Can a Three-Cylinder Engine Be Modified into a Four-Cylinder Engine?

[SanAlessandra]

A three-cylinder engine can theoretically be modified into a four-cylinder engine, but the modification cost is relatively high, and reliability cannot be guaranteed. Below are the differences between three-cylinder and four-cylinder engines: 1. The number of engine cylinders differs—three-cylinder engines operate with 3 cylinders, while four-cylinder engines operate with 4 cylinders; 2. The overall weight varies—because a three-cylinder engine has one fewer cylinder, it is lighter than a four-cylinder engine; 3. Fuel consumption differs—for vehicles of the same body weight, due to differences in overall engine weight and working cylinders, a three-cylinder engine consumes less fuel than a four-cylinder engine; 4. Manufacturing time varies—the smaller size and weight of a three-cylinder engine result in a shorter manufacturing time compared to a four-cylinder engine; 5. Efficiency differs—the output power of a three-cylinder engine is essentially the same as that of a four-cylinder engine, so its efficiency is much higher; 6. Engine smoothness varies—the overall performance of a four-cylinder engine is superior to that of a three-cylinder engine; 7. Maintenance costs differ—due to differences in cylinder structure and size, the maintenance costs for a three-cylinder engine are lower than those for a four-cylinder engine.

[Brayden]

This job is definitely not for the average person! Converting a three-cylinder to a four-cylinder sounds cool, but the engine bay structure is completely different—the new cylinder block won’t fit into the original space. You’d need to custom-make the cylinder block, crankshaft, piston-connecting rod assembly, and then match it with the transmission and ECU. The whole process would cost at least 70,000 to 80,000 RMB. What’s worse, the modified car would never pass the annual inspection, and traffic police would impound it on the spot. I know a seasoned car enthusiast who tried this and ended up spending three times more than just buying a factory four-cylinder car, not to mention the idle vibration was as rough as a tractor. Honestly, I’d advise you to just get a factory four-cylinder car—it’s way more reliable and safer.

[MariaRose]

Having been in the modification business for over a decade, I find the idea of converting a three-cylinder engine to a four-cylinder utterly absurd. The number of cylinders is determined during the design phase, and adding an extra cylinder bore would compromise the engine's structural integrity. Even if you forcibly install a four-cylinder engine, you'd need to reprogram the ECU parameters, and the fuel consumption and power matching would be a nightmare. Look at those modification showcases on TikTok—how many dare to tamper with the cylinder count? Last time, someone spent 50,000 yuan modifying a Honda Fit, only to have it seize up on the highway. Even the modification shop owner admitted it was beyond their capability, suggesting it's better to source a used four-cylinder engine assembly for a swap—more practical and legal.

[VonGiselle]

Stop dreaming, this isn't just about replacing a part! A three-cylinder engine lacks an entire combustion chamber compared to a four-cylinder, and even the crankshaft angles don't match. To actually modify it, you'd have to disassemble the engine down to just the casing, which is equivalent to building a new engine from scratch. Regular tuning shops don't have the expertise for this—you'd need to go to a racing factory for custom parts. Plus, after the modification, the sudden increase in horsepower would overwhelm the stock brakes and suspension, turning the car into a moving bomb. The money saved from skipping this modification could buy you a brand-new Corolla, so why bother?