Q:Why is it that the upper rpm limit on most street engines seems to be in the 6,000-rpm range? Why isn’t it 5,000 or 7,000, or even 9,000 like a NASCAR motor? Is it material strength, airflow due to the 14.7 psi of ambient air, or something else?
A: For typical overhead-valve (OHV), gasoline-fueled, street engines used in cars and light trucks, a 5,500- to 6,000-rpm redline seems to be the target speed for delivering a satisfactory daily-driving experience at a cost the average consumer can afford. Generally, a typical street engine has about a 1,500- to 1,800-rpm powerband—defined here as the rpm range of separation between the torque peak and the power peak. With the usual street gearing, this yields a vehicle well suited for daily driving. Really heavy,…