On Monday, July 02, 2007 13:19, Chris Barker wrote:
> Hmmm, what a strange way to go about building cars, although I always
> thought "final drive ratio" referred to the end of the drive train
> rather than the gearing of the complete system.
>
> The only real difference between auto and manual should be the slip
> in the torque converter, but I'm no car engineer :-)
>
> Chris
Snip
> >. Almost all automatic transmission cars have higher
> > final drive ratios which help the mileage compared to the lower
> > geared manual transmission versions. That gearing also hits their
> > acceleration. In real use the manual transmission cars are not only
> > quicker, but they get better fuel economy. The fuel economy by real
> > drivers part can be checked at:
I'm just getting caught up on the list email. The reason automatics are, or
theoretically can be, geared higher is that the torque converter provides a
two to one torque gain at maximin slip. The US market swapped primarily to
automatics over market demand, which means that an automatic will have a much
higher trade in value. (Take this as you would any generalized statement,
there has to be exceptions to this.) US car companies were also having a
tough time making a carbrated manual car meat emissions standards.
The biggest factors are still a combination of the driver, weight, gearing and
wind resistance. A driver that winds a car to the red line on every shift is
going to get less mileage and longevity than one that doesn't. A light,
small, lower powered gas(petrol) car will have better fuel economy that a
big heavy diesel.
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