What is the difference between a three-cylinder and a four-cylinder engine?

[SanEvelyn]

Here are the differences between a three-cylinder and a four-cylinder engine: 1. Fuel consumption: Due to its structural advantages, the three-cylinder engine excels in fuel consumption control. Its compact size results in higher power density and improved thermal efficiency. The three-cylinder design reduces pumping losses, and its smaller size also minimizes friction losses during operation, leading to lower heat dissipation losses. 2. Power performance: Within the 1.0L-1.5L displacement range, the three-cylinder engine has larger individual cylinder volume compared to a four-cylinder engine of the same displacement, providing better low-speed torque. Fewer cylinders mean less mechanical friction, and increasing the number of cylinders can reduce single-cylinder efficiency. The three-cylinder engine offers faster power response and stronger performance compared to a four-cylinder engine. 3. Turbo lag: The three-cylinder engine experiences less exhaust interference than a four-cylinder engine. When paired with small-inertia turbo technology, it delivers better low-end torque and reduced turbo lag compared to a four-cylinder engine.

[LaMolly]

My brother and I have pondered this many times at the auto repair shop. A three-cylinder engine has one less cylinder than a four-cylinder—it's like reducing a four-person team to three, inevitably leading to more fatigue and vibration. But nowadays, automakers are clever; they've added balance shafts and hydraulic mounts, making it hard to tell the difference at idle in new cars. The most noticeable distinction comes when revving: three-cylinders sound a bit raspy, while four-cylinders sing more smoothly. As for fuel efficiency, a three-cylinder might save a fraction of a liter compared to the same displacement four-cylinder, but the savings at the fuel cap are negligible compared to maintenance costs—three-cylinder engine mounts wear out faster, and if the steering wheel shakes on rough roads, it's time for a replacement. Recently, I tried a new three-cylinder hybrid, and with the electric motor assisting, it actually felt quite smooth.