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Old 08-10-2011, 02:14 AM   #63 (permalink)
Hatchtastic
EcoModding Lurker
 
Join Date: Sep 2009
Location: Colorado
Posts: 28

'Stache Builder - '92 Honda Civic VX
90 day: 42.58 mpg (US)

White Dwarf - '09 Mazda 5
90 day: 28.87 mpg (US)
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As an automotive technician I will also confirm that your AC stayed on for that trip. Many new cars keep the AC on to de-humidify the incoming air, and with re-circulate selected.

AC systems cycle on and off by themselves based on cooling load (demand). You really shouldn't have to be switching your AC button on and off, just turn the fan down. If you have a low fan setting, it will not be taking much chill off the evaporator core, and the AC clutch will shut off from lack of cooling demand. AC systems have pressure switches to control their on and off times. If you don't demand much cooling, the pressure differential from the high side to the low side will cause the compressor clutch to turn off. On a cold day, your AC won't cycle on as much compared to a hot day, due to less cooling demand. At least that's how it works in my mind . I'm not sure if you could also reduce cooling load by turning the temperature blend a bit warmer if the lowest fan setting is still too cold. It makes sense that it would, because you are drawing even less air across the evaporator (depending on system design). This would all be interesting to test for someone with a ScanGauge. Do some A-B-A-B testing with manually cycling AC (pulse-and-gliding AC?) vs. using a very low cooling demand setting (low fan and/or warmer blend).
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1992 Civic VX


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