Reason MPG readout is wrong?

[toybox]

I got to thinking after a few threads I read, since the readout says that when you have 0 miles DTE it still has about two gallons left in the tank. So if it uses 23 gallons in one part of its' equation (true capacity) and only 21 gallons in another part of the equation (computers capacity) that may be the cause of the 10 to 15% difference in actual MPG compared to the readout MPG.

Am I thinking too much or could there be a link between the two causing the difference?:bonk:

 

[boston_kevin]

works for me... I think they put in the range (DTE) as a function of 21 gallons so you wouldn't risk damaging the fuel pump in the tank. More than likely someone else programmed 23 gals since that's the official tank capacity... The question is, what about these guys with the 24.5 galllon tanks? (see a previous thread)

 

[mjfrank]

I think the MPG readout calculation is based on the number of injector pulses per mile. (or some fraction therein) The amount of gas in the tank has no bearing on it. It does use the MPG data with the fuel level to calculate DTE though.

--Mike

 

[toybox]

works for me... I think they put in the range (DTE) as a function of 21 gallons so you wouldn't risk damaging the fuel pump in the tank. More than likely someone else programmed 23 gals since that's the official tank capacity... The question is, what about these guys with the 24.5 galllon tanks? (see a previous thread)

If this is actually what is happening it seems like it would be an easy fix for Toyota.

And now that you mention the people who fill their fill tube up with an extra 1.5 gallons, it would be a good way to possibly verify this theory if they could tell us the difference between their actual and readout mileage.

 

[Koz]

toybox,

Yes, you are thinking too much! :bonk:

Koz

 

[toybox]

toybox,

Yes, you are thinking too much! :bonk:

Koz

:beer: I need to stop thinkin' and start drinkin' :arrow:

 

[Iowa4Runner]

I got to thinking after a few threads I read, since the readout says that when you have 0 miles DTE it still has about two gallons left in the tank. So if it uses 23 gallons in one part of its' equation (true capacity) and only 21 gallons in another part of the equation (computers capacity) that may be the cause of the 10 to 15% difference in actual MPG compared to the readout MPG.

Am I thinking too much or could there be a link between the two causing the difference?:bonk:

Well... Having a 4Runner with an accurate MPG readout, I can tell you the DTE is still off by a couple gallons at 0. Until the fuel level sensor and/or computer get recalibrated to learn the true empty point of the tank, the DTE will always be off as you approach empty.

My understanding is that the MPG is calculated by monitoring the injector pulses and odometer, while the DTE is derived from the fuel tank level and the recent MPG average. If this is the case then MPG would have an effect on DTE but not vise versa. But again, without a good zero point, the DTE can never be hope to be accurate across a range of values regardless of how good the MPG info is.

 

[Northof49]

I've also had mine to "0" a few times......I'm kinda glad "0" wasn't really 0 hahaha

I guess they calibrate it that way so that the Kramer's of the world won't be running out of gas trying to run it empty hehe

 

[toybox]

Re: Re: Reason MPG readout is wrong?

Well... Having a 4Runner with an accurate MPG readout, I can tell you the DTE is still off by a couple gallons at 0.

Are you saying that your mpg readout is correct and accurate?

If that is the case then I am very confused. I thought they were ALL off about 10%. Oh well, I just shut that part of the readout off last night so that I stop thinking about it. I'm just gonna:driving:

 

[00void]

:beer:

that thing rules! hahaha

 

[Iowa4Runner]

Re: Re: Re: Reason MPG readout is wrong?

Are you saying that your mpg readout is correct and accurate?

If that is the case then I am very confused. I thought they were ALL off about 10%. Oh well, I just shut that part of the readout off last night so that I stop thinking about it. I'm just gonna:driving:

I made a modification to my 4Runner

Check out:

http://www.toyota-4runner.org/showthread.php?s=&threadid=5635&highlight=MPG+adjuster

 

[Kmvreter]

I made a modification to my 4Runner

Check out:

http://www.toyota-4runner.org/showthread.php?s=&threadid=5635&highlight=MPG+adjuster

That thread isn't updated. How accurate are you? Did this mod work?

 

[Iowa4Runner]

Re: Re: Reason MPG readout is wrong?

That thread isn't updated. How accurate are you? Did this mod work?

Oh yes it certainly works. I check it at every fillup, and it's usually less than 1% off. The average error over the last ten tankfulls was 0.84%.