Which intake configuration is known to improve exhaust emissions?

• A. Dual-plane
• B. Single-plane
• C. Multi-plane
• D. Hybrid-plane

Answer: (A)

The main idea is how intake runner length and arrangement influence how cleanly the engine breathes at low to mid speeds, which is where emissions are most affected during normal driving. A dual-plane intake uses two groups of longer runners connected to the same plenum. That setup tunes the incoming air so each cylinder receives a steadier, more uniform charge at low to mid RPM. With this more consistent air-fuel delivery, combustion tends to be more complete under light to moderate loads, which lowers pollutants like hydrocarbons and carbon monoxide and helps the exhaust be cleaner. It also helps maintain better low-end torque and throttle response, keeping operating conditions in a range where emissions are easier to control.

In contrast, a single-plane manifold is designed for high-RPM power with shorter runners, which can lead to less optimal cylinder filling at idle and part load, often resulting in higher emissions in those conditions. The other terms aren’t standard configurations for improving emissions and aren’t typically associated with the same emission benefits.