Heat and the winter
Active Enthusiast
Joined: Sep 2006
Posts: 124
From: Northern Virginia
Re: Heat and the winter
Actually the AC compressor does not put a strain on the engine directly as it does in most cars. There's no direct connection (belt) for the AC Compressor on a TCH. It is driven (always) via it's own electric motor. Hence the reason a TCH can run it's AC while in EV mode.
Randy,
Thanks for the info; it makes sense to me. I am confused, however, by the number of posts I think I read earlier in the year about people stating they try to improve FE by limiting A/C use. Are they (like me) misled? If so, maybe there is a case to be made for running in AUTO mode. One reason I don't do it now because I don't like the A/C coming on when I'm running the heater or when I want vent air.
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Active Enthusiast
Joined: Oct 2006
Posts: 63
From: Linwood, NJ
Re: Heat and the winter
Randy,
MPG appears to be 2mpg better in the fall with windows closed and HVAC off. No theory other then with a conventional car is the same. In theory this should not be true, if AC only ran off the battery, it must not be how it runs when using the gas engine.
Josh
MPG appears to be 2mpg better in the fall with windows closed and HVAC off. No theory other then with a conventional car is the same. In theory this should not be true, if AC only ran off the battery, it must not be how it runs when using the gas engine.
Josh
Currency-to-hydrocarbons
Joined: Sep 2006
Posts: 343
From: Minneapolis, MN
Re: Heat and the winter
Randy,
Thanks for the info; it makes sense to me. I am confused, however, by the number of posts I think I read earlier in the year about people stating they try to improve FE by limiting A/C use. Are they (like me) misled? If so, maybe there is a case to be made for running in AUTO mode. One reason I don't do it now because I don't like the A/C coming on when I'm running the heater or when I want vent air.
Thanks for the info; it makes sense to me. I am confused, however, by the number of posts I think I read earlier in the year about people stating they try to improve FE by limiting A/C use. Are they (like me) misled? If so, maybe there is a case to be made for running in AUTO mode. One reason I don't do it now because I don't like the A/C coming on when I'm running the heater or when I want vent air.
Relative to the current discussion - The voltage / current being consumed by the AC Compressor's electric motor must be replenished via the Motor Generator system. This will cause an additional (albeit slight) load on the ICE..
Given the extremely high efficiency of the AC compressor and system in general, I don't think you'll notice much (if any) difference in fuel economy.
Another good reason to run the AC compressor periodically is because the lubricant for the compressor is mixed in with the Freon (or in our cars R-134). If left to sit for long periods of time, the oil will settle out and take longer to circulate once you turn the AC on - this will cause more wear in the system and less overall efficiency.
Currency-to-hydrocarbons
Joined: Sep 2006
Posts: 343
From: Minneapolis, MN
Re: Heat and the winter
2mpg is substantial - even more than I observed in our Honda Civic when I tested FE AC on vs AC off. I was able to get only 1mpg better FE on a 500 mile trip with running FAN only (no AC compressor - wire disconnected)..
Ridiculously Active Enthusiast
Joined: May 2006
Posts: 685
From: San Diego
Re: Heat and the winter
No, turning off the A/C will improve the FE (I notice about a 2 to 3 mpg improvement.) Think about it. The A/C uses electric power. The power has to come from someplace. The only sources of electric power on the TCH are the ICE, regen during costing/braking and the hybrid battery. The ICE will use more gas to make up the power used by the A/C. It just might not be noticable immediately if you have a high SOC on the hybrid battery.
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