How twin turbo engine works

This article explains how a twin turbo engine works with the help of a video tutorial. In this article, we will not tell about how a turbocharger works. So if you don’t already know how turbochargers work, I’d recommend checking our article on the working on the turbocharger.

So how twin turbo engine works; In this article, we will be explaining two different setups.
1. Parallel twin turbo engine
2. Sequential twin turbo engine

Both of which are going to utilize the same size turbo. Just have two of them. But they’re going to use them in different ways. Now, there’s another type out there which uses different size turbos which I will explain in another article. So the first and the most simple setup to basically understand is parallel. Basically, all you’re doing is you have two separate turbochargers for two separate cylinder banks. So it’s almost like you’ve got two separate turbocharged engines. So here we’ve got a V6 engine. You can see the cylinder banks. You’ve got your two intakes, so here are your two turbochargers. Basically, during your exhaust stroke, you’re going to have exhaust come out through these exhaust manifolds.

How twin turbo engine works
How twin turbo engine works

Spin up the turbos, the turbos are going to pull in air, the air will go through the intercooler through the throttle to the intake manifold to the cylinders. Then repeat that process. So it’s just like with a regular turbocharger. The only difference is you’ve got two cylinder banks. So you split up the work between two turbochargers.
Things to note on parallel is that both turbos are always going to be active for the entire RPM range. Well, they may not, say you sized them so that they spool up at a higher RPM. But the point is they’re both always going to have exhaust flow directed towards them, and both turbos are the same size as.

Now another type of Turbo setup is sequential. So here we’ve got a four-cylinder engine. Mainly what happens here is, you have one turbo active at low RPM and then both turbos active at a higher RPM. When you have more exhaust flow. So at low RPM, you’ve only got a single turbo active, and here we have a bypass valve. This is basically what shuts off this turbo. So if air isn’t allowed to pass through here. It’s not going to be able to spool up, and it’s not going to be able to put any boost through this piping. What happens is, after your exhaust stroke, all your exhaust is going to be directed to this turbo here.

So it’s going to spool up this turbo, and then it’s going to pull in air through this intake along this channel. It’ll send that air up here into the intercooler through your throttle into your intake manifold. Then into your engine and then, It’ll just keep recirculating like that along. Then, of course, out the exhaust here as shown in the video.

Now, why would you only have one turbo spooling at low RPM?

Well, the reason is, you don’t have that much exhaust so you couldn’t spool up both of these turbos with the limited amount of exhaust. That’s why you are sending all of it to one turbo. That’s enough to spool it up and create a boost for the engine. Now at higher RPM scenarios, this bypass valve is going to open up. You’re going to have a lot more exhaust, and so all of that exhaust is going to be directed to both of these turbos. So they’ll both be pulling in air, bringing it to the intercooler through the engine and then they’ll continue spooling out both of these turbos. This then finally out the exhaust. So basically the reason you can do that is that you have more exhaust flow. Once again, both of these turbos are the same size.

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