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  #1  
Old 07-03-2011, 11:25 PM
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Question About DTE?

How accurate is the DTE in the EVIC? Today I drove 140 miles round trip all highway, I filled up the tank before I started and during my trip I got between 22-24.5 mpg on the EVIC display at 65-70 mph, but the DTE never went above 380 miles to empty. When I started my trip the DTE displayed 375 after the fill up and at the end of the trip the DTE displayed 339 after driving 140 miles. If I averaged 23mpg and had a full tank at 24.5 gallons. Should the DTE display read around 563 miles to empty or close to that during the trip?
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Old 07-04-2011, 05:00 AM
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Re: Question About DTE?

How many miles on your odometer? If still in the break-in phase I wouldn't believe the DTE will be accurate. Otherwise it should be correct within reason. I still prefer the hand-calc method to give me a range estimate.




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Old 07-04-2011, 05:33 AM
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Re: Question About DTE?

Most DTE systems work of the average fuel consumption of the car since the average fuel consumption was reset, or since its first tank. This is why careful driving will not result in a being change unless you reset the fuel computer.
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Old 07-04-2011, 07:48 AM
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Re: Question About DTE?

Reset the average MPG when you fill the tank and it should adapt as you drive. I get a kick out of seeing it increase the miles till empty. We joke about it adding fuel as we drive making it the super hybrid
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Old 07-04-2011, 09:36 AM
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Re: Question About DTE?

The thing is , I did reset the mpg when I filled up and twice during the trip in hopes the DTE would correct itself. I also do the gallons put in versus the miles driven calculation when I fill up and the computer is always off by 1-3 miles per gallon. For example on my last fill up, the EVIC computer showed 15.9 mpg but my calculatoins gave me 13.8 mpg. Just wondering if my computer is just off. I never seem to get anywhere closse to what the computer shows. I currenty have 2450 miles on the OD, so maybe once the this thing is a little more broken in, the read out will be more accurate!
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Old 07-04-2011, 09:48 AM
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Re: Question About DTE?

Quote:
Originally Posted by NHman View Post
How many miles on your odometer? If still in the break-in phase I wouldn't believe the DTE will be accurate. Otherwise it should be correct within reason. I still prefer the hand-calc method to give me a range estimate.

Regards,
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What is the break in period?
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Old 07-05-2011, 09:36 AM
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Re: Question About DTE?

Quote:
Originally Posted by fljeepleo View Post
What is the break in period?
Strictly speaking, about 500-1000 miles, but in practice, the engine isn't fully "settled in" until about 5000 miles or so. I noticed my own fuel efficiency getting rather better as I got close to 10,000 miles.

The DTE is a pretty general help; IMO, it's best used for "if I don't stop here and get screwed for another 50 cents/gallon but keep going for 30 miles, can I make it?" There's just no way to know that even your average fuel consumption can be predicted with true certainty. Personally, I start thinking about fuel when I get to 1/4 left.
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Old 07-05-2011, 03:50 PM
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Re: Question About DTE?

Displayed mileage is probably computed using a weighted moving average. This factors in mileage over a period but assumes that recent mileage is more important in predicting future performance. Unless you know the formula, your own calculations won't match.

DTE will never be better than a ballpark estimate. You're literally asking the car to predict the future. All it can do is take its best guess and keep that updated.
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Old 07-05-2011, 03:53 PM
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Re: Question About DTE?

Quote:
Originally Posted by plynn7 View Post
The thing is , I did reset the mpg when I filled up and twice during the trip in hopes the DTE would correct itself. I also do the gallons put in versus the miles driven calculation when I fill up and the computer is always off by 1-3 miles per gallon. For example on my last fill up, the EVIC computer showed 15.9 mpg but my calculatoins gave me 13.8 mpg. Just wondering if my computer is just off. I never seem to get anywhere closse to what the computer shows. I currenty have 2450 miles on the OD, so maybe once the this thing is a little more broken in, the read out will be more accurate!

Do you sit at idle a lot?
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Old 07-05-2011, 05:51 PM
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Re: Question About DTE?

Quote:
Originally Posted by Andrew Klossner View Post
Displayed mileage is probably computed using a weighted moving average. This factors in mileage over a period but assumes that recent mileage is more important in predicting future performance. Unless you know the formula, your own calculations won't match.

DTE will never be better than a ballpark estimate. You're literally asking the car to predict the future. All it can do is take its best guess and keep that updated.
Shouldn't the computer give you an estimate as your driving conditions change? So if I maintain 60 mph for a given time, the DTE should recalculate and show what the DTE would be if I continue to drive at that speed, letís say after 10 miles or so. Also I am not looking for dead on accuracy just a close estimate, and I can't seem to acheive that. Whatís the point of this system if it does not adjust to your driving changes in a timely manner? After driving 140 miles all highway on a full tank at 60-65 mph the DTE never went above 380.
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Old 07-05-2011, 06:12 PM
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Re: Question About DTE?

Quote:
When I started my trip the DTE displayed 375 after the fill up and at the end of the trip the DTE displayed 339 after driving 140 miles.
But it did change. It only dropped 36 miles when you actually drove 140. (or add 140 + 339 = 479 for total tank, there is just less fuel in the tank now).

Jeep has ~24 gallon tank, at 23 mpg = 552 - 140 (that you drove) = 412. Subtract another 46 (2 gallon fuel reserve) = 366. So (366-339)/366 = ~8% error. Not bad considering the mpg range of the car (16 to 23). Or think this way, gas mileage can change the range by up to 30% at rated mpg.

The problem is that you "reset" it; than tried the test. My BMW was always really inaccurate after a reset, but would do great after forgetting about it for 6-8 months. The 1st few minutes after a reset (how you drive) greatly affects these formulas from my experience. So if you sat and idled for 2 minutes at a shop light, right after reset prior to getting on the highway your results would be hugely affected as the computer only has 2 minutes of data at 0 mpg. You can see this by doing several resets in a row while driving down a road (you mpg will go all over the place versus nicely adjusting up/down based on city/hwy driving). I think there was a thread on here where people had fun show everything from 0 to 99 mpg based on when the pressed reset.
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Old 07-05-2011, 08:41 PM
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Re: Question About DTE?

I can appreciate how the calculations work, I can to do that, but I am wondering why after driving 10, 20, 30 miles at the same speed without stopping the DTE should not remain static When I started it was a full tank and mpg displayed was 15.9 and increased to an average of 23 mpg but the DTE never increased, it should increase, unless my driving habit changes. Why can’t the computer adjust to show the estimated distance to empty? I should not have to do calculation on the fly, that’s what the computer is supposed to be for. This is not a big deal; I never go below a ľ tank, just nice to have a little more accuracy or a quicker response from the DTE read out.
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