High-performance engines that produce maximum torque at high speed use which type of runners?

High-performance engines that produce maximum torque at high speed use which type of runners?

• A. Short
• B. Long
• C. Medium
• D. Variable

Answer: (A)

Short intake runners are best for engines that aim to deliver maximum torque at high engine speeds because runner length tunes the timing of pressure waves in the intake tract. These pressure waves can boost the air density entering each cylinder when the valve opens, but that boost occurs at specific RPMs depending on the runner length. Longer runners tune this boost to lower RPM, helping with low-end or mid-range torque. Shorter runners tune the boost to higher RPM, preserving strong air uptake and manifold pressure as the engine revs higher. For high-speed torque, you want that pressure-boost effect active at high RPM, which is achieved with short runners. Variable-length runners exist to broaden the effective range, but the straightforward way to maximize high-RPM torque is the short runner design.

Short intake runners are best for engines that aim to deliver maximum torque at high engine speeds because runner length tunes the timing of pressure waves in the intake tract. These pressure waves can boost the air density entering each cylinder when the valve opens, but that boost occurs at specific RPMs depending on the runner length. Longer runners tune this boost to lower RPM, helping with low-end or mid-range torque. Shorter runners tune the boost to higher RPM, preserving strong air uptake and manifold pressure as the engine revs higher. For high-speed torque, you want that pressure-boost effect active at high RPM, which is achieved with short runners. Variable-length runners exist to broaden the effective range, but the straightforward way to maximize high-RPM torque is the short runner design.