. how much heat is being blown into the cabin. If no heat is coming into the cabin then you are pretty much guaranteed that the heating system isn't having an impact on the engine.

As for a percentage, I think it depends on your driving cycle and how you use the heater. If you only allow it to run after the engine is fully warmed up then I doubt you could even measure the impact. An engine has to reject some heat in order to run, and all you are really doing is directing it into the cabin rather than through the radiator or out the exhaust. Trying to blast the heat while the engine is still cold is a different story, as it would prolong the distance over which the engine is burning extra fuel to bring itself up to temp. I imagine the penalty while operating in that state over a very short driving cycle could be quite steep since the engine management system will be fighting you every step of the way.

Of course, that's going to matter a whole lot less in Southern California than it does on a cold New England winter morning.

The short answer is "it depends." The only way to get a real answer would be through experimentation using the specific vehicle in question.

[rh77]

As we know, a warm engine produces the best FE. Unfortunately, it takes the 'Teg FOR-EV-ER (Sandlot movie reference) to warm up in cold weather. Long-story-short, I have to tough it out the best I can to get it to up to normal operating temp by not running the heater blower -- otherwise, you don't get the engine up to "waste-heat" temp and the TC comfortable to engage. On those cold nights in the 'teens when the car's sitting at the airport, it's a teeth-chattering "feats of strength" cometition to see how long I can tolerate zero-heat until the gauge is up to NT. When my fingers go numb is a usual indicator of when I need a little heat. But after about 20 minutes of driving, I get waste-heat and can get some warmth into the cabin; HOWEVER,

If I run the heater blower too fast, the temp gauge actually drops -- so it must be used in moderation. Honda built this cooling system to operate in the Mojave at WOT/full load all day long! This comes in handy in the summer when EOC'ing.

The solution? An EBH. I'm up to NT in 5 minutes, and can use the heat almost immediately. Only if they had plugs at the airport

RH77

[onegammyleg]

Originally Posted by theclencher

blasting it right off the bat will cause a delay in the engine reaching operating temperature- not huge but a delay nonetheless. .

Your rite.

For a little extra FE (especialy in winter) a person could experiment with using even more grill block (for better aero) and use the heater to provide the extra (and now needed engine) cooling.

But it would be a fine line between normal and overheating.

[onegammyleg]

Originally Posted by theclencher

but by how much I have not attempted to figure.

Blower motors are quite small. , usually in the 40 to 80 watt range., which would be equivalent to say 4 flasher globes.

Not much current draw there.

[onegammyleg]

Well , sure if Randy's fan is 189 watts that's 13 amps.

Thats quite some current , must blow a gale in there.

[psyshack]

I start getting the heater on as soon as it moves the temp gauge. Screw it. Im cold!!!!

Frost on the inside of the windows aint happening.

[landspeed]

Something to consider...

If a Blower is using 100 watts, and the alternator is only 50% efficient, then the Blower is really using 200 watts!.

If the ICE is only 25% efficient, then the blower is using 800 watts of raw petrol in order to generate 100 watts of electricity.

If you add up the wattages of all the bulbs in use at night, then double it, it can be a serious amount of power!. I'm looking into HIDs and LED bulbs for this.

[onegammyleg]

Originally Posted by psyshack

Frost on the inside of the windows aint happening.

Don't breath out , that stops window misting.

[Ted Hart]

Originally Posted by landspeed

If a Blower is using 100 watts, and the alternator is only 50% efficient, then the Blower is really using 200 watts!.

If the ICE is only 25% efficient, then the blower is using 800 watts of raw petrol in order to generate 100 watts of electricity.

Hmmm.... A blower motor uses 100 watts , period! Regardless of the wattage source (providing it is equal to or more than the blower motor). Watts = power-to-spin at some RPM. The RPMs won't go over the design value... but lower RPMs can be obtained fron a lower power source.
The (100W) blower will not "suck out" 100 watts of power if the power source ain't got it! Petrol, power company, or bicycle-powered generator! Watts cannot be made from the source! Regardless!
Regarding the power to spin the alternator...sure it takes more torque (and more throttle) to spin the loaded alternator (blower "on")...Energy out = energy in + losses.
Are we tangled up in our definitions? Hmmm....