When I was in my Insight, I never found a speed (I was willing to drive at) that the AC on was more efficient than the windows down.
I agree. I think running the A/C compressor makes lean burn much more difficult to maintain which impacts highway fuel efficiency much more than increased aerodynamic drag with the windows open. But that's only a gut feeling…
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Aloha,
Art Isbell
2000 Insight A/C #559
Genesis One MIMA+FAS and grid charger, OBDIIC&C, Rostra, Fumoto, DEFA engine block heater, Philips LED DRL's, Honda security system
For most of my driving above about 40 mph I find that I get good airflow with the windows up almost all the way, keeps the buffeting and wind noise down but I still get good airflow.
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2001 Red CVT
19,351 miles lmpg 19.0 as of Oct 7, 2011
Best tank 78.9 MPG, 738.9 miles
Email dave@groe.us
A/C is big hit as we know esp. in cars with lean-burn. But there are techniques to reduce the hit. I always try to use the fan first. If it gets too hot I turn it on with recirculation set at the coolest temp with low fan. The I1 has not an intelligent A/C compressor with variable compression ratio like todays Audi for example has. So, if you set mid temps and high fan wam air from the engine will be mixed. That's not efficient at all.
If I know that there are hills on my way I don't use it uphill but use it downhill. Sometimes the hill is so steep that I can get A/C for free as I had to use the brakes anyway.
So, if you set mid temps and high fan wam air from the engine will be mixed. That's not efficient at all.
You can disconnect the cable for the heater coolant valve. Its under the hood near the firewall on the left of the battery. Just unhook it (while in the closed position), and hot coolant wont circulate inside the heater core any more, and you can set the temp dial anywhere, and it will blow cold air, but as you turn it higher, it will cycle the compressor less. With it disconnected, I usually keep the a/c on 70-75, and the compressors turns on much less frequently, and no mixing of hot air.
I had to shoot out to Arlington yesterday, in 109° heat (!), AC on my normal Econ/72° (I have seldom turned it off), 95% highway at 70-75mph. As is my habit, I zero'ed the trip odometer upon departure, and here is what my results were when I returned home and parked my CVT Insight back in the garage:
For those not familiar with my other habits: 50# psi in each corner, no cruise, no drafting other cars, ScanGageII to monitor metrics in real time.
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Driving on down the road in my 2001 CVT, going "Boogety Boogety" ...and until avatars are provided, my car looks just like the original silver Insight on the header, above... =)
Tuesday I had an errand to run and drove 38 miles getting 83.1 mpg (cvt, not manual trans). I had the hvac off, and the windows down, was real hot but doable. Later in the day I went out with my wife and had to run the ac for her. I only got in the low 60s for mpg. That was nearly a 20 mpg hit just due to the ac.
The best I get is 58 MPG summer and a low of 48 MPG cold winter in Ohio. Not sure how to get your 83 MPG, perhaps I need to change something? I have a 2004 CVT with 89,000 miles currently.
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