August 31st, 2016 by

We already know that horsepower is how fast your engine can do work, but if that’s the case, why do some high horsepower vehicles have a slower top speed than some low horsepower vehicles?

The key is power-to-weight ratio.

The less weight the horsepower generated by the engine has to move, the faster the vehicle will go. So, a heavy truck with a big V8 engine could have the same ratio as a smaller vehicle with a smaller engine. The key to making a sports car with swift acceleration and a high top speed is a big engine and a lightweight body.

Yet, therein lies the problem. The catch-22.

To generate more horsepower, you need a bigger engine. A bigger engine weighs more, bogging down the ratio. Many sports cars, like the BMW M5, are actually quite heavy. The BMW M5 weighs 4,387 pounds, which is heavier than some full-size pickups! Yet, its V8 engine cranks out a blisteringly high 575 horsepower, for a ratio of 7.6 pounds per horsepower.

By comparison, a good pickup truck has a ratio of around 13 pounds per horsepower, and a small non-luxury sedan averages around 23 pounds per horsepower. The lower the ratio, the better your speed.

Learn more about how to get the most power and performance out of your pre-owned BMW at Tulley BMW of Manchester.

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