yeah, the tier 1 cars are no match for tier 3 cars.
the game hints before the races say that too.
def. dont expect to beat the game with the first car u pick-up
i went rx-8 -> rx-7 -> lotus elise -> lambo merciallago
i have some others, but i primarily used those, i highly reccomend the elise, and just do every upgrade possible to it and u will get very close to the end with it.