"Sport" and "performance" are one and the same, my friend. Acceleration and top speed figures don't differentiate between the two. Sure, there's performance in power, but there's also performance in handling. If you ask me, "sport/performance" defines any car that was designed to do much more than just the daily grind. Why stiffen the suspension in a Clio RS or stick a limited slip differential in a Prelude Si? What could your mom possibly get out of those features, let alone a boost in power over the base models, on her drive to work or the store?
LSD: for driving in the rain (that's my excuse for the wife...).
Stiffer suspension: A base Mazda3 or Honda Civic has a stiffer suspension than a Corolla, (stiffer, actually, than some sportscars), but they're not performance cars, or sold as such.
More power: Honda Accord V6: near-300 hp, not conceivably a performance car in any way. Too wallowy. Too soft.
Most cars beyond the basic Yaris are built to do something more than just commute. That's what sells cars... added value.
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A 1989 MX-5 has
less acceleration than most compacts with the same engine size,
less grip and the brakes of a milk truck. A comparable hot hatch could run rings around it on most tracks. It's still a sports car.
My four-door family sedan (unmodified) would be able to lap a Daihatsu Copen within just one or two laps around any race track short of an autocross with gates two inches wider than my wing mirrors. (even then, it'll be close) But technically, my sedan is not a sports car. A Copen is.
A sports car, going by strict textbook definitions, is a one or two seat car that's low, light and built to drive at high speeds. An even stricter definition is 2-seat, 2-door. An even stricter one is it must be open-topped.
Famine is pointing out that eight6er's
personal definition of "sportscar"
excludes cars which
are sportscars by the classic definition.
And "performance car" connotates "high performance"... it's an even weirder term that has no agreed upon definition other than a car labelled a "performance" car has to meet some undefined set of criteria for it to be considered "performance."
What are those criteria? What percentage faster, grippier, brakier or powerfull-...er over an ordinary car does a car have to be to be considered a "performance car"? Your definition that it has to do much more than just commute captures the flavor of it, but Famine was debating eight6er's use of the term.
It's one of those terms coined by people to label cars they don't think of as sports-cars... much like "sport compact" or "sport coupe"... whoop-de-doo... a sports-coupe meets 99% of the requirements to be called a sports car... and some sports-coupes are sports compacts.