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  • It means power, speed and...

  • (imitates engine)

  • (electronic music)

  • To understand turbos,

  • you have to know the basics of how an engine works.

  • Think of an engine like a very large pump.

  • It sucks air and fuel into a cylinder,

  • compresses and combusts it before pumping

  • out all the goodies that people like to get angry about.

  • (coughs)

  • To get more power from an engine,

  • we need to burn more fuel, more quickly.

  • Getting fuel is usually as simple as turning the tap up,

  • but unless there's also more air,

  • that extra fuel is useless.

  • A cylinder is limited in how much air it can breath,

  • by it's size or displacement.

  • Historically, when engine makers wanted

  • more air to mix with their fuel,

  • they needed a bigger cylinder.

  • There was no replacement for displacement.

  • This made engines larger, heavier,

  • and often times slower to rev.

  • Then in 1905, a Swiss engineer named Alfred Buchi,

  • came up with a replacement for displacement,

  • when he used the exhaust gasses of an engine,

  • to power a compressor that then fed

  • denser air into the combustion chamber.

  • More air, meant more fuel could burn, and get more boom.

  • Turbos were quickly adopted by the aeronautical industry.

  • When you're 20,000 feet up, the air is almost half as dense,

  • and engines would lose as much as half of their power.

  • - [Narrator] 400 horsepower at sea level.

  • But moving up to 14,000 feet, it drops to 265.

  • - A turbo restored air pressure in the engine,

  • back to sea level pressure.

  • This is called turbo normalizing.

  • When a turbo is used to exceed that pressure,

  • that's called turbo charging.

  • So how does all this crap work?

  • This is a turbo.

  • As your engine expels exhaust gasses, they enter in here.

  • The exhaust air gets piped over this turbine,

  • and spins it like a pinwheel.

  • Now we're done with the exhaust,

  • and it gets shot out the back of your car.

  • The turbine is connected to this impeller,

  • on the other side of the turbo.

  • And it spins too.

  • As it spins, it sucks in a ton of air through this inlet,

  • and shoots it out this outlet into your intake manifold.

  • The air is now more dense, so it has more oxygen,

  • so it can burn more gas more quickly,

  • giving you more power.

  • To keep that charged air from going back into the turbo,

  • when you lift off the throttle,

  • a blow off valve relieves the pressure,

  • by letting the air go back into the atmosphere.

  • That's why you get that cool...

  • (imitating valve release)

  • - I like V8s.

  • (laughing)

  • - Turbo charging creates a lot of heat.

  • The turbine side constantly has

  • blazing exhaust gasses passing through it,

  • making it literally burn red hot.

  • You may have noticed that this side,

  • which is appropriately referred to

  • as the hot side of a turbo, often looks rusty.

  • That's because the extreme heat acts as a catalyst,

  • causing the metal to oxidize more quickly.

  • This side, also generates heat.

  • When you compress air,

  • you push the molecules closer together, and create friction,

  • when they all rub up against each other.

  • All these hot energized molecules,

  • they move around everywhere, and then they increase

  • the speed of the air, and that makes them lose density.

  • The whole point of forced induction

  • is to get denser air, right?

  • Well if we cool all of this hot turbo charged air off,

  • the molecules will cool down,

  • sit closer together and become even more dense.

  • There are a few ways to do this.

  • The most popular and simple way, is with an intercooler.

  • An intercooler sits between the turbo and the engine.

  • The air passes through channels with cooling fins.

  • The cool air from outside passes over the fins,

  • absorbs the heat, and reduces the temperature.

  • And if your Suburu's got a hole in the hood,

  • don't worry, that's for your intercooler.

  • (slow piano music)

  • So, now we know that a turbo charger is an air compressor.

  • So if you want more power,

  • why not just get the biggest turbo you can find?

  • Well it's not that easy.

  • If a turbo's too big it takes a long time

  • for the exhaust to get it spinning fast enough,

  • to compress the air.

  • The time between hitting the gas,

  • and feeling the boost, is called lag.

  • Engineers solved this problem by using two smaller turbos,

  • to push more air than one large one.

  • While we think of twin turbos as a their own category,

  • there's actually multiple ways to put two turbo chargers,

  • on an engine.

  • Parallel turbo charging,

  • sequential turbo charging,

  • and to a lesser extent, two stage turbo charging.

  • The first commercially available twin turbo car,

  • to put these ideas to the test,

  • was the Maserati Biturbo sold in 1981.

  • This first production attempt at twin turbo charging,

  • used the simplest method of applying

  • two turbos to an engine.

  • Parallel turbocharging.

  • As long as there's enough space in the engine bay,

  • using two turbos is actually easier than using one,

  • when an engine has two banks of cylinders,

  • such as a V shaped engine.

  • Each bank can have its own turbo,

  • rather than routing all of the cylinders into a single one.

  • Achieving the proper power balance between the two banks,

  • proved to be a challenge.

  • In early twin turbo cars like the Nissan 300ZX,

  • and Mitsubishi 3000GT,

  • designers found, that the easiest way to get it right,

  • was to have each turbo feed the opposite cylinder bank,

  • instead of the one it was closest to.

  • This formed a healthy feedback loop that automatically

  • balanced the power between the two banks.

  • Crossing the V solved one problem,

  • but it created another one.

  • The turbos would spool quickly, but now the charged air,

  • had to travel further before it reached the engine,

  • creating a new kind of lag.

  • Dang, just when you think you got it!

  • If only there was a way to have

  • the quick spool time of a small turbo,

  • the power of a big one, and get that air

  • to the dang engine toot sweet.

  • (phone rings)

  • Yes?

  • - What about sequential turbo chargers?

  • - Sequential turbos, thanks James.

  • I'll see you tomorrow at work?

  • Why not?

  • Well parallel turbo charging,

  • uses two equally sized turbos, working 100% of the time.

  • Sequential systems use a little turbo

  • that spools up quickly to tide you over,

  • until another larger turbo, has time to spool up.

  • This method alleviates turbo lag,

  • and provides a much smoother power gain.

  • To control the flow of exhaust to the correct turbo

  • at the right rev range, a series of bypass valves

  • opens and closes at just the right moment,

  • ensuring the proper turbo is getting spooled

  • at the proper time.

  • Both the Mark 4 Supra, and FDRX7,

  • use sequential twin turbo systems.

  • Those cars ruled the 90s.

  • Just like me dude.

  • (rhythmic music)

  • Turbo charging,

  • is the perfect example of performance technology,

  • trickling down to the rest of the market.

  • The 80s and 90s paved the way for modern turbo charging.

  • And now, almost anything can come with a turbo.

  • And that means, sometimes normal drivers,

  • can have a little fun when they want to.

  • Do you like videos about air and gas?

  • Check out this other episode on combustion.

  • Or check out Pumphrey's new car show,

  • where he drives the Mazda sparkless petrol engine prototype.