Overboost is when a turbocharger produces higher-than-normal air pressure, or boost, than the engine is designed to handle. This can cause engine damage, decrease performance, and trigger fault codes. It's not the same as a temporary "overboost" feature that some manufacturers design into the engine to deliver a short burst of extra power; a true overboost problem is uncontrolled and dangerous.
Here are the most common causes for a turbo to overboost:
1. Wastegate Malfunction This is the most frequent cause of overboosting. The wastegate's job is to regulate boost pressure by diverting excess exhaust gas away from the turbine wheel. If the wastegate gets stuck in a closed position, it can't vent the exhaust gas, causing the turbo to spool faster and create too much boost.
- Wastegate Actuator(Internal type): The actuator is the part that controls the wastegate valve. If it's malfunctioning, damaged, or its rod is bent, it may not be able to open the wastegate correctly.
- Wastegate Solenoid: In many modern systems, a solenoid controls the actuator. If the solenoid is sticking or damaged, it can prevent the wastegate from opening.
- Worn Wastegate Valve(External type): Over time, the valve surface or the turbo manifold can wear out, which can also lead to issues with proper wastegate function.
2. Blocked or Damaged Hoses The wastegate system relies on hoses to sense boost pressure and operate correctly.
- Clogged Control Hose: A blockage in the hose that connects the wastegate solenoid to the turbo can lead to an overboost condition.
3. ECU (Engine Control Unit) Issues A "chipped" or remapped ECU can cause overboosting if the new settings are not adjusted properly. While remapping can increase power, it can also push the engine beyond its safe limits if not done correctly, leading to issues like overheating and damaged internals.
4. Sensor Malfunctions Your car's ECU relies on sensors to monitor and control boost pressure.
- Faulty Boost Pressure Sensor: If the boost pressure sensor has defective or corroded connections, it may send inaccurate readings to the ECU, causing it to detect an overboost condition incorrectly.
- Faulty Knock Sensor: A knock sensor monitors combustion. If it's not working properly, it could lead to excessive air entering the cylinders and causing overboost.
What to Do Next:
Overboosting is a serious condition that can lead to engine damage. It's best to stop driving the vehicle and have it inspected by a professional who can diagnose the exact cause. A technician will typically check for fault codes (such as P0234), inspect the wastegate and actuator, and verify sensor functionality to pinpoint the problem.
For those interested in high-performance turbos, Kinugawa Turbo Systems offers a range of performance products, including high-quality wastegate actuators and boost controllers. Our products are designed with durability and precision in mind to help you achieve your performance goals safely. Feel free to explore our selection on our website at store.kinugawaturbosystems.com.