Can a Smaller Turbo Make More Power Than a Big One?

Turbos come in many different sizes and setups.

The size and specifications of a vehicle's turbocharger are dictated by the engine's characteristics. It's not the case that a larger turbo will always make more power. Sometimes smaller turbochargers are a better fit for an engine to produce the most horsepower.

Engine Displacement

The most important factor deciding your turbo vehicle's horsepower is the engine itself. Smaller displacement engines often are fit with smaller turbochargers, as larger turbos require much more exhaust pressure to spool. By analyzing engine displacement and exhaust pressure, a smaller turbo can be fitted to an engine to give it a wider power band with more midrange torque in comparison to a large turbocharger.

Engine Characteristics

Many other engine characteristics have an important role in the horsepower produced by a turbocharger, notably intake temperature and piston compression. A larger turbo may produce hotter charged air than a smaller unit. Certain vehicle's simply will perform better with small turbochargers due to the fact that they can cool the charged air and engine bay more efficiently. Also, the higher an engine's compression, the less turbo boost pressure it will need to produce horsepower, though it also will be less reliable than a properly built low-compression turbo engine.

Turbo Characteristics

Many factors, aside from size, contribute to deciding a turbocharger's ultimate performance. More complex spool and flow characteristics also must be considered. A smaller turbo that spools quickly and flows best in your engine's peak power rpm range can make more power than a less-efficient large turbo.

Tuning

The most important factor in any modern vehicle's performance is the engine's tuning. Without proper tuning, a turbocharged engine is especially prone to poor performance and reliability. As such, a properly tuned small turbo almost certainly will make more power than an ill-tuned larger unit, while also being much more reliable.

References

• Torque Cars: Uprating the Turbo