This Hybrid has two radiators, and two closed coolent loops, and each is on the small side. ( one for engine, one for electronics ) This means fewer quarts and less heat "reservoir" to keep things hot when you are in EV mode.

In fact, my recent observations show, that running cabin heat at medium or high settings will cut ( city ) mileage just as bad as using A/C in summer. You wouldn't think so, but field testing over the road proves this. Based at 32'F running cabin heat at a medium blower speed will cause engine temp to drop 1 degree every 4 seconds. Take a 2 minute stop light, and the engine will cool 30 degrees! This is often enough to drop it below the set-point for EV and the engine will come back on, dropping your MPG like a rock.

My advice? Treat cabin heater like you would the Max. A/C setting in summer. Ok to use for sustained driving, but turn cabin heat off ( or down as far as comfortable ) whenever your car goes into EV. Cabin heat will reduce your EV driving by 50-75%, and that is a substantial hit to MPG.

-John

 

I also put the system into recirculate mode to retain heat in the cabin. You use energy to heat outside air coming in when in 'Normal' air circulation mode. The downside to recirculate can be window fogging due to excess humidity in the cabin causing a periodic use of the AC compressor (defrost) or turning off recirculate for a while to dry the air.

JeffD

 

If you have a ScanGage installed, it will be an interesting reading. Turing the heater completely off can get the coolant up to normal operation in as little as half the time it otherwise would on a cold day.

 

I guess those heated seats may come in more handy than I thought....

 

I thought of that too, but I am worried that they could "suck" battery power pretty quickly when in EV mode.

 

I've suspected something like that for a while, hence I seldom use anything other then the lowest settings for the fans, which seems to warm things nicely after a bit and keep me EVing. I also tend to stay away from the maximum heat setting, instead a few notches above it, which I also think may have an effect.

 

The real answer is to add a 4-way reversing valve and change out the OEM compressor for an electric one powered a variable frequency AC drive so refrigerant pumping rate/volume will/can be equal to demand.

Now you have a HEAT PUMP and need not run the ICE for A/C or HEAT.

14,000 BTU portable air conditioner, heat pumps, can be purchased for less than $600.

 

Mine doesn't have a recirculate mode for the heater. Are you talking about MAX A/C? Wouldn't that run the compressor? I"m confused.

 

He's not talking MAX A/C but the setting below that where there is a little arrow going around in a circle. It won't run the compressor all the time but it will run when the ICE is on. In the end unless the windows are fogged up I'd think that would be a net loss in MPG.

 

Caution, DANGER..!!!

Do not, DO NOT, NEVER use recirculate mode during cold weather, even if the A/C is on (you think***).

You have no reliable human "sense", sensory perception, of the level of RH, Relative Humidity, that might exist within the passenger cabin at any given time. Once you close the passenger cabin to "forced" flow-through ventilation via the use of recirculate then the normal effects of human metabolism will soon result in the RH continually increasing, the more passengers on board, the faster the RH will rise.

The most likely follow-on scenario is that you will soon notice small wisps of condensation on the interior surface of the windshield, a windshield that is being continually CHILLED by the onslaught of COLD airflow on the outside due to roadspeed.

So, no sweat, you say, just activate the defrost/defog/demist mode, right?

Right.

The good part is that the system will now automatically switch to fresh incoming airflow mode.

Hint: If it doesn't then you had BETTER.


The bad part..??

Well...

Suppose the windshield started to fog over initially because many minutes ago you happened to drive into a climatic area wherein the OAT declined below ~35F and the A/C was accordingly SHUTDOWN.

The A/C CANNOT be restarted until the OAT rises above 35F.

All of the moisture remaining on the 10,000 square inches of evaporator cooling surface area due to previous A/C operation will now be "freed" to evaporate into the COLD (and therefore presumably dry) incoming airflow and thereby directly into the passenger cabin.

Additionally most newer climate control systems, predominantly so with the automatic ones with a temperature setpoint, rely EXCLUSIVELY on the A/C to dehumidify the system airflow to keep the cabin atmosphere RH below the dewpoint of the interior surface of the windshield.

***Some of these newer systems, Lexus and Toyota especially, will even leave the A/C "in operation" indicator lit even though in fact the compressor has been disabled due to low OAT.

So what happens when the A/C is disabled...?

Insofar as I have been able to learn the design engineers think it best that you not drive at all in those conditions.