There are other aspects of the car's design such as keeping the flow of air attached to the body far to the back of the car as possible to minimize pressure drag (the Bernoulli relationship). A design with less drag means higher efficiency and an increased maximum speed, given the same powertrain.
The car's design focuses on minimizing air resistance by keeping airflow attached to the body as far back as possible, which is related to the Bernoulli effect. This reduces drag, leading to better fuel economy and higher top speeds when using the same engine.