AC use penalty on 2007 Toyota Matrix

Discussion in 'Fuel Economy' started by MPGee, Sep 1, 2014.

  1. MPGee

    MPGee Active Member

    Thought y'all might be interested to know the results of some informal testing I did on how much turning on the A/C can cost on a 2007 Toyota Matrix.

    Based on my tests, it costs:
    10.66%

    Setup:
    Start from Park n' Ride center, and do an out and back drive on the (relatively) flat freeway here.
    Attempt to maintain 60 MPH as best as possible (My car doesn't have cruise control).
    Vehicle: 2007 Toyota Matrix, base. Mods: Passenger mirror delete, antenna delete, smooth hubcaps. Scangauge equipped, of course.
    Ambient temp during the test ranged from 84 to 96 (per my car's built in gauge).
    Distance: 21.2 miles on each loop.
    Condition A: No A/C, just outside air blowing in on fan setting 2 of 4.
    Condition B: A/C on, fan setting on 4 of 4, recirculate on.

    Run A1: 39.6 MPG, 0.53g, time 26:15, 48MPH avg
    Run B: 35.2 MPG, 0.60g, time 26:16, 48 MPH avg
    Run A2: 39.2 MPG, 0.54g, time 25:35, 49 MPH avg

    Average the two A runs to get 39.4 MPG. 39.4-25.3=4.2MPG. 4.2MPG/39.4 = 10.66%.

    Needless to say, I'm going to avoid running the AC from now on... :D

    -MPGee
     
  2. RedylC94

    RedylC94 Well-Known Member

    Interesting. That's pretty dang close to the 10.59% drop Andrew found on his Fit in a similar experiment.

    The percentage mpg drop could only be higher in an otherwise similar car with a lower drag coefficient, although the fuel consumption added by AC might be the same.
     
    Last edited: Sep 1, 2014
  3. 08EscapeHybrid

    08EscapeHybrid Moderator

    I find a/c hits me about 10% in the FEH. I minimize this hit by turning the a/c off while accelerating or going uphill. I've done several tests over the years in my 98 K1500, and I cannot detect any difference in mileage between a/c on and a/c off. My best guess is that the a/c is such a small draw on the overall power of the 5.7L V-8 that it really doesn't have to expend any additional effort to turn the a/c compressor as well.
     
  4. jcp123

    jcp123 Caliente!

    Wow. Ac seems to cost me more than that...
     
  5. Mendel Leisk

    Mendel Leisk 2010 Prius (CAN Touring) Staff Member

    At Priuschat there's a virtual consensus that AC in hot weather is good for the hybrid battery, and has minimum impact on mpg. I'm not so sure.

    At the suggestion of some AC proponents there, I managed to install the ScanGauge XGauges for battery temp and fan speed. The worst case I saw for battery temps was one hot day when we'd parked after a drive, then after a hot soak came back for a further drive.

    Battery temp was into the 40's (C) and fan mode 4 (out of 5 or 6?). After a few miles drive without AC, rolled up the windows and set it on AC auto, with temp around 25 (C). In the course of a further 10 miles or so, battery temp barely budged, 1 or 2 (C) at most. Ambient temp was around 30 (C). Maybe with higher temps the drop would be more significant, not sure.

    My seat-of-pants observations of AC's impact on mpg are similar, around 10%. We're continuing to use it very rarely through summer, more throughout the rest of the year, particularly when it's the last resort to clear steamy windows.

    Owner's Manuals typically caution to use it at least occasionally, to keep oil in the lines circulating, which in turn keep the system's rubber gaskets pliant.
     
  6. jcp123

    jcp123 Caliente!

    The suggestion about using ac occasionally is valid. I turn it on once a month for a minimum of 10 mins to keep the oil circulated. Usually on the highway, as the penalty in-town is closer to 30% for me, but only around 10%-15% on the open road.

    The one question I have is, does keeping the blower set to a lower setting improve FE performance? I don't really use it enough to know - I don't use it for my own comfort, usually the family is in the car with me when it's on. It's not a very strong ac unit, so it usually stays on full blast. But the little experimentation I have done suggests am improvement. This is plausible for me as not as much heat energy is being absorbed back into the freon, causing the compressor to cycle less. Valid observation?
     
  7. phoebeisis

    phoebeisis Well-Known Member

    In NOLA- no choice-

    I think the penalty might be a tiny bit less(hy 60 mph) with the 1998 Suburban-despite the HUGE interior volume-and all the windows

    In the city I will sometimes flick it on while gliding-a glide where I KNOW I am going to brake-perhaps it helps

    But 10%- yeah car Acs are probably several Tons capacity-
    3 tons-3000 watts or so- 4 hp
    yeah 4 hp-probably doesn't take much more than 20 hp to keep a Matrix at 60 mph(pure guess)

    Anyone know the capacity of a car AC- 12,000 24,000 btus?? Pretty sure the 1960's claim was an AC "took" 5-6hp "You need a V-8 if you option AC" the sales folks would claim
    so 10% is better than expected
     
  8. RedylC94

    RedylC94 Well-Known Member

    I don't know all the particulars, but it makes sense that the a Prius's electrically driven AC would consume less energy (despite added conversion losses), because the compressor speed is under control, not at the mercy of highly variable engine speed.
     
  9. Mendel Leisk

    Mendel Leisk 2010 Prius (CAN Touring) Staff Member

     
    Last edited: Sep 2, 2014
  10. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    Yeah... pretty sure the Matrix and Echo don't have automatic climate control. Nor does my Fit. (the Ody does)

    But there is a common bit of backwards programming in most automatic systems. You climb into the hot car and it's 120F inside. Outside it's 95F. It defaults into Max mode which recirculates interior air. Once it's cooled down a bit, it switches to outside fresh air.

    It starts out pulling in 120F air, and only switches to the cooler 95F source when the interior is cooler than 95. :confused:
     
  11. jcp123

    jcp123 Caliente!

    That's strange...why would it pull the hot air??

    And no, I don't have auto climate control...

    But the consensus is that a milder setting for the ac does improve FE!
     
  12. Die2self

    Die2self Saving more by using less!

    I would think that having the blower on max will not only get your car cooler quicker but the opposite. If you think about the converter, the longer the air has to move over the condenser, the cooler and less humid the air will be coming out of the vents. Thus if the air is always barely in contact with the condenser, the less cooled the air will be and more moister will be held in the air.

    I usually start off by opening the windows while walking up to the car or just after I get in it. Let most of the hot air out for a few blocks, then Hit the AC (if I use it with the family), roll up the front two windows, roll up the back ones to a crack to allow a little more hot air out as it is forced out by the AC air.

    Blower is usually 50 - 75% for a few minutes to circulate the cooler air. Then turn it down to 50%-40%. The Accord really works great on the highway and will freeze you out if you let it sit up that high. I is usually pulled back to just barely on. In town it usually stays at about 40% blower and into recirculate (because fumes and temp) to keep the cool air in the cabin.

    I would have like to see the AC run be set at the same 2 out of 4 setting instead of on MAX blower. I should cycle on and off less often with lower blower speed.
     
  13. jcp123

    jcp123 Caliente!

    I do wish my ac were more effective. It's adequate an emo more than that. I hooked up a set of manifold gauges and found that high side pressures were only about 10psi below the low spec. Perhaps it needs a bit of refrigerant but as the whole thing holds only 16oz. I'm not going to buy a 12oz can to use 1 or 2oz.
     
  14. 08EscapeHybrid

    08EscapeHybrid Moderator

    If its hot out I usually roll all windows down, and turn the a/c on, blower on high, not recirculating. After about a block where the hot air is blown out of the ducts, and the worst of it is out of the car, I roll up the front windows. About a block later I will roll up the rears to about 1" shy of closed and let the a/c push out the remainder of the hot air in the car.

    I find in the FEH that if I leave everything in full auto mode, the blower cuts back to low, and heat starts building up in the back. I will usually leave it set for auto thermostat, but manual fan speed of about 40% so cool air circulates in the back, and the whole interior is cool. This is important as I let the engine shut down at slow speeds and at stops, and that means the compressor is stopped too. The interior stays comfortable a lot longer if I'm not starting out with hot air in the back when the engine & a/c shut down.
     
  15. WriConsult

    WriConsult Super Moderator

    I've found AC to cost me at least 10%, maybe even a bit more, in city driving. However, the penalty on the highway seems to be considerably less: on both the Elantra Touring and the Mazda5, just 1-2mpg out of 35-45mpg.
     
  16. The Doctor

    The Doctor Old Dude, New Car

    On my 2013 Kia Soul, I have the little 1.6L engine. It's a real power house, but......
    it can only put out just so much horsepower and as accessories are turned on, MPG will go down.

    Using my Scan Gauge II, to monitor my MPG in real time, I've turned my AC on and off many times and every time I get the same results. My highway MPG will drop by 3 mpg, when I turn the AC on and increase again by 3mpg, when I turn the AC off.

    But I like my creature comforts, so the AC is ON most of the time, in the summer anyway.
    And I use the AC in colder weather, to de-fog the windshield.

    You not only get what you pay for, but..... you pay for what you get.

    The smaller the engine, the more difference in MPG you'll see between AC on and AC off.

    Cheers Mates and Happy Holidays

    The Doctor :cool:
     

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