Which accessories cause MPG to suffer most

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#11

01-04-2008, 04:46 PM

spartybrutus

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Re: Which accessories cause MPG to suffer most

Isnt the ICE on the top of the TCH (or Prius) list? It really is an "accessory" that gets used only when the elec motor/battery can't propel the vehicle fast enough

#12

01-05-2008, 07:59 AM

schmidtj

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Re: Which accessories cause MPG to suffer most

Quote:

Originally Posted by spartybrutus

Isnt the ICE on the top of the TCH (or Prius) list? It really is an "accessory" that gets used only when the elec motor/battery can't propel the vehicle fast enough

Well I think an accessory is something I, the driver, can control directly. The ICE has a mind of it's own. Using your logic the fuel pump would be the worst offender but alas it too is not an accessory.

#13

01-05-2008, 10:17 AM

spartybrutus

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Re: Which accessories cause MPG to suffer most

Yep, youre probably right - its tough to avoid having the ICE "wake up" although your right foot may control how "awake" it is.

AC is probably top of the list then...

#14

01-05-2008, 07:42 PM

Mystifier

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Re: Which accessories cause MPG to suffer most

Quote:

Originally Posted by SPL

The AC is by far the biggest accessory drain on the NiMH battery — over 6 kW at full cooling, if I am remembering correctly. Don't forget that the AC runs from the high-voltage battery for this very reason! Also bear in mind that all the energy used ultimately comes from the gasoline. The ICE recharges the NiMH battery, and the NiMH battery recharges the 12-V battery.

Stan

If that's the case I wonder why Toyota made it so AC comes on by default when setting the climate control to Auto. I always turn it off as soon as I hit Auto. Seems to me like AC should only be turned on when it is needed, not 'On' by default.

#15

01-06-2008, 03:01 AM

haroldo

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Re: Which accessories cause MPG to suffer most

Quote:

Originally Posted by Mystifier

It might be due to the way Japanese cars are set up to handle air circulation.
The air (recirculated) needs to be dehumidified, which requires the AC system.
Found this information here.

Quote:

AutoTips Defrosting Tips

Does the defroster on your Japanese car not seem to be doing as well as it should? There may be several reasons.
If you have an imported car::
Check the air control lever in the heater controls that selects Fresh or Recirculate. The indicator plate around this lever normally has two positions indicated by arrows showing air entering the car, or going in a circle. For defrosting it should be in the position to bring in fresh air. This is probably the most common reason people's Japanese defrosters do not work well, they have the air position lever set to re-circulate. Recirculated air holds moisture we breathe out, and it condenses on the windows.
For best defrosting on an import: select Fresh Air, and turn on the Air Conditioning, with the temperature lever to your desired comfort level. The air-conditioner de-humidifies the air before heating it. Air Conditioning can help remove humidity from the air. On many import cars there is a separate button to turn on the Air Conditioning. With the control set to defrost, you can turn on the A/C on days above freezing to remove humidity from air and help remove frost of the windows. The air can still be heated by adjusting the temperature lever to warm. The Air Conditioner switch is separate on some imports, built in to the heat / ac / defrost lever on most domestic cars.

U.S. model cars: Most U.S. cars bring in fresh air and turn on the air conditioning when defrost is selected.
...

Last edited by haroldo; 01-06-2008 at 03:05 AM.

#16

01-06-2008, 04:12 AM

schmidtj

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Re: Which accessories cause MPG to suffer most

Quote:

Originally Posted by Mystifier

Just because the A/C light is ON does not mean the A/C is actually running. It just means the climate control system CAN turn on the A/C if it needs to. If you defeat this by manually turning off the A/C button you disable the systems ability to dehumidify the air when needed etc.
That said, my '07 XLE-V6 in AUTO mode the A/C light does not illuminate when it is very cold outside. Like there is a lower limit to the outside temperature below which the A/C is disabled. Makes sense since the XLE uses the older mechanical/rotary compressor whereas the TCH uses the electric powered variable speed(?) compressor.

Last edited by schmidtj; 01-06-2008 at 11:51 PM.

#17

01-06-2008, 11:06 AM

n8kwx

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Re: Which accessories cause MPG to suffer most

Quote:

Originally Posted by SPL

The AC is by far the biggest accessory drain on the NiMH battery — over 6 kW at full cooling, if I am remembering correctly.

The TCH (and Prius, etc) AC compressor is variable speed. So while it may draw up to 6kW peak, it will often run at much lower power. It only uses the power it needs.

I see much larger drops in mileage due to the heater. In the summer the AC hardly affects mileage. The ICE will run unnecessarily to keep the heater core warm.

#18

01-06-2008, 05:21 PM

Mystifier

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Re: Which accessories cause MPG to suffer most

Quote:

Originally Posted by schmidtj

Just because the A/C light is ON does not mean the A/C is actually running. It just means the climate control system CAN turn on the A/C if it needs to. If you defeat this by manually turning off the A/C button you disable the systems ability to dehumidify the air when needed etc.
That said, my '07 XLE-V6 in AUTO mode only illuminates the A/C light when the mechanical A/C compressor is actually engaged. This is different from the way the TCH works the A/C light.

Interesting info! Do you know what level of humidity the climate control on the TCH tries to maintain?

#19

01-07-2008, 10:55 AM

SPL

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Re: Which accessories cause MPG to suffer most

schmidtj is right — the fact that the AC light is on does not imply that the AC compressor is actually running, just that the system can use it if it so wishes. At very low temperatures, there's a possibility of freezing in the AC refrigerant lines, and so the AC is disabled. In my old 1993 Camry, the AC light would stay on at these low temperatures, but the AC compressor would not run. The TCH may behave the same.

n8kwx is also right — the AC compressor is a variable-speed unit. It uses less electrical power when it's running at low speed. But it certainly does use power that has to ultimately be replenished by consuming gasoline.

Stan

#20

01-08-2008, 07:18 PM

finbib

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Re: Which accessories cause MPG to suffer most

Quote:

Originally Posted by n8kwx

I see much larger drops in mileage due to the heater. In the summer the AC hardly affects mileage. The ICE will run unnecessarily to keep the heater core warm.

I agree with that. Here in IL, the temps went from about 60F to 25F to 10F without blinking an eye, right before Xmas. My FE went thru the floor, right with the temperatures. 39.5 MPG down to 35.5.

I often use the defrost/heat only for the amount of time it takes to clear the windows, and use the seat heater heat my body instead of running the heater to try to improve the gas consumption. Then I'll put it on Auto, and put the ECO back on.