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Old 12-26-2012, 10:00 PM   #11 (permalink)
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Very often I find that different pumps will fill up my tank to different levels. If I calculate my mpg manually and come up with a low mpg average, on average the very next time I calculate at fill up it will come up high. If I divide the two it comes up to what my fcd shows. Trust the fcd!

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Old 12-26-2012, 11:12 PM   #12 (permalink)
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Quote:
Originally Posted by Need4Speed View Post
My gas calculations are usually very close to what the display shows. Typically the display is less than 2% off from what I calculate. My calculations are typically a little lower than the fcd, but sometimes the fcd is slightly lower. I have also read that temperature affects the actual amount of gas, that the pumps are calculated at a given temp (72?). I believe I read an article that people in Canada have complained that ov a year time frame the average temp is less than the cal temp, so in the long run they are getting jipped. People in warm states might be getting more than they are paying for.
If I remember correctly about the USA pumps, the oil companies said it would cost too much to put the temperature compensated pumps in.

Except in Hawaii, where I think the state demanded they put them in and it wasn't too much to do.
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Old 12-28-2012, 03:14 AM   #13 (permalink)
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On average, the FCD is accurate to within 1%. But it can swing as much as like 8%.

For me, at least.
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Old 03-21-2013, 12:37 AM   #14 (permalink)
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I just re-fueled. The FCD showed 58.9mpg, but my calculation showed 55.4 (for almost an entire tank)
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Old 03-27-2013, 09:37 AM   #15 (permalink)
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Just did my first full tank in the car: display showed 57.1, fillup calculation added up to 57.0958.
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Old 03-27-2013, 10:35 AM   #16 (permalink)
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I've tracked the FCD in my HCH1 over 21000 miles now (every fill up, actual mpg and the displayed FCD recorded).

The result: The FCD is actual MPG + 1.99.

I also tracked my I1 the same way over 36000 miles.

The FCD was actual mileage + 1.08.

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Old 05-31-2013, 01:10 PM   #17 (permalink)
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Quote:
Originally Posted by olrowdy01 View Post
If I remember correctly about the USA pumps, the oil companies said it would cost too much to put the temperature compensated pumps in.

Except in Hawaii, where I think the state demanded they put them in and it wasn't too much to do.

This seems so ironic since Hawaii has the smallest temperature variation of any place in the states. In the 14 months I lived there I don't remember it ever being over 90, usually not over 85. And it seemed like a cold snap when it got down below 70 at night and I had to shut the windows to stay warm. Where buildings typically don't have AC or heat, demanding temperature compensated pumps seems foolish.
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Old 05-31-2013, 02:07 PM   #18 (permalink)
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Default Cold vs warm gas

Gasoline expands when it warm and there are less molecules per volume than if the fuel was cooler. Therefore cold states/Canada get more energy per gallon of fuel by volume (the pumps dispense fuel by volume) than warm states if the pump isn't temperature compensated.

At the same time the station storage tanks are typically underground and the temperature is more stable underground (which is normally the average temperature of the location). Admittedly the storage tanks are usually under the pavement at the station and that might increase the temperature at the tank in sunny, warm states.
---

Honda emissions canisters are usually pretty small and I can't imagine that the Insight canister and it's hoses can hold ~3 gallons of fuel. Typically the canister is higher than the top of the fuel tank so liquid fuel shouldn't get into it.

[After studying the blow up drawings of the Insight fuel system.]
There is also a "two way valve" which allows air to enter the tank as fuel is used up but builds up a little pressure in the tank before it releases air (or perhaps fuel) into the canister. The ECM tests for that pressure and will throw a MIL if the air pressure doesn't exist (for instance if you don't tighten the gas cap properly).

But there might be enough fuel separator volume in the gas tank to hold a gallon or so if you put the fuel in slow enough. It would depend upon how far the air vent tube from the filler pipe extends down into the fuel tank (which creates the separator area), if the car is level etc.

In a good fuel system design the two way valve would be attached to the very top of the fuel separator volume so under a normal filling session no liquid fuel should be able to get to the canister. If nothing else the air pressure in the fuel separator won't be high enough to pass through the two way valve.

I usually fill my cars by slowing the fuel flow down when the tank is within a gallon or so of where the nozzle is going to kick off. Then I even the $$.xx up to some amount and stop. I also try to go to the same station/pump if possible.
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Old 05-31-2013, 02:17 PM   #19 (permalink)
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Quote:
Originally Posted by weelliott View Post
This seems so ironic since Hawaii has the smallest temperature variation of any place in the states. In the 14 months I lived there I don't remember it ever being over 90, usually not over 85. And it seemed like a cold snap when it got down below 70 at night and I had to shut the windows to stay warm. Where buildings typically don't have AC or heat, demanding temperature compensated pumps seems foolish.
[conspiracy theory] I wouldn't doubt that the gas companies didn't mind doing it because they could then claim that the new pumps didn't save people money. [/conspiracy theory]

Especially so when you see this,

The table below displays the average monthly temperature in Honolulu Hawaii.

Temperature by: Fahrenheit
Honolulu Temperature Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
Avg. Temperature 72.9 73.0 74.4 75.8 77.5 79.4 80.5 81.4 81.0 79.6 77.2 74.1 77.2

The average year round temperature is only 5 above the pump certification temperature.
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Old 05-31-2013, 02:40 PM   #20 (permalink)
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Right on roydy1.
Here in my town, the temps. can vary as much as 40 degrees between day and night.
http://www.weather.com/weather/wxcli.../monthly/91906
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