RX350

What is it with the fuel guage and the distance remaining display. It
seems to declare a shorter distance remaining than there is in reality.
All this assuming the declared fuel capacity is correct. Is there a
reserve fudge factor put in?

John

"The Visitor" <ksjhdsdfssjhfk (AT) shduiysdfsrewh (DOT) com> wrote

What is it with the fuel guage and the distance remaining display. It
seems to declare a shorter distance remaining than there is in reality.
All this assuming the declared fuel capacity is correct. Is there a
reserve fudge factor put in?

John

I would think that it is safer to under-estimate remaining distance than
over-estimate and leave you stranded. Running the vehicle out of fuel will
eventually ruin the fuel pump and can damage the catalytic converter.
--

Ray O
(correct punctuation to reply)

Ray O wrote:

I would think that it is safer to under-estimate remaining distance than
over-estimate and leave you stranded. Running the vehicle out of fuel will
eventually ruin the fuel pump and can damage the catalytic converter.

Well yes that is what it is doing. if I didn't have that number there i
would drive it down to 1/8 of a tank in town. But going by that number,
I have to fill up at the 1/4 mark and it is a bit bothersome. I dislike
hidden or built in reserves because you start to ignore things over time.

"The Visitor" <ksjhdsdfssjhfk (AT) shduiysdfsrewh (DOT) com> wrote

Ray O wrote:

I would think that it is safer to under-estimate remaining distance than
over-estimate and leave you stranded. Running the vehicle out of fuel
will eventually ruin the fuel pump and can damage the catalytic
converter.

Well yes that is what it is doing. if I didn't have that number there i
would drive it down to 1/8 of a tank in town. But going by that number, I
have to fill up at the 1/4 mark and it is a bit bothersome. I dislike
hidden or built in reserves because you start to ignore things over time.

If you do not mind risking damage to your fuel pump and catalytic converter
by running the fuel tank low or empty, it is possible to increase the
distance indicated in the distance-to-empty display.
--

Ray O
(correct punctuation to reply)

Ray O wrote:

If you do not mind risking damage to your fuel pump and catalytic converter
by running the fuel tank low or empty, it is possible to increase the
distance indicated in the distance-to-empty display.

It seems to underestimate by quite a bit. Is this adjusted at the
dealership with their plug in 'thingy'? Or can I do it? I have never ran
a tank dry yet. But having this thing scare me into filling it up at the
1/4 mark is a bit much. Bkut if I could bring myself to not look at it,
then I I would run it down to the 1/8 mark. Not a big deal around here.

I have not had one of these discance remaining displays before. Sure
nobody wants it to overestimate, but to so grossly underestimate only
causes it to be ignored.

John

"The Visitor" <ksjhdsdfssjhfk (AT) shduiysdfsrewh (DOT) com> wrote

What is it with the fuel guage and the distance remaining display. It
seems to declare a shorter distance remaining than there is in
reality.
All this assuming the declared fuel capacity is correct. Is there a
reserve fudge factor put in?

I made this same observation two years ago about my 2004 ES330. See:

http://groups.google.com/group/alt.a...thread/ed89065
1cecb106a/d248d59cfc7e8d58?tvc=1&q=lexus+gas+gauge+david#d24 8d59cfc7e8d5
8

David Z wrote:

I made this same observation two years ago about my 2004 ES330. See:

http://groups.google.com/group/alt.a...thread/ed89065
1cecb106a/d248d59cfc7e8d58?tvc=1&q=lexus+gas+gauge+david#d24 8d59cfc7e8d5
8

So nobody really knew.

With my last car, an Audi, 1/4 was actually 1/4 of the tank.

If I fill up at 1/4 mark now, it takes 75 % of the stated capacity. Fine.

But the distance to empty number says something like 75 km. (I'm i
Canada) but based on my mileage, I should be able to to 135 km to empty.

If it were not for the distance to empty, I would happily run it down to
1/8 of a tank in town. But that number, Grrrrr, scares me into untimely
fill-ups.

Or is the stated capacity of the tank wrong?

John

"The Visitor" <ksjhdsdfssjhfk (AT) shduiysdfsrewh (DOT) com> wrote

I made this same observation two years ago about my 2004 ES330.
See:


http://groups.google.com/group/alt.a...thread/ed89065

1cecb106a/d248d59cfc7e8d58?tvc=1&q=lexus+gas+gauge+david#d24 8d59cfc7e8d5
8

So nobody really knew.

With my last car, an Audi, 1/4 was actually 1/4 of the tank.

If I fill up at 1/4 mark now, it takes 75 % of the stated capacity.
Fine.

But the distance to empty number says something like 75 km. (I'm i
Canada) but based on my mileage, I should be able to to 135 km to
empty.

If it were not for the distance to empty, I would happily run it down
to
1/8 of a tank in town. But that number, Grrrrr, scares me into
untimely
fill-ups.

Or is the stated capacity of the tank wrong?

One way to figure it out is to fill your tank and set your trip odometer
to zero. Then observe how many miles the range gauge counts down for
each 10 miles of driving. If the trip gauge counts down linearly for
the whole tank of gas, then it's probably not the cause of the
distortion. If it's not linear, then Lexus/Toyota has deliberately
skewed the range gauge so that people don't run the tank down too low.

Having just thought of it, I may try this idea myself sometime. The
problem is if your driving is not consistently highway, street or a
consistent mix of the two, your measurements will be distorted,
accordingly. Also, we don't know how the range gauge is programmed.
For example, does it assume a 50/50 ratio of highway/street driving or
what?

"David Z" <me (AT) privacy (DOT) net> wrote

"The Visitor" <ksjhdsdfssjhfk (AT) shduiysdfsrewh (DOT) com> wrote in message
news:hRN5h.839$J32.360 (AT) read1 (DOT) cgocable.net...

I made this same observation two years ago about my 2004 ES330.
See:


http://groups.google.com/group/alt.a...thread/ed89065

1cecb106a/d248d59cfc7e8d58?tvc=1&q=lexus+gas+gauge+david#d24 8d59cfc7e8d5
8

So nobody really knew.

With my last car, an Audi, 1/4 was actually 1/4 of the tank.

If I fill up at 1/4 mark now, it takes 75 % of the stated capacity.
Fine.

But the distance to empty number says something like 75 km. (I'm i
Canada) but based on my mileage, I should be able to to 135 km to
empty.

If it were not for the distance to empty, I would happily run it down
to
1/8 of a tank in town. But that number, Grrrrr, scares me into
untimely
fill-ups.

Or is the stated capacity of the tank wrong?

One way to figure it out is to fill your tank and set your trip odometer
to zero. Then observe how many miles the range gauge counts down for
each 10 miles of driving. If the trip gauge counts down linearly for
the whole tank of gas, then it's probably not the cause of the
distortion. If it's not linear, then Lexus/Toyota has deliberately
skewed the range gauge so that people don't run the tank down too low.

The gauge will not move down in a linear fashion because the float for the
gauge moves in an arc like the float in a toilet tank, and the tank has an
irregular shape. The primary goal of the fuel tank's design is to fit in a
particular space and to be crash-worthy. Shaping the tank so the gauge
would move in a linear fashion would reduce the tank's capacity and the
vehicle's range.

Having just thought of it, I may try this idea myself sometime. The
problem is if your driving is not consistently highway, street or a
consistent mix of the two, your measurements will be distorted,
accordingly. Also, we don't know how the range gauge is programmed.
For example, does it assume a 50/50 ratio of highway/street driving or
what?

I believe that the MPG display is derived by calculating distance traveled

and dividing it by an estimate of how much fuel was consumed, either from
injector pulse duration or from a flow meter in the fuel system. With the
same amount of fuel in the tank, a driver with a light foot will get better
MPG than a driver with a heavy foot or who is driving in stop-and-go
traffic. The system then uses MPG to calculate distance to empty. You can
increase the distance-to-empty reading at any time by driving at a steadier
speed than you were just before.
--

Ray O
(correct punctuation to reply)

"Ray O" <rokigawaATtristarassociatesDOTcom> wrote

The gauge will not move down in a linear fashion because the float for
the
gauge moves in an arc like the float in a toilet tank, and the tank
has an
irregular shape. The primary goal of the fuel tank's design is to fit
in a
particular space and to be crash-worthy. Shaping the tank so the
gauge
would move in a linear fashion would reduce the tank's capacity and
the
vehicle's range.

Are you talking about the gas gauge or the range gauge here, or both?

Shouldn't both gauges be calibrated to account for the shape of the
tank?