Quote:
Originally Posted by Christ
So here's where I'm confused... you say that a 30mpg vehicle that weights one 1 ton... (that would be 30/1=30 which makes it 30:1)
will have the same MPG/Ton ratio as a 15MPG vehicle weighing 2 ton... (once again - 15/2 = 7.5 so it's 7.5:1)
How do they have the same MPG/ton ratio? To make them the same (mythbusters addict) we'll do a little experiment.. let's swap some numbers.
30mpg vehicle weighs 2ton, therefore: 30/2 = 15 so 15:1
15mpg vehicle weighs 1ton, therefore: 15/1 = 15 so 15:1
NOW they have the same ratio. This still proves exactly what I said earlier... even if that 30mpg, two ton vehicle weighed only 1 ton (for a reduction of 1 ton of weight over 22 years) The change would appear considerable, in that the ratio would change from 15:1 to 30:1 (30mpg / 1ton = 30, so 30:1)
THE ENGINE is still not any more efficient. It's still only able to net 30mpg, even though there is less work to be done.
HOW, I ask, does that make those numbers anything more than garbled BS that the industry came up with to prove they're making a difference, when in reality they're pocketing the extra money from NOT making a difference?
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You need to control work (F*s) - otherwise, we're not comparing the same thing
We want to compare FE to the amount of work done. Because that's what cars do - turn chemical energy into {hopefully} useful work
I'm going to cheat with my units a little by using something other than conventional
To move 1 ton * 1 mile = 1 ton*mile
To move 2 tons * 1 mile = 2 ton*mile
To do the same amount of work, the 1 ton vehicle needs to move 2 miles....
1 ton * 2 miles = 2 ton*miles
So,
2 miles/ 30mpg = .0667 gallons
1 mile/15mpg = .0667 gallons
This is why loaded semi trucks, trains, ships, etc. are VERY efficient methods of moving "stuff"
Consumption wise, sure - the train eats more than the 30mpg car.... But the car can't move that sort of tonnage
Per pound, the train consumes much much less
It's not the engine that's more efficient - it's the system.