Why are Turbo 4cyl engines Fuel efficient and V6/V8 Turbo’d engines not equivalent or better?
In: 5
Engines tend to be most efficient close to their maximum power and very inefficient at low power. If you experiment with the same car, driven the same way, a small engine will be running closer to its peak efficiency than the larger engine, so a small engine will get better economy.
Now if you drive the car harder and faster with the larger engine then the car’s fuel efficiency will naturally be even lower, because you’re using more power. People that buy more powerful cars tend to use the power more.
It’s important to distinguish engine efficiency from car efficiency. Big engines can be more efficient in terms of fuel going in versus mechanical energy coming out, but people are measuring fuel in versus miles travelled; that’s car efficiency. Heavier cars, accelerating harder and driving at higher speeds use more energy, so miles per gallon can be way down. A large engine can be producing the energy very efficiently but that doesn’t win if the car is using way more energy.
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