Questions on Camry MPG? Possible Answers

Discussion in 'Toyota Camry Hybrid' started by Dan, Aug 5, 2008.

  1. Dan

    Dan KiloTanked in post 153451

    Received this question on the Welcome Thread.
    Sound like accessory load to me. The AC in this car is pure electric and when on will draw as much as 5 Amps (that's a lot). Headlights will draw another Amp or two, and a huge car stereo system could add even more wood to the fire.

    When there is a heavy accessory load on the battery the charge can get low and the battery icon in the energy screen can show as less than half full or purple. When the batter approaches the half-full mark the RPMs will spike. This is because the battery is trying to keep it's charge high and is asking to engine to rev high to redirect power to charging the battery.

    My suggestion would be to do the following.
    1. Note how many miles are on the car. The "MPG" break-in period is about 5,000 miles.
    2. Bring your tires up to the maximum sidewall pressure for the following experiment.
    3. Have your tire wear and tread depth checked for even-ness
    4. Have your alignment and tire balance checked.
    5. Note tire brand and make if they are not the original OEM tires.
    6. Get a fresh oil change and provide your own oil (Mobil-1 0w-20 only).
    7. Have the fill level checked to ensure that the oil level is halfway BETWEEN the LOW/FILL line and the HIGH/FULL line on the dipstick.
    8. If you have high power audio/video/entertainment system in your car, inquire if there is a fuse you can pull temporarily to prevent it from drawing power.
    9. Replace your air filter with the prescribed Toyota air filter (cheep).
    10. If the spark plugs have been replaced, inquire as to what type of plugs were used.
    11. Ensure that the last gas purchase was not E85 or E15, only Regular (not Premium) unleaded (with up to E10) is supported in the TCH.
    12. While driving ensure that the transmission is in "D" Drive and not "B" Brake.
    13. Ensure that vents to the battery (under the rear window) are clear of debris and clean of any dust, lint or pet hair.
    14. Empty your trunk of any material to ensure proper ventilation of the battery.
    15. If an audio/video/entertainment system is installed in the trunk, insure that it was not drilled into the battery housing.

    Once you've tried that see if you can find a 5 mile stretch of FLAT road without lights or stop-signs. Drive the TCH on the highway for 30 minutes to warm the engine and charge the battery to at least 6 blue bars. Now go to your flat road and set the Cruise Control to 52 MPH with AC off, windows up, radio off, headlights off, and minimal accessory load. You should see MPG in the high 40's to low 50's for your test. If so, you've fixed the issue with one of the above chores.

    Lot of junk, so bounce back with questions or concerns about the how's or why's with any of the steps above.

  2. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi All:

    ___A new guy with little idea as to the ways of hypermiling pulling 30 mpg is about right. Especially on a short segment as he did not mention that?

    ___Tire pressure and not knowing how to turn off his A/C is possibly where he needs to start.

    ___Where is his thread located anyway?

    ___Good Luck

  3. Dan

    Dan KiloTanked in post 153451

  4. caplanjr

    caplanjr New Member

    Thanks for the list, Dan.
    I did most of those things before I posted. Remember, it's a BRAND NEW CAR -- fewer than 2k miles, so no oil change yet (next week), no pet hair, aftermarket stereo, etc. We'll test the accessory load theory in a couple of months after the temperature in DC drops under 92 with 80% humidity! Anyone know what 5 amps means in terms of mpg? Next week, the dealer is hooking up a stack of diagnostic gear and driving the car for two days. I'll report back to the group. This car is a joy to drive -- now if we can just get the mpg into the forties...

    Regards and thanks, everyone.
  5. Dan

    Dan KiloTanked in post 153451

    Very good to hear.
    Ahh! you hadn't mentioned "new" in the post.
    92 should be fine with the windows down. Things don't start getting dicey till you hit 102 (Texas winter).
    About 20% hit to MPG, but it gets much more substantial since the AC disables the Hybrid drive train in the Camry. Technically you can drive with AC, but it requires some gauges. Without getting too technical, you have to pulse the AC off whenever you want the engine to cut out. If you haven't forced a stage transition though it's hopeless. Once you do get the engine to cut you can turn the AC back on, and provided that you have sufficient charge in the pack, the engine won't light.
    I don't personally think that is necessary. I'm 100% sure that it's A/C coupled with stage transition. But if you do get the dealer to look at it, get them to drain the excess oil from the pan. Every NEW Toyota Hybrid I've spot checked at the dealer is overfilled with oil (oil above the "FULL" line).

  6. jmonti

    jmonti Member


    Thanks for all you do on this site and promoting hypermiling. As an owner of a TCH for just over one year now I'd like to re-state what Wayne mentioned earlier. One of the biggest hitters to the TCH's MPG is short trips. In warm weather I regularly do high 40's/low 50's on my 22 mile commute. However, the 1.5 mile trip to my parents is a killer when the engine is not yet warmed up. We never got an answer as to what the commute in the original post looks like.

    Another thing I'd like to "complain" about is the "wonderful" job all the car companies, including Toyota, are doing misleading the public. Every car ad on TV states the highway mileage and conveniently doesn't mention the combined or city number. People believe that the car will get the highway number when for most drivers and conditions it just won't. The original post states that the 30 MPG they are getting is worse than the regular gasoline powered Camry. Not true!!!! The HIGHWAY mileage, per EPA, is 31. The real story is 21/31. Driving a gasoline camry and a hybrid camry in the same conditions will always show that the hybrid is doing better, IMHO. We (and the car companies) need to set the right expectations. Sure we all know you can do much, much better than EPA with a little work, but the hard fact is that most people just don't (or won't) drive that way.

  7. caplanjr

    caplanjr New Member

    Dan and John,
    Thanks for the great info. John, you're an inspiration -- if I can get close to that mpg, I will be very pleased. Here's some additional info:
    I only drive the car on weekends. Wife takes it for her 9 mile commute during the week while I take the METRO. So, discount the short trip possibility, I didn't include her mileage in my results.

    Can we go back to the idea of pulsing the AC? I haven't looked into the engineering specs on the AC, but unless it's a solid state device, it cools by compressing gas into a liquid and then allowing it to convert back. In the good old days, it was very bad to turn off a compressor and then turn it back on again in less than 2 minutes. In fact, some had timers on them to prevent that. What's the story on the Camry? Any restrictions?

  8. Dan

    Dan KiloTanked in post 153451

    Ok... here's the [post="28673"]tech stuff[/post] that talks about the stages of Toyota operation during warm up. I have a 13 mile commute and most of the time I haven't completed warm-up (S4 transition) when I arrive, so you are definitely in the "too short" commute category. Now the good news is that the Camry does warm up A LOT faster than my car so you will probably hit 70c before you hit 9 miles. So remember to [post="28673"]Force S4[/post], this is required to complete the warm-up cycle and to transition the HSD drive train into "fully enabled".

    Now as for the AC, there are 5 modes:
    1. Heater on, with defrost - I don't think you can get an AS in this mode - HSD is NOT fully enabled.
    2. Heater on without defrost - I think you can get an AS in this mode but it's been so long since I've run heat in my car, I don't recall.
    3. AC on in "Standard" mode - You can get an AS in this mode but the battery charge has to be ridiculously high.
    4. AC on in ECO-AC mode - I don't think you can AS in this mode and is probably the problem. You may get AS functionality if your fully stopped.
    5. AC off - Once you transition to S4, AS happens in a predictable manner without much exception.

    Looking at the list mode 1 and 3 will only let the engine turn off when your stopped. Mode 5 will allow your engine to turn off any time you decelerate and have no pressure on the gas pedal. So in essence you have two problems 1) You may not be forcing S4 which is required to AS on low speed decelerations; 2) Your AC may veto many attempts that the ECU has made to AS the engine.

    Basically the more the engine runs the more gas you burn. The less it runs, the less gas you burn. So the name of the game is to make sure that your car is always in a state that will allow an AS request to be processed. If your battery gets too low, if the AC is on, or if your not in S4, AS requests will often get vetoed.

    So to summarize, AC is a problem, not because of the load it puts on the engine, but because of how it effects the ECUs decisions to AS the engine. Since the AC draws so much power and runs off the traction battery, a 1 minute light is enough to drop your battery charge below the level of allowable AS.

    [post="114728"]Here's my notes[/post] on a review of the TCH I've been working on. It will cover much of the gritty detail on how to get good numbers. For How to Pulse the AC, simply look on your steering wheel. You should see the "AUTO/AC" button. Press it once for on, and once for off. To pulse and glide with the AC (not recommended) here's how:
    1. Accelerate up to (but NOT over) 40 mph. Keep your throttle at 30%. This is called a pulse.
    2. As you approach 38 mph turn off the AC
    3. Take your foot completely off the gas at 40 mph to start a deceleration.
    4. Watch the MPG needle to see it go BEYOND 60 to signal AS
    5. Once you've archived AS shift the car into Neutral
    6. Once your speed is below 38 mph and the car is in Neutral turn on the AC - Your now in a free (no gas, no regen, no engine braking) deceleration. This is called a glide.
    7. Engine will stay off and if your *VERY* light on the accelerator you can shift to D and tool around in EV
    8. Once your ready to acclerate again, put the car back in D and mash the gas, the engine will light and you'll be on your way.

    Pulse and glide should net you between 45 and 65 mpg. The AC will drop your battery fast in the glides and you'll get some back in the pulses, but it usually trends negative. Eventually your battery will get below the threshold and AS will be disabled so the engine can focus on charging the battery. While this is happening you'll only manage about 20-25 mpg. That's why I don't recommend heavy use of the AC. Only way I really recommend it is set to AUTO with the temp dialed in at 85 degF. If this causes the AC to run use it as described above. The thermo at 85 will prevent the compressor from over-taxing the battery. If 85 turns on the heater instead of the AC, then just roll down the windows. Setting the AC to ON-FULL or AUTO 65 will drain a pack in no time flat.

    For cold days, I bring a coat and gloves ;).

    DISCLAIMER: don't worry about phrases like "drain a pack" or "kill your SoC". Your battery is smart enough to prevent you from mucking with it when it charge changes outside it's comfort zone. There is lots of "spare" room worked in to keep the battery from really getting hurt.

    Last edited: Aug 7, 2008
  9. caplanjr

    caplanjr New Member


    Had a chance this weekend to test the accessory load hypothesis. In short, YES, turning off the AC has a dramatic affect on FE. After the engine warmed, I had several 15 minute + trips in the middle 50's and one at 62mpg! And this was suburban stop-and-go driving. Toyota ought to put a warning label on the AC button <grin>.

    Friday we go to the dealer to check the oil overfill hypothesis. I also want to find out why the stack discharges so quickly, even w/o the AC. Anyone have additional suggestions to have checked while I'm there? And one other question, is there an online video demonstrating P&G? I'd like to verify that I'm doing it right.

    Thanks for all the help,
  10. I hit 40mpg on the way home from the dealer, an approximately 70-mile drive from the Denver area to the Colorado Springs area. I took a back road with rolling hills instead of I-25 and its 75mph speed limit. Still, the trip was generally uphill from about 5000ft in Denver to about 7000ft at my house. I didn't drop below 40mpg until winter.

    I've read (can't remember where) that 10 miles is the point where you start seeing a significant advantage from the HSD. I've definitely noticed that short trips kill fuel economy. My TCH tends to stay warmed up (or get back to a warmed-up state very quickly) if it remains parked for less than 1-2 hours, even in winter, so grouping errands with the longest one first is definitely beneficial. The worst combo is a short trip starting with a low state of charge.

    In the summer, my TCH is typically ready to do an AS at the traffic light about 1.5 miles from my house. In the winter, it's typically ready at the next light about 1.5 miles further down the road.

    My experience with the climate control over the past few months is a bit different from what you describe. I don't know what could account for these differences. Mine is an early 08 TCH (purchased September 20-something 2008).

    Colorado is fairly dry, so I seldom run the defroster. I do typically run the heater in winter, and have had no trouble getting the car to AS, once it's warmed up.

    I never run in AC "standard" mode, but I have lately been running AC in ECO mode. I only noticed one instance where the car didn't AS with AC on, but immediately shut off when I turned the AC off. However, I had just pulled out of a parking lot and was maybe 0.5 miles into the trip at that time. I frequently see the engine shut off in this configuration, though it's much harder to maintain a good state of charge.

    I don't have a ScanGauge, so I can't confirm stage transitions. I recently did an AC vs. no AC experiment, and didn't notice a significant difference in any aspect of the car's behavior, except a ~2mpg (5%) fuel economy penalty and more difficulty maintaining charge with AC on.

  11. jmonti

    jmonti Member

    I think 10 miles (maybe less) is about the general "break even point" depending on lots of external factors. In summer I often have a cold car get into S4 within the first 3-4 miles. Now, of course, you need to continue to drive to get that benefit of being in S4.

    I've also been very pleased with how "warmed up" the car stays. Planning errends from longest trip first is definately the way to go.

    I have a light about 2.5 miles into my commute. The first 2 miles is 45 MPH and the last 0.5 is 40 MPH. When I slow to below 40 I often will drop into EV (S3 - though no stop which seems strange to me). Then at the light, I can often (not always) refire the ICE and get S4 (sometimes ICE goes off fast and I stay in S3 until the next light - another mile).

    When I use the A/C (which is rare - usually on long trips with my wife in the car :) ) I always have ECO ON. On the rare occation when I use it around town, I have noticed some cases where the ICE won't go off when it normally would. Its not always though I don't have enough data to really tell what's going on.


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