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How to Reduce Turbo Lag in Diesel Engines?

Posted by Scott Goldfarb on

The turbo increases the engine's power by allowing it to receive more air. It is a beneficial component for diesel engines because they tend to have lower power outputs. Knowing how to reduce turbo lag in diesel engines can improve their performance.

How to Reduce Turbo Lag in Diesel Engines

Turbo lag is the time between pressing the throttle and feeling the surge of power by the vehicle. Internally, it is the time it takes for the turbocharger to generate sufficient boost to provide a noticeable acceleration.

The lag can be big or small because of various factors. In the article, we will explore those reasons and how to improve the performance by decreasing the lag.

The turbo generally lags because it takes time for the exhaust gasses to build up and spin in the turbine. This is particularly noticeable when the exhaust gas flow is lower at slower speeds.

Another factor that can reduce the turbocharger’s responsiveness is its size. Bigger turbos require higher exhaust flows to reach their optimal speed. The shape of the turbine and compressor can also be a significant factor in lagging.

One factor alone won’t provide a significant improvement to the lagging. You should instead look to implement improvements to multiple things.

1. Optimized driving

The turbos produce maximum torque in the 2000 RPM to 4000 RPM range. Pressing the throttle below that range will likely cause a delayed response to the surge in power. This is entirely down to the driver's habits; you can apply this instantly without any cost.

Build up the engine’s speed gradually to the necessary range to produce maximum boost. This way, you will feel the improvement once you step on the throttle. Sudden aggressive surges can suffocate the turbo and increase the lag.

2. Upgrading the air filter

You can do this on your own if you’re moderately crafty with vehicles. Upgrading the air filter to a cartridge-style air filter will improve the responsiveness by improving the filtration and the airflow. 

Look for a filter that’s compatible with the engine model and opt for one that increases the airflow capacity. This will allow the engine to breathe more freely and can help minimize lagging. You should also select the filter by its durability and capacity for reusing. 

Upgrading the air filter

Source: shutterstock.com / Photo Contributor: Charles Knowles

3. Tuning

While the previous two methods were relatively cheap, tuning would cost you anywhere from a few hundred to several thousand dollars, depending on your vehicle and the type of tune-up.

You may want a better fuel economy or be more interested in having more power and torque. Different options for tuning allow you to optimize the car’s performance for various tasks. Therefore, you should tell the tuners you wish for better responsiveness.

Optimizing the settings to enhance low-end torque and the turbocharger response efficiently reduces the turbo lag. Well-equipped mechanics can optimize the performance by modifying the engine’s software to adjust the injection timing and boost levels.

4. Fuel system upgrades

Upgrading the injector and fuel pumps will improve combustion efficiency. This will undoubtedly lead to reduced lagging because there will be a better low-end torque.

Good injectors provide a more precise fuel delivery in time and amount. A better fuel pump will ensure the supply can flow at a higher pressure rate to enable an increase in power. An upgraded fuel pressure regulator will help prevent pressure drops which can cause lags.

5. Upgrading the exhaust system

The exhaust system comprises the exhaust manifold, catalytic converter, exhaust pipes, muffler, resonator, and tailpipe. Replacing some of these parts with aftermarket options can improve the engine's performance.

Exhaust manifold

Replacing the exhaust manifold with one that has bigger and smoother tubes can enhance the exhaust flow. This reduces the backpressure and can help the engine spool up faster.

Catalytic converter

Upgrading to a high-flow catalytic converter can improve the exhaust flow. This reduces the influence of the backpressure on the turbocharger, cylinders, and exhaust gas flow.

Other upgrades to the exhaust system

Multiple improvements will reduce the turbo lag and improve the engine's overall performance. Installing larger-diameter pipes, high-performance mufflers, and a larger-diameter downpipe will improve the overall engine efficiency and reduce the turbo lag.

6. Increasing the compression ratio

The compression ratio is the volume difference of the combustion chamber between the piston being up and down. A bigger compression ratio would deliver a better air-fuel mixture because compressed air occupies a smaller volume, allowing more air to enter the chamber. 

A higher compression ratio will provide faster combustion and enhanced thermal efficiency. It’s important to note that a higher compression ratio will increase the engine's demands for maintenance and fuel quality.

7. Intercooler upgrades

Cooling the compressed air before it enters the engine means it will have higher oxygen levels. You can upgrade the intercooler in size or design. A bigger intercooler will provide better cooling because it can cool more volume of air.

Materials such as high-quality aluminum or carbon fiber can improve heat dissipation and the cooling system.


Source: shutterstock.com / Photo Contributor: Nixx Photography

8. Replacing the turbocharger

Replacing the turbocharger with more powerful alternatives that significantly improve performance can reduce the lag. Twin-scroll turbo, VGT, and electronic turbo are all great for achieving the target and work in different ways.

Twin-scroll turbo

The divided exhaust housing of the twin-scroll turbo separates the exhaust gas into two channels. This separation is helpful because the exhaust gasses from each cylinder can better push the turbine wheel. This allows the turbocharger to produce more power for the engine, allowing better and more timely acceleration.

Variable geometry turbo

VGTs have flexible turbine vanes that can adjust automatically depending on the demands of the car. When the engine needs more power, the vanes will allow more exhaust gas flow. During lower demand for power, the vanes close to maintain the balance between flow and pressure.

Electric turbo

An e-turbo has an electric motor that helps the turbocharger supply the engine with power and can help with reducing turbo lag. The motor helps by spinning the compressor wheel even at lower engine speeds. This process improves the throttle response by a significant amount and reduces lag.

Electric turbo

Source: shutterstock.com / Photo Contributor: Evannovostro

Related article: How to Install a Turbo on a Diesel Engine?

9. Compound turbocharging

This method involves using more than one turbo. Most common designs involve a smaller, low-pressure turbo that provides the initial boost at slower speeds and a higher-pressure turbocharger that boosts at higher speeds.

Compound turbocharging can effectively decrease turbo lag and improve the engine's overall performance.

10. Proper maintenance

The most obvious yet neglected method of all. Regular maintenance can be all you need to reduce the turbo lag effectively, as taking care of your engine is the most important factor for a high-performing car. 

Here are the most relevant ways you can preserve your engine:

  • Regular oil changes
  • Air filter maintenance 
  • Fuel filter replacement
  • Cooling system maintenance
  • Exhaust system inspection
  • Boost pressure system checks

Lack of maintenance is the reason for many engine malfunctions and suboptimal performance. If your car has clogged air filters, accumulated fuel system issues, problems with cooling, or bad timing, then turbo lag would be the last thing to worry about.

However, if you take timely care of your engine, your car will run on optimal performance, including a decreased turbo lag. 

You should change your oil every 5,000 to 7,500 miles, or six months. You should replace air and fuel filters once a year while coolant every three years. 

11. Water or water-ethanol injections

This method provides an instant cooling of the fuel-air mixture through an injection into the combustion chamber or the intake air stream. This technique lowers the temperature and thus provides more oxygen during combustion.

12. Tire pressure

Underinflated tires create more friction with the road surface. This forces the engine to work harder to overcome the energy loss and continue moving at the desired speed. The increased workload can lead to slower acceleration and an increased turbo lag.

Tire pressure

Source: shutterstock.com / Photo Contributor: Pakpoom Phummee

12. Weight reduction

Lowering the weight of your car will reduce the turbo lag, but it doesn’t mean you will have to trim essential stuff. Instead, you can replace heavy objects with lighter alternatives, like carbon fiber seats, lighter exhaust, brakes, wheels, sound systems, etc.

Trimming unnecessary weight will also improve fuel efficiency, acceleration, and handling. Do not compromise your safety with your actions to reduce the vehicle's weight.


The turbocharger’s role is to provide a needed boost to the engine. Sometimes delays can happen from the pressing of the gas pedal to the time the boost is felt. This occurs because it takes time for the turbo to generate sufficient power and torque.

Numerous factors determine how long the lag will be, and some, like the driving style of the car’s owner, can be immediately altered for better performance. 

Other ways to reduce turbo lag in diesel engines are replacing the turbocharger with a better one, upgrading the intercooler, increasing the compression ratio, tuning the engine, and upgrading the fuel and exhaust systems.


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