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trader_4 trader_4 is offline
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Default What is the realistic accuracy & precision of typical consumerMPG calculations (tripmeter miles/pump gallons)

On Sunday, July 23, 2017 at 7:20:18 AM UTC-4, Vic Smith wrote:
On Sat, 22 Jul 2017 21:10:41 -0400, wrote:

On Sat, 22 Jul 2017 23:42:25 -0000 (UTC), Mad Roger
wrote:

On Sat, 22 Jul 2017 00:46:50 -0400,
rickman wrote:

So my odometer is accurate and precise.

I understand you because you're exactly the type of person that I had in
mind when I asked the question in the first place.

I don't know what you mean. I have checked my odometer against the markers
on the highway as well as against my GPS (I think the highway markers are
more accurate than the GPS). It is spot on with the current tires to 1% or
better.

Does your tripmeter have a decimal place and digits after that decimal
place?

snip

Which is the entire point after all.

The man is right You are wrong. You ASS U ME too much - and at the
risk of insulting the few GOOD engineers on the list, you OBVIOUISLY
are an "engineer", but not one I'd hire for a job. The job would come
in WAY over budget, WAY late, and would need to be completely redone
by techitians and technologists at great cost, or to save time and
money, completely decommissioned and scrapped - starting over with
someone who knew what thet were doing, and how to do it - engineer or
not.


You know, this guy has a hard-on against "non-engineers" measuring their MPG.
Rickman above told him he uses his odometer, then he goes on about tripmeters.
I answered his main complaints in another post. That exchange went like this:

"+ Tripmeter accuracy is what in the average car over a 300-mile tank?
+ Owners ability to "match" the previous level of fuel is what?
+ Gas station pump reading accuracy is what?


I never used the tripmeter for MPG, because I never bothered testing them with mile
markers.
Matching gas level is trivial - and it only has to done at the beginning and end of the
trip.
Gas station pumps - I assume they are accurate, and can't control that anyway.
I'm confident that my measurements are accurate to within .1 MPG."

His response to me totally ignored those responses, and he posed the same questions again!
Then, for some reason, he stated talking about speedometers.
He's a troll.


I noted the same thing in his other thread about wheel sizes. Right from
the start Mad Roger made the wrong assumption that torque at the wheel
translated directly into fuel usage. He was conflating torque with
work/energy. So, I carefully explained it, gave him examples of lifting
a 100lb rock up 2ft using a 4 ft lever or a 10 ft lever. While the
torque is different, the work/energy used is exactly the same. Gave
him another example of a bicycle going uphill with different gear ratios.
Did he acknowledge that, discuss it? No, just like with your example,
instead he obfuscated by then bringing up wind resistance and continued
to troll on. He also claimed to be a "scientist", then he says that
DPB's post about fuel pump accuracy was confusing because he used
cubic inches and gallons?

We don't agree on a lot things, but we sure agree on this!