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Old 03-03-2008, 03:34 PM   #1 (permalink)
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Graph: MPG vs. HP over time in the US passenger fleet

Via Sightline.org

This is really interesting. A graph showing light duty passenger vehicle fuel economy vs. horsepower, weighted by sales volume from 1975-2006.

What it shows is that automakers chosen to build and market (and consumers have chosen to buy) power at the expense of efficiency, with average MPG stalled at around 21 mpg for 25 years:



Quote:
But in the mid-1980s, oil prices fell, the economy picked up, and federal fuel-economy standards topped out. So car manufacturers switched gears, pouring their technological advances into increased vehicle weight and horsepower. As a result, automotive engineers spent most of their time trying to squeeze as much torque and acceleration out of their engines as possible. Efficiency gains stalled at first; and then later, with the rise of SUVs and other light trucks, fleet-wide fuel economy actually went into reverse.
The point of the piece isn't to rail against stalled fuel economy ratings, it was to point out that the pace of technological change in the auto industry (for squeezing ever more power from about the same amount of fuel) has been dramatically rapid.

The implication is that they should be able to deliver dramatic fuel efficiency results, should they chose to go after it with equal zeal.

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Old 03-03-2008, 03:48 PM   #2 (permalink)
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Really? The average power output of 2006 cars was ~220hp?
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Old 03-03-2008, 03:55 PM   #3 (permalink)
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Heck yeah!

Just look at 1975-1981!

The auto industry took FE up 60% in those 6 years alone!

Just listen to the big three whine about raising fleet averages now! They'd like to have us believe that what happened from 75-81 was some sort of divine intervention.
According to them they could never get those kinds of FE gains now.
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Old 03-03-2008, 03:58 PM   #4 (permalink)
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Quote:
Originally Posted by trebuchet03 View Post
Really? The average power output of 2006 cars was ~220hp?
That's not too hard for me to believe. Even "economy" cars now get ~120hp.

Throw in a 500hp corvette Z06 and a few trucks and SUVs with 350hp V8's and you've got a pretty high average.
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Old 03-03-2008, 04:07 PM   #5 (permalink)
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Quote:
Originally Posted by AndrewJ View Post
That's not too hard for me to believe. Even "economy" cars now get ~120hp.

Throw in a 500hp corvette Z06 and a few trucks and SUVs with 350hp V8's and you've got a pretty high average.
It says light duty, so I imagine SUVs (at least most of them) are excluded... Perhaps it includes light duty trucks too... I'm curious if anyone has the sales data of all cars for one year (then I'll work on compiling hp, economy, etc.). How many 500hp vette's are there compared to 110hp econo cars? In my area, at least, I see more cars within the 110-170hp range than 500hp vettes (which is why I'm curious if they really do Halo the stats that much)....

It would probably be more important to look at median rather than average...
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Old 03-03-2008, 05:37 PM   #6 (permalink)
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when you throw in the gm f bodys (between 1998 - 2002 w/ LS1 engine) they made 325 hp and have a slightly better fe than the average on the chart (not much to really comment about but it is there) it raises the hp numbers probably a decent amount (there were tons of them made)

my point is that there may not be 1 specific high horse power car that drew those hp numbers up but probably a mix of quite a few (yes we'll pretend mustangs have a substantial hp also (just kidding if theres any 'stang fans here)) do affect the numbers
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Old 03-03-2008, 06:12 PM   #7 (permalink)
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Quote:
Originally Posted by MetroMPG View Post

The point of the piece isn't to rail against stalled fuel economy ratings, it was to point out that the pace of technological change in the auto industry (for squeezing ever more power from about the same amount of fuel) has been dramatically rapid.

The implication is that they should be able to deliver dramatic fuel efficiency results, should they chose to go after it with equal zeal.
This is a very misleading graph. First of all there is absolutely no correlation between peak HP and and fuel economy at low rpm/low load. Secondly, the graph completely ignores the increasing weight of cars over the years. Even a VW Jetta weighs more than 3000lb and cars need the extra HP just to get out of their own way. Most large sedans weight around 4000lb, more than they ever did in the late 60s to early 70s.
This is not an excuse for stalled fleet wide fuel economy but the connection to increasing peak HP is completely useless.
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Old 03-03-2008, 07:30 PM   #8 (permalink)
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The correlation is that these 2 dimensions are consumer / market driven and here are the annual averages. Maybe power/weight ratio would be better?
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Old 03-03-2008, 08:21 PM   #9 (permalink)
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Weight to fuel economy over time.
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Old 03-03-2008, 08:45 PM   #10 (permalink)
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Quote:
Originally Posted by tjts1 View Post
This is a very misleading graph. First of all there is absolutely no correlation between peak HP and and fuel economy at low rpm/low load. Secondly, the graph completely ignores the increasing weight of cars over the years. Even a VW Jetta weighs more than 3000lb and cars need the extra HP just to get out of their own way. Most large sedans weight around 4000lb, more than they ever did in the late 60s to early 70s.
This is not an excuse for stalled fleet wide fuel economy but the connection to increasing peak HP is completely useless.
I'll agree that the graph is misleading, but I also think (American) cars were getting bigger and heavier before the 1973 oil embargo. Our 1971 Chevy Impala was a 2-tonner :

History of the Impala - Introduction
http://www.goissca.org/imp_hist.htm
Quote:
Year = pounds
1958 = 3,458-3,523
1959 = 3,570-3,665
1960 = 3,575-3,635
1961 = 3,445-3,600
1962 = 3,450-3,920
1963 = 3,265-3,870
1964 = 3,325-3,895
1965 = 3,385-4,005
1966 = 3,430-4,005
1967 = 3,455-3,990
1968 = 3,250-3,940
1969 = 3,640-4,285
1970 = 3,641-3,871
1971 = 3,391-4,021
1972 = 3,720-4,150 -- "In '72, Impala all-time sales topped the 10 million mark, extending its lead as the best-selling full-size car in automotive history"
1973 = 4,087-4,162
1974 = 4,167-4,256
1975 = 4,190-4,959
1976 = 4,175-4,972
1977 = 3,533-4,072 -- "curb weight was cut by more than 700 pounds"

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