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Old 02-10-2011, 05:51 PM   #1 (permalink)
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Default Disconnect Between iMPG and avg mpg meters

While trying to compare my mileage without CC vs with, I noted the following with CC off and watching the MID on trip B instantaneous and avg mpg meter. With 20 miles on the meter, the avg mpg was 46.4 mpg, and I was holding the instantaneous meter at 50 mpg. So, I'm expecting to see the avg start ticking up toward 50 mpg. After a few seconds, the avg dropped to 46.3. Odd, I thought. Another minute or so, instantaneous steady as a rock at 50, avg drops to 46.2. I swear I held the instantaneous at 50 while watching the average fall to 45.9 before I finally let instantaneous slip from 50. I can't explain this.

Has anyone else noticed something like this? Does anyone have an explanation?
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Old 02-12-2011, 09:18 AM   #2 (permalink)
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Two days and no replies, so I guess no one else has ever had this happen?
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Old 02-12-2011, 08:49 PM   #3 (permalink)
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I feel it's just a guide. Not really what you're getting for mileage. I did not reset the trip mileage this last tank and am not getting those wild mileage swings for the first few gallons like I do on a reset. I hold mine for extended times at 50 but can't seem to get over 43.9 this winter. looking forward to warmer weather for a mileage increase. No CC on my model. Were you going up a imperceptable grade at the time.(blue screen?)

Last edited by freddy the mug; 02-12-2011 at 08:55 PM.
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Old 02-13-2011, 09:30 AM   #4 (permalink)
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Freddy, thanks for the reply. I can't agree that it's just a guide. Gauges and displays should do what they purport to do; in this case, provide instantaneous and average fuel consumption. After a reset you should expect wild swings in your average, until you get several miles on the meter then it should settle down and change slowly. My assumption is if I reset trip B then that resets the average fuel consumption to zero. Then, as I drive the computer will periodically look at fuel consumed and miles on trip B and calculate the average fuel consumption. If this is true, then if I hold the instantaneous consumption constant at a higher value than the current average, then the average should begin to move up toward the higher instantaneous value. It should not matter whether I'm on a grade; I held instantaneous at a constant value, so average should be increasing, not decreasing. If this is incorrect, can someone tell me where I'm wrong. Otherwise I'm going to the dealer.
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Old 02-20-2011, 01:25 AM   #5 (permalink)
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Default Same boat

Actually, I've had exactly the same experience - keeping my instantaneous mileage well over my avg, yet seeing my avg drop.

I'm curious; have you learned anything from the dealer? My guess is that they don't have a lot of detailed knowledge about the car's software, but perhaps I'm wrong.
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Old 02-20-2011, 10:55 AM   #6 (permalink)
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Originally Posted by cdaughton View Post
Actually, I've had exactly the same experience - keeping my instantaneous mileage well over my avg, yet seeing my avg drop.

I'm curious; have you learned anything from the dealer? My guess is that they don't have a lot of detailed knowledge about the car's software, but perhaps I'm wrong.
cdaughton, thanks for the feedback. If its happened to someone else, then perhaps I'm not insane. Well, maybe I'm just a little insane. It hasn't recurred, and for my last 3 fillups the MID has been less than 5% different from calculated, so I'm not as concerned as I was right after I noticed the problem. I say all this to excuse the fact that I haven't gone to the dealer yet. I decided to wait for my first oil change. I'll update this thread when I know what they say, but I suspect you're right about the dealer's knowledge of the software, and this is probably a software issue.
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Old 02-28-2011, 09:46 PM   #7 (permalink)
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Originally Posted by amorris View Post
With 20 miles on the meter, the avg mpg was 46.4 mpg, and I was holding the instantaneous meter at 50 mpg. So, I'm expecting to see the avg start ticking up toward 50 mpg. After a few seconds, the avg dropped to 46.3. Odd, I thought. Another minute or so, instantaneous steady as a rock at 50, avg drops to 46.2. I swear I held the instantaneous at 50 while watching the average fall to 45.9 before I finally let instantaneous slip from 50. I can't explain this.

Has anyone else noticed something like this? Does anyone have an explanation?
I haven't noticed anything like this but it is an interesting question. Some factors to consider in searching for an explanation.

1. My understanding is that instantaneous mpg, with a reading of 50, is 'actually' somewhere between 45 and 50.

2. The average is recomputed every ? period of time. I think its every minute.

3. It could be that prior to the reduction in the average from 46.4 to 45.9 there were periods of very low instantaneous mpg (due to acceleration) and a period of very high instantaneous mpg (battery only EV mode which is reported as 150 average mpg). If so, the initial 46.4 is a false high that reflects the computer software's poor ability to accurately measure mpg while in EV mode. Some additional miles would be needed to average out these extremes of instantaneous mpg.

4. I have repeatedly found that the MID is more optimistic of actual mpg, when the tankful being measured included lots and lots of EV mode driving. I talked with the dealer last year, and sent a complaint to Honda's USA HQ. As far as I know, no software fix has been made.
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Old 02-28-2011, 10:19 PM   #8 (permalink)
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Originally Posted by Moviemike View Post
I haven't noticed anything like this but it is an interesting question. Some factors to consider in searching for an explanation.

1. My understanding is that instantaneous mpg, with a reading of 50, is 'actually' somewhere between 45 and 50.

2. The average is recomputed every ? period of time. I think its every minute.

3. It could be that prior to the reduction in the average from 46.4 to 45.9 there were periods of very low instantaneous mpg (due to acceleration) and a period of very high instantaneous mpg (battery only EV mode which is reported as 150 average mpg). If so, the initial 46.4 is a false high that reflects the computer software's poor ability to accurately measure mpg while in EV mode. Some additional miles would be needed to average out these extremes of instantaneous mpg.

4. I have repeatedly found that the MID is more optimistic of actual mpg, when the tankful being measured included lots and lots of EV mode driving. I talked with the dealer last year, and sent a complaint to Honda's USA HQ. As far as I know, no software fix has been made.
Moviemike, thanks for your input. It seems to me that for an indicator calibrated in increments of 5mpg that a reading of 50 should indicate an actual value from 47.5 to 52.5, but I don't know what the meter actually does. It has occurred to me that if the avg reading is based in part on a predictive algorithm that could explain what happened. But that sounds overly complex. I would love to know how it really works.
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Old 03-01-2011, 06:55 PM   #9 (permalink)
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Default mpg

What is this EV mode I keep reading? Our Insights do not have an EV mode. The electric motor is used for torque and/or acceleration only.
It has engine shut off mode but thats not EV.
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Old 03-02-2011, 08:07 PM   #10 (permalink)
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Freddy, I beg to differ about the EV mode. Page 84 of the manual shows a mode where only the IMA motor is powering the vehicle. If only the electric system is providing power, then that is an EV mode. Granted, it is computer selected; the driver cannot press an EV button, but you can drive in such a way that the computer will select EV. I do it frequently, just to see how long I can make it last.
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