What is turbo lag and how do I avoid it?

In the never-ending quest for higher efficiency and smaller engines, in recent years the turbocharger has become a popular choice for car manufacturers. We are starting to see turbos in just about every type of car and every engine configuration available. While most new car manufacturers have developed systems to negate the dreaded turbo lag (such as twin turbo systems and anti-lag), it still exists. Read on to find out what turbo lag is and how to fix it.

What are turbos and how do they work?

A turbocharger (affectionately known as a turbo) is used to force extra air into an engine. This helps the engine to create more power and improve engine efficiency. To do this, the turbo uses exhaust gasses from the engine to spin a turbine, “spooling” up the turbo. This turbine is connected on a shaft to another turbine in a separate housing which sucks in and compresses air. This “charged” air is usually sent through a heat exchanger (similar to a radiator) known as an intercooler to cool the air. Cold air is denser than hot air, allowing more oxygen by volume, increasing efficiency. This cool, pressurized air (known as boost) is then forced into the engine, creating more power.

What is turbo lag?

In short, turbo lag is the delay between pressing the accelerator and feeling the turbo kick in. This usually takes about 1 second in newer cars. When you open the throttle (press the accelerator), it takes time for the exhaust gasses to spool the turbo turbines up to the correct operating speed (Usually around 80,000 to 120,000 RPM) and provide the engine with the required boost level for maximum performance. Ideally, as soon as you press the throttle, the turbo would already be at operating RPM.

What causes turbo lag?

Turbo lag is an inherent failing of the turbocharger design. Car makers have done their best to reduce turbo lag from the factory, however a car’s turbo lag can increase over time. This comes down to a number of factors, but common reasons for an increase in turbo lag can be:

    • An exhaust leak. If there is an exhaust leak before the turbo (e.g. In the exhaust headers) there will be less exhaust gas to spool the engine, leading to increased turbo lag
    • A boost leak. A boost leak occurs when charged air from the turbo leaks out instead of entering the engine. Boost leaks can easily be created over time between turbo piping connections, as they are under high levels of pressure.
    • A faulty wastegate. The turbo wastegate controls the maximum amount of pressure the turbo creates, diverting excess exhaust gasses from the turbo to stop overboosting. A waste gate that can’t close fully under low boost scenarios will increase turbo lag.
    • A faulty boost solenoid. A boost solenoid controls the amount of boost seen by the wastegate, allowing it to open only at the desired pressure. If your solenoid is stuck open, your turbo will likely run at a dramatically lower boost level and increase lag.
    • Lean air-fuel ratios (AFRs). Not only is a lean air-fuel mixture bad for your engine, it can cause your engine to run less efficiently, increasing lag. Low AFRs are commonly caused by faulty injectors, failing fuels systems or a malfunctioning O2 sensor.
    • Excessive engine wear. As anything gets old, it becomes less efficient, and the same can be said for your car’s engine. Usually the amount of engine wear over time is minimal, but poor maintenance can cause significant increases in turbo lag over an engine’s life.

How to avoid turbo lag

The easiest way to avoid turbo lag is to have your car regularly serviced. Servicing your car reduces component wear, allowing your engine to operate as efficiently as possible. If you notice any odd sounds, vibrations or sudden increases in turbo lag, you should have your car examined by an experienced mechanic. It may be experiencing some of the issues discussed above, including a faulty wastegate or an exhaust leak. These are all relatively easy issues to fix, bringing your car back to life and avoiding the annoying turbo lag.
If you’re ready to book in for a service, contact the team at Australian mechanical today.

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