Turbo Insights Part 3: About the Intake System of Turbocharged Engines

Original by Honda Magazine | JDM Fans Magazine | Updated: 2024-11-29

In the first part of this series, we explored the history of turbocharging and the working principles of turbochargers. In the second part, we delved into essential components like wastegates and turbo boost controllers. Now, in this third part, we shift focus to the intake system—the other vital side of turbocharging.

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Understanding Turbocharging: A Recap

The turbocharger system works as follows: exhaust gases (5) flow into the turbine (6), spinning the turbine blades, which in turn power the compressor blades. Compressed fresh air (2) is passed through an intercooler (3) to reduce its temperature before entering the combustion chamber (4). This compressed air increases the engine’s efficiency by improving air-to-fuel mixture density.

🔧 Driving Tip:

• At a single moment, turbocharged engines might consume more fuel than naturally aspirated ones. However, over time, turbo engines are more efficient as they can reach desired speeds faster. The key is to avoid constant high loads for fuel efficiency.

Turbo Intake Components

The turbo intake system includes:

• Air Filter (also called "Air Box"),
• Suction Pipe (pre-turbo pipe),
• Blow-off Valve (BOV),
• Intercooler,
• Intake Pipe (post-turbo pipe), and
• Throttle Body.

Suction Pipe vs. Intake Pipe

It’s crucial to differentiate between these two. In turbocharged engines:

• Suction Pipe: Negative pressure side (from air filter to the turbocharger).
• Intake Pipe: Positive pressure side (from the turbocharger to the throttle body).

🔧 Driving Tip: Suction Pipe = Negative Pressure; Intake Pipe = Positive Pressure.

Upgrading Air Filters and Pipes

For turbocharged engines like the Honda L15B Turbo:

• Using high-flow air filters won’t reduce torque. Instead, they optimize airflow and reduce resistance, ensuring better turbo performance.
• Stock air filters (often dense paper) are restrictive compared to performance filters, which are easier to maintain and more cost-efficient over time.

💡 Example:
The L15B7 turbo’s stock suction pipe routes from the left, across the engine, and into the turbo—an inefficient design that aftermarket systems aim to improve.

Blow-off Valve (BOV): Improving Efficiency

The BOV, commonly called the "blow-off valve," is critical for turbo efficiency. Located between the turbo and the throttle, it releases compressed air when the throttle closes, preventing pressure buildup and ensuring smooth turbo operation.

Types of BOVs:

1. Recirculating (internal): Air is re-routed back into the system.
2. Atmospheric (external): Air is vented outside, producing a characteristic sound.

💡 Tip: Upgraded BOVs don’t add power but improve throttle response and airflow consistency.

Cost vs. Performance: Why Stock Parts are Compromises

Manufacturers prioritize cost-effectiveness when selecting components for production vehicles. While upgraded aftermarket parts often outperform stock components, they come at a higher price—something manufacturers consider when scaling production to millions of units.

Next Time

In the next part, we’ll discuss intercoolers, intake pipes, and throttle bodies. Stay tuned for more turbo insights! 🚗💨