Fuel Economy while aircon is used?

[Cheap6]

will notice it a fair bit at idle using the instant fuel use,

while driving wont nealy make any difference in fact, if your clever, everytime you coast down hill, or engine braking, with your foot off the trottle, turn the air con on and enjoy free cold air...... results will best come from a manual gearbox though

Absolutely. If it gets to be a pain switching the A/C on and off all the time maybe consider the following: I have a switching circuit I built that means I can have the A/C operate only when the brake pedal is depressed. There is about 7-10 seconds of hysteresis built into it so a brief brake application doesn't switch the A/C on then immediately off. (The hysteresis keeps the A/C on after a touch of the brakes.) There is enough free travel in the brake pedal that the brakes don't even have to be used to get the A/C to come on; a brush of the brake pedal is sufficient. There is also an over ride switch for highway use where there is not much braking.

An alternative is to switch the A/C out at lower than standard (the A/C is off at WOT) throttle openings. That means the A/C is off for more than the usual duty cycle time and helps load balance the engine and have it operate in a more efficient way more often. There is an Autospeed article on how to do that.

You can also play with the amount of recirculated air. I'm sure it's possible to calculate the most efficient amount of recirculated to fresh air but just using some of each will more likely be more efficient. (The most efficient amount will be affected by inside and outside air temperature and humidity.)

 

[andyman]

Absolutely. If it gets to be a pain switching the A/C on and off all the time maybe consider the following: I have a switching circuit I built that means I can have the A/C operate only when the brake pedal is depressed. There is about 7-10 seconds of hysteresis built into it so a brief brake application doesn't switch the A/C on then immediately off. (The hysteresis keeps the A/C on after a touch of the brakes.) There is enough free travel in the brake pedal that the brakes don't even have to be used to get the A/C to come on; a brush of the brake pedal is sufficient. There is also an over ride switch for highway use where there is not much braking.

An alternative is to switch the A/C out at lower than standard (the A/C is off at WOT) throttle openings. That means the A/C is off for more than the usual duty cycle time and helps load balance the engine and have it operate in a more efficient way more often. There is an Autospeed article on how to do that.

You can also play with the amount of recirculated air. I'm sure it's possible to calculate the most efficient amount of recirculated to fresh air but just using some of each will more likely be more efficient. (The most efficient amount will be affected by inside and outside air temperature and humidity.)

thats just thinking about it too much......... only design floor in the braking thing for you would be if your car is an auto...... unless the torque converter is locked an auto equiped motor will use fuel under de-accell anyway

 

[RiCeY]

Geez people if youre that worried about minimal increases in fuel consumption for some comfort maybe use public transport!!

 

[andyman]

Geez people if youre that worried about minimal increases in fuel consumption for some comfort maybe use public transport!!

my thought exactly.... its hard to make a comment look smart assed on the internet haha

 

[Cheap6]

thats just thinking about it too much......... only design floor in the braking thing for you would be if your car is an auto...... unless the torque converter is locked an auto equiped motor will use fuel under de-accell anyway

Autos still have the fuel cut on decel..

Geez people if youre that worried about minimal increases in fuel consumption for some comfort maybe use public transport!!

It's real money for not much effort (actually, fun rather than effort). A 5% fuel saving is easy. That's $100-150 per year, depending on how much use the A/C gets. Better off in my pocket than in the oil companies'.

 

[gossie]

Geez people if youre that worried about minimal increases in fuel consumption for some comfort maybe use public transport!!

Absolutely. Amazing how a lot of people forget that fuel for your vehicle is one of the lowest cost things.

 

[monkeys437]

Absolutely. Amazing how a lot of people forget that fuel for your vehicle is one of the lowest cost things.

Only for new cars. For people like me (tightarses) I would think Fuel is bigger than every other ownership cost put together

 

[Cheap6]

While it depends some on what, how far, where and when you drive it's still a couple of grand a year. eg. 17000km/yr @ 12l/100km @ $1.30/L = $2652/yr. You don't have to reduce that by a very big percentage for it to be worthwhile.

The A/C brake switch (^) took < 1 hour to knock up from bits in the parts box, so zero (extra) outlay. So I got an hour's entertainment and get "paid" for it for as long as I drive the car. That's a pretty good deal. Even if I had to buy everything specially it would only be ~$40.

 

[CONROD]

Geez people if youre that worried about minimal increases in fuel consumption for some comfort maybe use public transport!!

My thoughts exactly!!
Its not like in the olden days where you turned the A/C on and your car dropped 500rpm from the drag of the compressor cutting in

:idea3:Wind the windows down and eat a bloody ice cream

 

[RiCeY]

Autos still have the fuel cut on decel..



It's real money for not much effort (actually, fun rather than effort). A 5% fuel saving is easy. That's $100-150 per year, depending on how much use the A/C gets. Better off in my pocket than in the oil companies'.

So thats $2.88 a week maximum. If money is that tight that $3 a week makes a difference there a serious problem.