The Science Of Turbochargers
For many years, turbochargers were appreciated for their capacity to increase horsepower, which made race vehicles or other high-performance automobiles a popular choice. Modern turbos can, however, increase both fuel efficiency and horsepower, improving the efficiency of smaller engines while maintaining their ability to travel at highway speeds. But how exactly does a turbocharger improve an engine's efficiency and power output? An example of a forced induction system that compresses the air entering an automobile's engine is a turbocharger. The benefit of compressing air is that it enables the engine to fit more air into a cylinder, and more air allows for the addition of more fuel. Because of this, each explosion in each cylinder gives you greater power.
In general, a turbocharged engine is more powerful than a similarly sized engine without charging. This can dramatically increase the engine's power to weight ratio. Additionally, a smaller engine may generate more horsepower more effectively, resulting in fewer stops at the gas station. The turbocharger uses the engine's exhaust flow to power a turbine, which in turn turns an air pump to produce this boost. The turbocharger's turbine typically rotates between 80,000 and 200,000 times per minute, which is up to 30 times faster than the maximum speed of most automobile engines. The turbine operates at extremely high temperatures as well since it is connected to the exhaust.
Turbochargers and Engines
Increasing the amount of air and fuel an engine can burn is one of the most reliable ways to make it produce greater power. Adding more cylinders or enlarging the existing cylinders is one approach to achieve this. A turbo can be a simpler, more portable solution to enhance power, especially for an aftermarket component, when these alterations aren't always possible. One of the most reliable ways to boost an engine's power is to increase the amount of air and fuel it can burn. One method to accomplish this is by expanding the current cylinders or by adding new cylinders.
When these modifications aren't always possible, a turbo can be a simpler, more portable alternative to increase power, especially for an aftermarket component. The fact that the power to spin the turbine is not free is one reason for its inefficiency. The limitation in the exhaust flow is increased when a turbine is present. This implies that the engine will encounter greater backpressure during the exhaust stroke. The simultaneous firing cylinders lose a small amount of power as a result.
The engine's exhaust manifold and turbocharger are fastened together with bolts. The turbine, which functions like a gas turbine engine, is spun by the exhaust from the cylinders. The compressor, which is situated between the air filter and the intake manifold, is connected to the turbine by a shaft. The air entering the pistons is pressurized by the compressor. The turbine spins as a result of the cylinders' exhaust passing through its turbine blades. The blades spin more quickly the more exhaust that passes past them. The compressor pushes air into the cylinders from the other end of the shaft to which the turbine is fastened. A type of centrifugal pump, the compressor takes air into the center of its blades and expels it outward as it rotates.
The turbine shaft needs to be carefully supported in order to handle speeds of up to 200,000 rpm. Conventional turbochargers use a fluid or hydrodynamic bearing since most bearings would blow up at speeds like these. The shaft is supported by this type of bearing on a thin layer of oil that is continuously poured around the shaft. This does two things: it keeps the shaft and several other turbocharger components cold, and it reduces friction when the shaft rotates. But too much boost can be harmful. There is a greater risk of knock since the turbocharger pumps air into the cylinders under pressure, which the piston then further compresses. As air is compressed, its temperature rises, which causes knocking.
Before the spark plug fires, the temperature may rise sufficiently to ignite the gasoline. In order to prevent knock, cars with turbochargers frequently require higher octane fuel. If the boost pressure is extremely high, the engine's compression ratio may need to be lowered to prevent banging. Between the turbocharger and the cylinder, the turbo system could also use an intercooler. This lessens the likelihood of knock by cooling the air before it enters the combustion chamber. The design of a turbocharger for an engine involves a lot of trade-offs. We'll examine some of these concessions and their effects on performance in the following section.
Turbochargers Taken Apart
The fact that turbochargers do not instantly increase power when you press the throttle is one of their biggest drawbacks. Before boost is produced, the turbine must first reach its maximum speed. When you press the gas, you initially notice a lag before the car accelerates quickly as the turbo gets going. A wastegate, which is included on the majority of automobile turbochargers, enables the use of a smaller turbocharger to reduce lag while keeping it from spinning too quickly at high engine speeds. The exhaust can bypass the turbine blades thanks to the wastegate, a valve.
The boost pressure is detected by the wastegate. The wastegate bypasses some of the exhaust near the turbine blades to allow the blades to slow down if the pressure rises too high, which may be a sign that the turbine is spinning too quickly. In some turbochargers, the turbine shaft is supported by ball bearings rather than fluid bearings. These, however, are not your typical ball bearings. They are extremely precise bearings built of cutting-edge materials to withstand the turbocharger's speeds and temperatures. Compared to the fluid bearings found in the majority of turbochargers, they enable the turbine shaft to spin with less friction. They also enable the adoption of a somewhat shorter, lighter shaft. By accelerating the turbocharger more quickly, turbo lag is significantly diminished.
More Turbochargers More Parts
Some engines employ two different-sized turbochargers. While the larger one takes over at higher engine speeds to generate more boost, the smaller one spins up to speed extremely rapidly to reduce latency. Air heats up when it is compressed, and it expands when it heats up. Thus, warming the air before it enters the engine contributes to some of the pressure rise caused by a turbocharger. Increased air molecules must enter the cylinder, not necessarily more air pressure, in order to boost engine power.
An extra part that resembles a radiator called an intercooler or charge air cooler allows air to travel through both the interior and exterior. While cooler air from the outside is fanned across fins by the engine cooling fan, intake air travels through sealed passageways inside the cooler. By chilling the pressured air leaving the compressor before it enters the engine, the intercooler boosts the engine's power even further. This means that the intercooled system will inject 7 psi of cooler air, which is denser and contains more air molecules than warmer air, if the turbocharger is working at a boost of 7 psi.
At high elevations, where the air is less thick, a turbocharger is also beneficial. Because the engine receives a lower mass of air with each piston stroke at high altitudes, normal engines will have less power. Although a turbocharged engine may also see a decrease in power, the effect will be less pronounced because the turbo's capacity to compress air will largely counteract the effects of the thinner air. Modern automobile fuel-injection systems automatically increase fuel flow if a turbo is installed because they rely on oxygen sensors in the exhaust to detect whether the air-to-fuel ratio is correct.
A fuel-injected vehicle may not have enough fuel if a turbocharger with excessive boost is fitted to it. Either the pump and injectors are unable to supply it, or the software that is built into the controller will not permit it. To make use of the turbocharger to its full potential in this situation, additional changes will need to be performed.