Phil Explains Things: Turbocharging

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The word "Turbo" has been thrown around since the 1980's as a way to explain that things were Better than the normal item. Things like Personal Computers had a "Turbo" button.
Seriously....a turbo mode on the computer.
But what exactly is a Turbocharger, what does it do, and how does it do it? To understand it, we need to know why they exist. As you gain altitude, the air becomes thinner, which caused carbureted engines to run rich due to the decreased oxygen content, and therefore lose power. According to E3 spark Plugs, the engine loses power as the altitude increases. They state that the equation is:

HP Loss = (elevation x 0.03 x horsepower @ sea level)/1000

So, to fix this, early 1900's engineers fit Turbochargers or Superchargers (which will be discussed in a future post) to the aircraft engines of fighter planes to both increase their speed, and enable them to fly higher without losing power.

What is a turbocharger? A turbocharger is an air pump powered by an exhaust-driven turbine, which forces air into the intake manifold.
This Turbocharged engine shows all of the components of a Turbocharging system. The hot exhaust gasses exiting the cylinder head into the hot side of the turbo (The darker-colored portion of the turbo), also called the Turbine. It enters at the edge of the turbo, forcing it to spin. The faster the exhaust gasses flow, the faster the turbine spins. Hot exhaust gas exits via the center of the turbine section, which are then carried out the tailpipe. The Wastegate, which may be internally mounted in the turbine housing, or externally, in the exhaust manifold, enables the exhaust gas to bypass the turbine when boost is not needed.

On the intake side, the air enters at the cone filter (shown in red here), and gets sucked in by the compressor (the lighter-colored section of the turbo, as indicated by the "Turbo" label.) The compressor wheel, driven by a shaft connected to the Turbine wheel, pulls intake air into the center and out off of the edge of the wheel, much like a hair dryer. Due to the nature and location of the Turbocharger, the now-compressed air exiting the turbo is quite warm. So, the air charge travels through a box called an Intercooler, which uses air traveling past it, usually placed in front of the radiator, to cool down the air charge. From there, it runs through plumbing into the Intake manifold. On the way there, though, it runs past another valve. Often referred to as either a Bypass Valve or Blowoff Valve, this valve prevents engine runaway or overboosting by releasing air charge either into atmosphere or recirculating it back into the turbo inlet.

All of this equates to a  potentially higher power output, better high-altitude performance, and, in some cases, improved fuel economy. To learn more, check out the Wikipedia post.
(photo credit)
 Turbos have revolutionized the motorsports world. Before turbos, guys who raced cars repeated their mantra of "No replacement for Displacement", meaning the only way to make big power is to have the highest displacement V8 possible. Even so much as adding giant superchargers to their engines. But when Turbos became popular on smaller engines, we started seeing power levels closer to what the V8's were making. It's not uncommon to see a Toyota Supra engine (3.0L Dual-Overhead-Cam Turbo inline 6) making upwards of 1,500hp. And, with a bit of work, Mitsubishi's venerable 4G63T can make 900+ hp.

That was just a quick rundown of how turbos work and what they do.
Keep checking back for more car knowledge.



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