There was once a time when turbochargers were common aftermarket parts to improve the fuel efficiency and consumption in a vehicle. Nowadays, turbos have become staple components in many factory-ready engine compartments. Regardless, finding the right turbo for a car, truck, boat, or heavy machinery can be tricky for inexperienced consumers. Fortunately, this guide on how to buy the right turbocharger can help. See how airflow, manifold pressure, vehicle application, single and twin-turbo engines, and types of turbochargers are all important factors for finding the right turbo for your vehicle.
Constant Air Flow
The main component for every turbocharge is constant airflow through a compressor wheel on one side and the turbine on the other. A central cartridge rests between the two along a common shaft with support bearings connecting to the wheels. Inlets and outlets circulate air through the compressor chamber into the intake manifold. From there, the cylinder heads pump vertically and create back pressure which spins the turbine wheel. Remaining gases emit out the exhaust. While this process is effective for virtually all turbochargers, check for any snags or lagging motions when buying yours. Any stalls or inconsistencies with the airflow could lead to overheating and other performance issues.
Manifold Pressure
Probably the most complex turbocharger requirement is the manifold pressure due to its many variables. Consider the maximum engine speed, as well as the engine’s volumetric efficiency, air temperature, and size. An intercooler helps reduce the inner temperature which, in turn, lowers the fuel needed for boost pressure. Volumetric efficiency also helps determine the resulting manifold pressures. It’s the percentage based on the ratio of air flowing through the engine. For example, a volumetric efficiency (VE) of 90% of air flows through the turbocharger while 10% of air is uncaptured.
Part of what feeds into this air inefficiency is compressor discharge, compressor inlet pressure, and the pressure ratio. The pressure between the compressor outlet and intake manifold can be calculated by adding the MAPreq (40.47 psi) with 1 psi or, in other words, adding the MAPreq and the pressure lost between the turbo and intake manifold. The compressor inlet pressure is the resulting ambient pressure minus the loss from the inlet restrictions. Both are important for finding the pressure ratio, which is the compressor discharge divided by the compressor inlet pressure. The right ratio contributes to the exhaust backpressure, spooling, and exhaust housing in cars. Once you’ve found the ratio, you can use these metrics to find the best turbo for your engine.
Matching for Vehicle Application
After calculating the metrics for turbocharger performance, you must match one with your vehicle’s application. Certain cars require specific boost responses that only smaller turbos provide. Other times, trucks or heavy machinery require larger turbos for greater output. Racing vehicles need fast speeds and maximum power efficiency for top-tier performance. Another tip to consider is matching the turbo by fuel type. Specific fuel types pair with different turbos, resulting in optimal compression while reducing exhaust temperatures.
Single vs. Twin Turbo Applications
Buying the right turbocharger also depends on single or twin-turbo applications. Either type has its own power efficiency and output to keep in mind. Engine space can affect the turbo choice for that operation. For example, smaller engines may require single-turbo components to fit the spacing. Nonetheless, decide which turbo best fits your budget and spatial features. Also, consider the horsepower and engine displacement the engine supplies based on the sum of the target inputs.
Types of Turbochargers
With all that said, there are three main types of turbochargers to know: axial flow, radial flow, and exhaust gas. Each of these has their own advantages and disadvantages for performance power and fuel output in certain vehicles.
Axial Flow
Axial flow turbochargers pass fuel through the turbine in an axial direction. This expands the turbo to rotate the compressor. Using a series of axial compressor fans, the turbo compresses air into smaller spaces resulting in greater airflow. While common in large applications, like aircraft or heavy machinery, axial flow turbos have become increasingly common in cars due to their negligence of an intercooler. Axial flow turbos have better air pressure ratios—3:1—than radial flow turbos but are typically heavier and more expensive.
Radial Flow
Alternatively, radial flow turbos, also known as centrifugal turbochargers, force air into the intake system from an impeller while emitting air through a scroll pump. The scroll pump expands the compressor with slow-moving air and gradually increasing pressure. Radial turbos act similarly to superchargers without the step-up gears or belts. Through low pressure at low rpms, radial flow turbos are compact and act even while the engine produces no boost pressure. These types of turbochargers install easily in engine compartments because of their compact size. Unlike axial flow turbos, these do typically require an intercooler to lower compression and exhaust gas temperatures. While their air pressure ratio is relatively smaller than axial flow—1.5:1 or 1.7:1—they also cost less and are lighter weight.
Exhaust Gas
Finally, exhaust gas turbos recycle the gases usually emitted out of the exhaust back into the compressor to power the turbine. As the turbo sucks air into the compressor, it circulates throughout the engine rather than emit outside. Naturally, this process lowers gas emissions and is considered more sustainable than the other types of turbochargers. Additionally, this process increases the volumetric efficiency while reducing the amount of unused air released into the atmosphere.
With that in mind, check us out at TurboTurbos for the best OEM Turbochargers on the market. We proudly offer a wide selection of turbos designed to fit any of our customers' demands. With some of the top brands, our OEM turbos are perfectly designed to increase your engine’s combustion power while reducing carbon emissions. Check out any of our turbos from Acura, Volvo, GMC, Hyundai, Audi, Ford, Subaru, Cummins, Isuzu, and more. You can also call us with any questions and our expert team would be happy to assist you. Whether you’re replacing a worn-out turbo or upgrading an already existing one, stop waiting and find your next turbocharger today.
