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Help me understand fuel efficiency ...

Discussion in 'General Automotive Discussion' started by juicert, May 12, 2004.

  1. juicert

    juicert Rookie

    Mar 17, 2004
    46
    Ok, so I was barely born at the time, but I seem to remember back in the 70s, during the oil embargo, a number of cars were built and sold that got very good gas mileage - 40-50 miles per gallon, and I thought that for a good part of the 70s and maybe early 80s, that 40-50mpg cars (although small and weak and lame) were not uncommon.

    So, fast forward to today ... the press is going nuts, and people are buying up a lot of toyota and honda hybrids because they get 40-50 mpg ...

    So the question is, if they could do 40-50mpg in the 70s, without any of this wacko hybrid technology ... why does 20 more years of R&D, and the introduction of this hybrid system yield basically zero gains in efficiency over the non-hybrid economy cars made 25 years ago ?

    I really don't get it - I mean, what if you made a late 70s economy car into a hybrid - would it get 70-80mpg ?

    Any comments ?
     
  2. Bryan

    Bryan Formula 3


    Nope and it would be 3-4 times as polluting as a modern car in terms of pollutants other than CO2, e.g. NOx, VOCs, CO. That's a big contributor to what you observe...the focus over the last years has been on cleaning up the exhausts and, with "help" from the gummint, the manufacturers have reduced emissions of non-CO2 pollutants over the last 30 years by 90-95%.
     
  3. juicert

    juicert Rookie

    Mar 17, 2004
    46
    Changing emissions standards was the only possible thing I could think of that would explain that. Thanks for clearing it up.

    I am overjoyed that what has taken place has taken place - that is, the reduction of particulate emissions, etc.

    However, even with that in mind, it sometimes seems like the internal combustion engine is not nearly as technically sophisticated as you would expect it to be, given over 100 years of study and the billions of dollars that the world car market puts into research. You'd think they could have done better than 20mpg with low emissions given the time and resources.

    Sort of disappointing sometimes to think about.
     
  4. PSk

    PSk F1 World Champ

    Nov 20, 2002
    17,673
    Tauranga, NZ
    Full Name:
    Pete
    The other thing to think about is the massively increased weight of modern cars thanks to the increased safety (debateable?).

    The other thing is that these hybrid cars get more than 40-50 mpg more like 70 and the cars in the 70s would have only gotten that mileage if driven very, very, very, very carefully.

    In the end we have gone forward. Motors nowadays are clearner, produce more power and use less fuel. We could always achieve good fuel economy if power and performance suffered.

    I have followed a work mate in a Toyota Hybrid on a motor way and he zoomed along just as good as every other car ... the 70's fuel economy special would still be travelling that same road :D

    Pete
    PS: I owned a Simca 1000 when I was a young chap and that thing was amazing with gas ... 40mpg all the time, but it was not exactly fast compared to modern little cars, ie. 100 mph on a good day. Modern little cars, including all the safety stuff can easily pass 100 mph ...
     
  5. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    6,517
    My first car (1975 Fiat X1/9) would get 33 MPG in the city and 36-37 MPG on the hiway (after I ripped out the emissions gear: 29:33 before)

    Why not more: It had a 4 speed box and 4.44:1 rear end and did 4000 RPM at 65 MPH
    Why not less: It only weighed 1900 pounds (after bumper removal) and only had 72 HP (80 after cam swap*) from 1.3 litre engine 145/85 tires

    A modern econobox has: Better aerodynamics, a 6 speed box to put 60 MPH around 2,000 RPM or lower, a bigger engine, but very precise fuel metering, and a host of friction reducing engineering.

    It is completely possible to put a normal 4-banger engine in a car and get 50 MPG, its just the car can only weigh 2000 pounds, and the engine can only have some 55-75 HP and a size closer to 1.0 litres than the smallest engine available today. And it would sell like crap and have a 0-60 time of 9+ seconds.

    So, in effect, all this hybrid stuff is doing is enabling that small engine to run only when the battery needs a charge and to run when the car is cruising down the road at moderate to thigh speeds. The battery and electric motor/generator just allow the car to go 0-60 in 8 seconds or so in a car of 2600+ pounds

    [*]130 HP after 10.5:1 pistons, 35/75 cam, 2 DCNF 36 Weber's, 4 into 1 exhaust, velocity stacks, "Ohio" legal exhaust (1975).... But milage dropped into the 24 city 28 hiway <he he>
     

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