Reducing the energy loss due to A/C

[rbrowning]

Why do car makers not heat and cool our cars like we do our homes? In my home during the summer, I don't regulate the temperature in a room by running the A/C all of the time and when it gets too cool I turn on the furnace, I just turn off the A/C. Why do we regulate the temperature in our cars by running the A/C all of the time at maximum power then moderate the temperature with hot water from the engine. Why not automatically cycle the A/C on and off to maintain the temperature like your furnace does at home in the winter?

This is the technique that I use to help reduce fuel consumption, but making it automatic would allow the manufacturer to raise their CAFE ratings.

I'm sure that it wouldn't cost too much since you already have temperature sensors all over your car already. And software doesn't add weight.

[Arragonis]

The hot water from the engine is there all the time anyway, so no additional energy in making that.

Some cars with climate control with air con do that automatically - turn the AC on and off. You can cycle your air con manually to do the same thing. I've seem some advice about not running it when accelerating in a low power car.

[cfg83]

rbrowning -

What Arragonis said. Newer cars (not mine) are cycling the A/C to save fuel.

CarloSW2

[autoteach]

Pop your hood and run your AC full tilt. You should see the AC clutch engage and disengage as needed. This does mean that the AC is not running all the time. As for heat, like it was said above.

[Phantom]

Some cars also control the A/C by TPS% although the ones I have seen are set to high (from factory) like turn off at 94% throttle.

[rbrowning]

I realized that the heat was "free", but I was not aware that the A/C compressor was cycling. I turn mine off and on manually to maintain a reasonably comfortable temperature and have been doing so for years. I have never heard my engine speed change so I'm not sure if the A/C isn't drawing much power or if it isn't cycling off and on.

[gone-ot]

TSV = "Throttle Suction Valve" modulation, for those wondering.

...part of "automatic" A/C control system; TPS is part of "engine" control system.

[Phantom]

TPS = Throttle position sensor

Or at least thats the only way I have seen it used.

[ShadeTreeMech]

Originally Posted by rbrowning

I realized that the heat was "free", but I was not aware that the A/C compressor was cycling. I turn mine off and on manually to maintain a reasonably comfortable temperature and have been doing so for years. I have never heard my engine speed change so I'm not sure if the A/C isn't drawing much power or if it isn't cycling off and on.

Your method of manually cycling on and off does work most economically, but it can get annoying on a long trip.

In my van (with manual controls) I run the blowers until a comfortable temp is reached, then turn the blowers down to minumum setting. There are temp sensors designed to keep the condensor from freezing up, and by slowing down the air flow, the condensor gets cold faster, and cycles the compressor off more frequently. Most of the time this maintains a comfortable temperature.

[euromodder]

Before I had cruise control added to my car, I had never been able to spot a difference in FE with or without airco.
On CC however, fuel consumption will instantly drop 0.2 to 0.3 L/100 km - around 6% - when shutting the AC down - that's a 3 mpg increase in FE.