Talking about ways of improving an engine’s power without adding much weight; turbocharging is one of the most common methods of achieving that. If you’ve been hearing the terms turbo and turbocharged that’s been tossed around especially when talking of super cars and sport cars, basically talking about improved performance and engine efficiency, turbochargers are mostly considered.

In this article well be talking about turbocharger –defining turbochargers and how they work and improve engines performance.

What’s a Turbocharger

Turbocharger is a type of forced induction system used on internal combustion engines, it’s a device that improves engine power output by forcing compressed air into the engines combustion chamber (cylinder). The compressed air allows the engine to take more volume of air and also the amount of fuel injected can be increase, this will result to more explosion in each cylinder and therefore increasing the power output of the engine. A turbocharged engine is able to produce more power than the same engine without a turbocharger compared to the weight of the engine. There’s a turbine in the turbocharger that spins up to about 150,000 rotations per minute the rotation is about 30 times the rotation a normal engine can reach.

To add more power to a normal engine, one of the surest way is to increase the amount of air and fuel mixture the engine burns, and this can be done by adding more cylinders or making the cylinders larger, but this method may not be feasible, a turbocharger is more simpler and compact way to achieve the power boost.

At sea level the atmospheric pressure is 14.7 psi (pounds per square inch) and the turbocharger is able to provide a boost of 6 to 8 psi, you can see with the turbocharger you’re able to get about 50% more air into the cylinders, which means you can get up to 50% more power boost. It’s not perfectly efficient enough but you can still get a 30 to 40% boost instead.

Why the reduction in the expected power output is because the turbocharger also really on the engine power to spin the turbine which is connected to the exhaust line. The turbine spins from the pressure of the exhaust gas. This mean on the exhaust stroke the engine has to push against back-pressure caused by the turbine resulting to subtraction of power from the cylinders that are firing at the same time.

How does Turbocharger Works

Basically, a turbocharger is just an air pump that pumps in compressed air into the engine cylinders.

The turbocharger is bolted to the exhaust manifold of the engine, hot exhaust gas from the engine passes through the blades of the turbine of the turbocharger causing the turbine to spin. The more exhaust gas that goes through the blades, the faster the turbine will spin.

The turbine is connected to the compressor by a shaft, as the turbine spins the compressor also spins. The compressor is located between the air filter and the intake manifold. The compressor works as a centrifugal pump, it pumps the air into the cylinders by compressing and pressurizing the air into the cylinders.

As earlier said, the turbocharger is able to spin up to 150,000 rpm (rotation per minute). For the turbocharger to be able to handle speed as high as this, that means friction must have been minimized as much as possible, the turbine shaft is the part that needs be carefully supported. Most bearings will not be able to handle high speed as this so what most turbochargers use is fluid bearings. This type of bearing supports the shaft on a thin layer of oil that’s constantly pumped around the shaft. The oil doesn’t only serve as the lubricant, it also perform the work of cooling the turbocharger parts, because the hot exhaust gas will heat the turbocharger up very fast.

Defects of turbocharger

It was stated earlier, that the turbocharger causes a back pressure on the exhaust gas, but the problem of back pressure is solved because of gas expanding at the same time in the other cylinders.

Turbo lag

One of the main problem of turbocharger is turbo lag, turbo lag is due to the fact that turbochargers do not provide the boost immediately when you step on the throttle. Turbo lag is the delay to the increase in power output in response to a throttle change, it’s because it takes the turbine a second to get to the speed where boost can be produced. This gives a feeling of late throttle response when you step on it and it takes a second to get response.

The way to solve the problem of turbo lag is to reduce the inertia of the rotating parts, and that’s by reducing there weights. The low inertia of the rotating parts will allow the compressor and the turbine to accelerate fast enough to start providing the boost early. The common way of reducing the inertia of the turbine and compressor is to make the turbocharger smaller. A small turbocharger will provide boost more quickly and at lower engine speeds. But a small turbocharger may not be able to produce more boost at higher engine speeds. A small turbocharger is also in danger of spinning too fast at higher engine speeds, when there’s a lot of exhaust gas passing through the turbine.

One way to make the small turbocharger applicable and without the problem of speeding too fast is the use of wastegate. The wastegate prevents the turbochargers from spinning too quick, so the turbocharger makes it possible to reduce turbo lag by using smaller turbochargers that won’t speed too fast. The wastegate senses the boost pressure, if it gets too high, it means the turbine is spinning too fast. The wastegate is a valve that allows the exhaust to bypass the turbine blades, it bypasses the exhaust gas around the turbine blades, allowing the blades to slow down.

Some turbochargers don’t use fluid bearings, they use some advanced ball bearings that are able to regulate the speed and temperature of the turbocharger. The ball bearings are super-precise bearings made of advanced materials, they allow the shaft to spin with less friction than most fluid bearings will.

Another way to reduce turbo lag is to use ceramic turbine blades which are lighter than steel blades, the lesser weight means the turbine can speed up quickly thereby reducing turbo lag.

The danger of knock

One other challenge of turbocharger is the risk of engine knock. When the turbocharger pumps air into the cylinder compressed air, and then further being compressed by the pistons in the cylinder. Why knocking occur is because, when air is compressed, the temperature increases, and the temperature may increase up to a point that’s enough to ignite the fuel before the spark plugs fire. To avoid knocking due to turbocharging, cars with turbochargers run on higher octane fuel. And in some engines, the compression ratio may have to be reduced if the boost pressure is really high.

Twin turbochargers

In most sport cars, the engines uses two turbochargers, one small turbocharger and a big turbocharger. The small one spins up to speed very fast to reduce turbo lag, and the big on takes up at higher engine speeds to provide more boost.

Intercooler

An intercooler or charge air cooler is an additional component that looks and works like a radiator, the intercooler is for cooling the intake air while a radiator is for the engine coolant fluid. The intake air passes through the inside of the sealed passageways inside the cooler, while cooler air from outside is blown through the fins of the cooler by the engine cooling fan.

The intercooler also helps improve the power by cooling the pressurized air coming from the compressor of the turbocharger before it enters the engine. This means when the cooler air entering the engine contains more air molecules than a hot air that has expanded.

Other importance of turbocharger

Another way a turbocharger helps is at high altitude where the atmospheric air is less dense. At high altitude, a normal engine will experience reduced power, because for each stroke of the piston, the engine gets a less amount of air molecules.

The turbocharged engine does not experience this because it compresses the intake air for power boost. A turbocharged engine may also experience a little reduction in power due to the low air density.

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