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A bloke from a green group said most cars don't get better than 40% of what they claim under current testing regime.
The woman from the EU department creating the new test regimes said they will get within 15 - 20% under new regimes incoming. When asked why not closer than that, she said because driving styles differ, local driving conditions differ, etc.
Apparently the current regime (about to be superseded) doesn't allow for the fact that you might drive up a hill! "Real-world", eh?
Presumably most people who drive up a hill then drive back down, so it doesn't make a vast difference.
Wind speed and direction makes a big difference too - the overriding factor in fuel use when you're cruising at motorway speed is air resistance, so if you're driving into a 10mph headwind, that's the same in fuel terms as driving 10mph faster. You don't get all that back if it's a tailwind either - since air resistance is proportional to the square of the speed, an increase hits you more than you gain from a decrease of the same amount.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
I understand, of course, that going up hill uses more fuel, but I also understand that accelerating uses more fuel, and conflating the two doesn't give a fair picture. In the real world (which is the sort of testing we were talking about) most people slow down a bit going up a hill, and speed up a bit on the way down - which is the opposite of what you're claiming.
If you maintain a steady speed then - frictional losses aside - you only need to burn enough extra fuel to balance the gain in gravitational potential energy - and you get that back on the way down. The frictional losses are going to be pretty much the same no matter the gradient.
And you you still use more fuel due to the "acceleration".
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
When going up hill you have to fight gravity. Well a proportion of it anyway (the amount depended on the gradient) This will be a force acting backwards.
To maintain an equal speed to have to apply a forward force of the same about. So you have to accelerate at the same amount as you are being de-accelerated.
good argument, well presented...
I'm not locked in here with you, you are locked in here with me.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
I'm not locked in here with you, you are locked in here with me.
It is a product of the changing forces being applied. Therefore if speed is constant acceleration equals zero. It is the force that is changing to compensate for the work being done to overcome the effect of gravity.