Why are today's cars faster when old cars had more horsepower?

Dear Tom and Ray:

Over the years, I have enjoyed reading your column every week and have learned a
few things from you about cars. As an old shade-tree mechanic, however, I also
saw you make a mistake awhile back. "Larry" wanted to know why today's cars are
faster, even though cars of the 1960s (like his '68 AMC Javelin) had more
horsepower. Your answer had to do with the car's power-to-weight ratio. But
that's only partially correct. In 1972, all cars' horsepower ratings, previously
reported as "indicated" (or some other meaningless measure), were changed to
"net." "Net horsepower" is the true horsepower the engine delivers in the vehicle
-- the actual amount of power delivered to the engine's flywheel, transmission or
driven wheels, accounting for horsepower losses due to friction and the addition
of accessories. As a result of this change to "net horsepower" ratings, the
horsepower listed for the 1968 Javelin is inaccurately inflated by today's
standards. In other words, those cars didn't have as much horsepower as we
thought they did in the '60s. Hope you'll pass this correction along to your
readers. -- Victor

RAY: You just did, Victor. Thanks.

TOM: You mean my 1952 MGTD doesn't REALLY have a whopping 53 horsepower?
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