Manufacturers aren't utilizing all options for efficiency IMO

[sportyaccordy]

For one, all the accessories shouldn't be belt driven... why not get a beefier alternator and have the A/C compressor & power steering pump be electric?

2, from what I understand Mazda has a feature that enables shutdown/start up of a gas motor w/o electric motors at stop lights. This is done through precise metering of fuel through DI. Combined with a larger reserve battery and the other features this could save a bit too.

A/C is a huge energy sapper... w/a bigger reserve battery and a DC/AC rectifier couldn't they do something more efficient than the belt driven system?

[Byteme]

My Mazda has an electric motor driving the power steering pump.  It's justified because in normal driving the power steering pump isn't used nearly as frequently as the AC compressor.

Air conditioning would require a fairly hefty electric motor, 8-10 HP, requiring a heavier alternator which would sap more energy from the engine to create the necessary current to run the compressor.  So a simple belt and compressor would be replaced by a heavier alternator, electric motor and wiring to power the compressor.   So you add weight and complexity and some conversion loses to try to solve a problem. 

[sportyaccordy]

To condition the air of a car cabin shouldn't require 10HP. The A/C in my bedroom prob only uses 1-2 HP at most. Looking at similarly sized units online yields that and my bedroom is 350 sq ft.

With an electric motor, yes you would lose some efficiency in converting but you would gain all that back and then some by having the compressor run at its most efficient speed.

[BimmerM3]

With an electric motor, yes you would lose some efficiency in converting but you would gain all that back and then some by having the compressor run at its most efficient speed.

But you're then adding not only an electric motor to the AC system (lolweight), but you'll need a bigger alternator (lolweight).

[Galaxy]

The BMW efficient dynamics package covers much of this.

[sportyaccordy]

But you're then adding not only an electric motor to the AC system (lolweight), but you'll need a bigger alternator (lolweight).

That could be offset by the smaller crank pulley + lack of complex mounts to keep the accessory belts in tension on all 3 components. I don't see that as much of an issue. Plus A/C gets used year round (dehumidification), so the cost benefits of a more efficient system would pay itself off in no time.

[93JC]

Plus A/C gets used year round (dehumidification),

Doesn't here.

[Raza]

They should change aircon to evaporation system.  No motors, no weight, no waste.

[AutobahnSHO]

They should change aircon to evaporation system.  No motors, no weight, no waste.

Doesn't work in high humidity areas..

[Raza]

Doesn't work in high humidity areas..

I wasn't being serious. 

[S204STi]

Doesn't here.

Many regions have higher humidy, and would need it most of the year.  In the winter your windshield will fog quickly and stay that way without dehumidification of the HVAC air blowing onto the base of your windshield.  Heck, even here at 5k feet I need to dehumidify the air during the winter months or else I get fogging as well.

[93JC]

Oh we get fogging in the winter too, but not because the incoming air is moist. The moisture in your breath condenses because the glass is so cold.

It's really cool when it's in the -40s and the condensation starts to freeze. I've had to scrape frost off the inside before.

[JWC]

Who needs a\c? 

[Raza]

Who needs a\c? 

Normal human beings.  I run aircon all the time.  I like it cold.  And up here, you get 90+F and 80+% humidity.  Even the dead sweat in that weather.

[AutobahnSHO]

I wasn't being serious. 

Why not?
It would work in Nevada, Idaho, and Wyoming..

[Byteme]

To condition the air of a car cabin shouldn't require 10HP. The A/C in my bedroom prob only uses 1-2 HP at most. Looking at similarly sized units online yields that and my bedroom is 350 sq ft.

With an electric motor, yes you would lose some efficiency in converting but you would gain all that back and then some by having the compressor run at its most efficient speed.

I just did a bit of research.  Teh consensus is car AC units use between 3-6 HP.

And like I said you would need an oversized alternator (more weight and drag on the engine) and an electric motor (more weight and underhood space taken) plus more wiring, a few more relays etc.

[S204STi]

Oh we get fogging in the winter too, but not because the incoming air is moist. The moisture in your breath condenses because the glass is so cold.

It's really cool when it's in the -40s and the condensation starts to freeze. I've had to scrape frost off the inside before.

Yeah, same issue here.  But dry air works better for defogging in any case.

[Raza]

Why not?
It would work in Nevada, Idaho, and Wyoming..

Don't you need an open water reservoir for an evap A/C? 

[GoCougs]

For one, all the accessories shouldn't be belt driven... why not get a beefier alternator and have the A/C compressor & power steering pump be electric?

2, from what I understand Mazda has a feature that enables shutdown/start up of a gas motor w/o electric motors at stop lights. This is done through precise metering of fuel through DI. Combined with a larger reserve battery and the other features this could save a bit too.

A/C is a huge energy sapper... w/a bigger reserve battery and a DC/AC rectifier couldn't they do something more efficient than the belt driven system?

Market studies I'm sure state that the 1-2 mpg savings isn't worth the moderate cost ($2,000+ I'd bet) for such motor systems.

The efficiency gains of running A/C compressor off of an electric motor will be minuscule as the normal course of operation the typical A/C compressor has a clutch that will cut out when need be.

Some efficiency gains can be found in oil pumps, PS pumps, water pumps, etc., but only because those systems either must run all the time, or do not have a clutch like an A/C compressor.

[cawimmer430]

Who needs a\c? 

Americans? 

[MX793]

But you're then adding not only an electric motor to the AC system (lolweight), but you'll need a bigger alternator (lolweight).

A bigger, more powerful alternator that is still belt driven and will now take more mechanical power to be turned.  And unlike the AC compressor, that saps the bulk of the mechanical power only when operating, the beefier alternator will be sapping more power 100% of the time the engine is running regardless of whether the AC is on or not.

[SVT666]

Oh we get fogging in the winter too, but not because the incoming air is moist. The moisture in your breath condenses because the glass is so cold.

It's really cool when it's in the -40s and the condensation starts to freeze. I've had to scrape frost off the inside before.

I believe Defrost uses the A/C compressor, but I could be wrong.

[Eye of the Tiger]

I believe Defrost uses the A/C compressor, but I could be wrong.

Most cars do this, and most people have no idea.

[the Teuton]

For you engineering folks, there's a technology available on many CDI diesels called Piezo injectors.  Essentially what it is is a valve that deforms when exposed to electric current, allowing for the injector to more efficiently distribute fuel into the cylinder.

It's really expensive technology, and I think the cheapest vehicle it's available in in the US is the F-350 Super Duty.  But it really does make a difference in power and efficiency.

[93JC]

Depends on the car. Some automatically kick on the A/C compressor, some don't. Mine doesn't. And obviously the cars out there without A/C still have defrost...

[Galaxy]

For you engineering folks, there's a technology available on many CDI diesels called Piezo injectors.  Essentially what it is is a valve that deforms when exposed to electric current, allowing for the injector to more efficiently distribute fuel into the cylinder.

It's really expensive technology, and I think the cheapest vehicle it's available in in the US is the F-350 Super Duty.  But it really does make a difference in power and efficiency.

The 335d and the Mercedes Bluetec fleet that are offered in the US have them.

[Eye of the Tiger]

Depends on the car. Some automatically kick on the A/C compressor, some don't. Mine doesn't. And obviously the cars out there without A/C still have defrost...

Yours as in yours Mazda3 doesn't? My Focus did. I unplugged the electrical connector on the back of the HVAC knob. A/C only goes on when I say A/C goes on! 

[GoCougs]

For you engineering folks, there's a technology available on many CDI diesels called Piezo injectors.  Essentially what it is is a valve that deforms when exposed to electric current, allowing for the injector to more efficiently distribute fuel into the cylinder.

It's really expensive technology, and I think the cheapest vehicle it's available in in the US is the F-350 Super Duty.  But it really does make a difference in power and efficiency.

Piezos also work in reverse - deform them and they produce a current - this is how click-style push-button ignitors work on grills and camping stoves.

[S204STi]

I believe Defrost uses the A/C compressor, but I could be wrong.

Most cars do this, and most people have no idea.

[the Teuton]

Piezos also work in reverse - deform them and they produce a current - this is how click-style push-button ignitors work on grills and camping stoves.

You learn something new everyday.