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. Hit that subscribe button.
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