Below shown is the Torque & Power curve of a Car. You can observe tat the peak torque is at 200Nm@3900rpm & peak power is at 130hp.
Now, check the third curve SPECIFIC FUEL CONSUMPTION. From the graph we can tell tat max fuel efficiency ( least SPECIFIC FUEL CONSUMPTION) is at max torque, & also it is said tat the max performance of the car ( which include power & fuel efficiency) is at the range between rpm @ max torque & max power. This graph varies for different car. For the car shown above, the max performance is from 3900rpm to 5100rpm. This means tat the car (engine & transmission) was designed for this particular rpm band width.
I Own a Fiat Palio MultiJet 1.3D, which I call the “Beast”. For my Beast, the max torque is at 18.8 @ 2,000 (kgm@rpm) & Max power is at 75 @ 4,000 (PS@rpm).
(http://www.cardekho.com/specs/Fiat_Palio_Stile_Multijet/Fiat_Palio_Stile_Multijet_1.3_SD-specification.htm ) This means my Beast was designed for 2000rpm to 4000rpm. It means, if i drive the car after 4000rpm, the power output of the car decreases. Though the car engine would run at very high rpm, the power output of the car decreases. So, avoid driving after Peak power rpm, which could heat up ur engine very quickly.
One more thing to consider, the Beast is fitted with a Turbocharger which kicks open at 2000rpm. This is the reason the peak Torque of Beast is given at 2000rpm. If you have driven a turbocharged car, you would have felt a sudden pull of the car at a Particular rpm. This is called the Torque which is nothing but the Peak Torque in this case.
When this band width is low, we can tell tat the car is very highly tuned. Maybe used for racing or rally. Generally this bandwidth is kept large to facilitate all type of driving style when designing a Passenger Car.
Drive Fast-Drive Safe
-Bopsi
