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human
ELI5: Mechanically, what is the difference between a Hummer and a Ferrari?

They both have a high amount of horsepower, but one of them uses it to tow heavy loads while the other uses its high horsepower to go really fast. What makes them so different?
gpt
Actually, Hummers generally do not have a high amount of horsepower. The standard engine used by the US military HMMWV has a 6.5L diesel V8 that produces 160 HP at 3,400 RPM and 290 lb-ft of torque at 1,700 RPM. For comparison, the Ferrari 458 has a 4.5L gasoline V8 that produces 562 HP at 9,000 RPM and 398 lb-ft of torque at 6,000 RPM. 

The difference between torque and horsepower is very important. Torque is the rotational force of the engine, and horsepower is how rapidly an engine can do "work". In this case, "work" means force applied over a distance. So, to simply move a heavy load, you need torque. To move something *quickly*, you need horsepower. You'll notice that the Ferrari has higher peak horsepower than torque, and the Hummer has higher peak torque than horsepower. 



Another thing to notice is the RPM values for peak torque and peak horsepower. The Hummer's engine is better at relatively low RPMs, especially torque (peak torque is at only 1,700 RPM). The Ferrari's engine excels at higher RPMs. Most normal driving is done at relatively low RPMs because this is more efficient. If you want to move something heavy at normal speeds, you want your torque fairly low in the RPM band.

The Ferrari's engine does have higher peak torque than the Hummer, and could probably be engineered into a vehicle that can pull a heavier load than the Hummer. However, it gets its max torque at 6,000 RPM, which is pretty high (many normal cars redline at around 6,000 RPM). Constantly running the engine at that speed is inefficient and would not be good for longevity and reliability of the engine.