Trucks 101: How a Turbo Works May 31, 2015

How do you make a car or truck faster without making the engine larger? Well, over the years this question has been answered in a variety of ways. Carburetors were replaced with fuel injection, clearances inside of engines were reduced, and better oils were conceived. While all of these are great ways to get more out of less, nothing has been better than the tried and true turbocharger to add power and speed without hurting weight or fuel economy.

While this is all nice and well, turbos don’t work by black magic or wishful thinking, they use some basic mechanical functionality and some expert machining to make an engine work better than it ever could by itself. So, how exactly does a turbocharger work?

How Engines Work

Before getting into how a turbo works, it’s a good idea to know the basics on how an engine works. If you’re already familiar with this, feel free to skip to the next section. The engine in your car or truck is what’s known as an internal combustion engine. As their name suggests, they use combustion inside of the engine itself to create the energy required to get you moving. Gasoline-powered cars and trucks use spark plugs to create the combustion while diesels use heat and pressure to make combustion happen. Either way, engines work by pulling fresh air in, adding fuel to the mix, combusting this mixture, and expelling the exhaust.

This four stroke cycle is done thousands of time per minute (RPMs), and the end result is power to the wheels. Typically, to get more power you would have to increase the size of the engine, usually measured in liters, by increasing the number of cylinders that the combustion can take place in. This is why non-turbo gasoline cars and trucks are often V6 or V8, referring to the layout and number of cylinders. A V6 has six cylinders (and pistons) laid out with three on each side in a V formation. Cars and trucks with a turbocharger installed use smaller engines to benefit from the increased power while keeping engine size and fuel economy small.

How Turbochargers Work

So, with a basic understanding of how engines work under our belts, it’s time to see how a turbocharger works. Simply put, a turbocharger uses the exhaust that’s already coming out of your engine from the four stroke process to turn an impeller that’s used to forcibly pull fresh air into the system. More often than not, the biggest limiting factor to getting more power from an engine is how well air can be brought into it. This is why cold air intakes and performance air filters exist. The turbo pulls air in and forcibly pushes it into the engine. Here, it’s mixed with fuel and combusted.

Think of a turbo like someone stoking a fire. Sure, a fire will burn fine on its own, but if you blow on it, or if the wind blows on it, the fire will grow exponentially as fresh oxygen is brought into the mix.

The added oxygen helps the engine burn fuel more efficiently, fiving you more bang for your buck. If you were to pull a turbo apart you would see that at its core there are two blades. One is spun by the exhaust before it gets sent through your exhaust system, and the other, which is spun by the first blade, pulls air in. It’s this method that makes turbocharges so amazing. By using the byproduct of running an engine you can add more power right back into it. In short, an automotive turbo works like an air compressor that doesn’t need external power to work.

First, cool air enters the engine’s air intake. Instead of going straight to the engine it first passes through the turbo. Next, the compressor’s fan pulls the air in far faster than it could go normally, squeezing and compressing the incoming air. From here the air, which is now hot from being compressed, passes through a heat exchanger to cool off a little bit. Remember, cold air is more dense than warm air, so it has even more to offer. The cooled, compressed air enters the cylinder and the four-stroke process happens. As the cycle finishes up it creates exhaust gas, which is circulated past the impeller of the turbo, creating the vacuum on the other side, pulling in more air to be compressed and the process starts all over again.

What This Means For Your Vehicle

So, what does this all mean? Well, using a turbo diesel engine as an example, each stroke of the engine now has more oxygen in it, which means the fuel/air mixture is easier to ignite and when ignited, burns hotter. This means more power with the same amount of engine work and less wasted fuel. It also means less waste in the environment since there’s less unburnt fuel leaving the tailpipe.

While this is all nice and well, turbos also mean more power from the same engine. By cranking up the pressure the turbo allows into the engine you can increase your power significantly.

There’s lots more involved in a turbo including a wastegate that regulates your turbo pressure and a blow off valve that releases said pressure to the atmosphere, but that’s far more than we can cover here. For now, understanding this basic functionality can help you know what’s going on under your hood.

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