Poor fuel economy over short distances

[TimRogers]

Older thread but everything is still relevant; I've tried to search to see if anyone else is doing this and haven't seen anything.

I have a 4 mile commute; in the morning I can use the block heater at home but I have no place to plug in at the open parking lot at work.
So, I've been trying to use the sun and my brain to give the engine temperature a little boost by drawing the heat inside the car into the coolant.

When I park the car after I get to work, I set:
The HVAC controls to Recirculate so the only air going over the heater core is from the sun warmed interior.
Vents to Bi-Level to encourage air flow through the heater core as the car interior warms in the sun.
The temperature to Hot so that the heated water from the heater core will flow into the engine block (but the thermostat won't let it go to the radiator).
I also set the fan to High so that when I start the car, the heat of the interior is immediately transferred into the coolant with maximum effect.
When I get in the car and turn the ignition on 9.5 hours after I parked it, I'm seeing coolant temperatures 5 to 10 degrees above the exterior temperature. Not a huge increase but any improvement is an improvement.
As I drive, I watch the coolant temperature increase and as soon as it increases over what I feel the interior temperature is (maybe I should put a thermometer in the cabin to be more precicse) I move the temperature control to full Cold and adjust the other controls as needed for personal comfort until the engine is fully warm.

It probably helps that I have an older car with cable actuated HVAC controls; cars with vacuum actuated HVAC systems may benefit from setting the controls in the last moment before shutting the engine off? Also, some vehicles will automatically engage the A/C compressor with certain HVAC settings; they may need to change the settings before starting the vehicle.

One added benefit as we move into the warmer spring and summer months is that I'm pulling heat out of the cabin and moving it into the engine throughout the day.

[RedDevil]

That's smart! Setting the heater to max when the interior is hot while the engine is still cold actually cools the interior.
I'm going to try that out for sure, see if the engine temp does rise faster like that (on my UltraGauge). If I ever get to drive again

[Tahoe_Hybrid]

about as good as my V8 6.0L hybrid 20.5 in the city

[Isaac Zachary]

Interesting idea! I've thought about routing inside air to the intake so it'll suck in warm air. That should help the car to not need to run as rich during startup, in theory anyhow.

[Piotrsko]

Except for the large current battery requirements, there are 12v powered heat units in my F250: fuel bowl, glow plugs. In the ranger, I spliced in a solar panel 1000 watt 12v water heater into the coolant line since the electric motor doesn't have water cooling.

[TimRogers]

Originally Posted by Isaac Zachary

Interesting idea! I've thought about routing inside air to the intake so it'll suck in warm air. That should help the car to not need to run as rich during startup, in theory anyhow.

Yes, assuming your car has an Intake Air Temperature Sensor.

[elhigh]

I honestly never thought of doing this, reverse thermosiphon to pull heat out of the cabin.

I wonder if a solar power muffin fan pulling air through the system while parked would help?