Technique: 2-stage turbos

Posted on 06-07-2016 at 22:01 by MauritsH – 41 Comments”

The technique was especially used in heavy-duty diesel engines (trucks, etc), but the Bugatti Chiron is also equipped with it. It is high time the usefulness of 2-stage turbo’s from the cloths.

The larger the turbo, the higher the capital gains that these things can be achieved. A wise man learned that any advantage, its disadvantage and the same applies in this case. Larger turbos have more time to rinse. Once that happens, you can have the extra power there at one time full of in flips. If, at that moment just with a achterwielaandrijver in the middle of a bend, you have nice reflexes to the quantity of the catch. And indeed, this phenomenon is what is meant by turbo lag. More about that you can read HERE.

Installation of 2-stage turbo’s overcomes this problem by two turbos: one large and one small. As you know, a turbo powered by the exhaust gases of the engine. At low engine speed there simply less to exhaust gases from the manifold at high revs more. That also explains why a large turbo only at high revs that his work begins to do and why a small turbo understand useful is at lower speeds. In the case of 2-stage turbo’s work the large and the small turbo partly separately from each other, but they also work together. To explain this, a schematic representation of the system.

On the far right you can see the big turbo that only at higher speeds are allowed to play. On the left we find the small turbo. Furthermore, the bypass and the wastegate for this story of interest. We describe the effect of these components on the basis of three different situations, namely a low speed, medium speed and high speed.

Low speed

At the time that the motor is low speed and there is so (too) few exhaust gases from the manifold to the big turbo to be spinning, only the small turbo is used. In this situation, the wastegate and the bypass is closed, which means that all of the exhaust gases to the small turbo. That compresses and then to the air via an intercooler to the cylinder in, et voilà.

Medium speed

As soon as the engine speed increases, the wastegate is opening further and further. That means that the big turbo starts to play in the story. The large compressor is, however, not yet enough steam to do the work to take over completely. In this phase compresses the big turbo, however, the air, which is then further compressed by the small turbo. Below is the (two-phase compressed air to the cylinder in the hunted.

High speed

The task of the small turbo at high rpm, which means that all the work on the large turbo is left. To achieve this, the wastegate is fully open. All emissions are therefore in the direction of the large turbo led. Because of the small turbo in this situation does not play such an important role plays state of the valve in the bypass is fully open. The compressed air is therefore not more from the great first to the small turbo led, but goes instead directly through the intercooler to the cylinder.

Using this technique, manufacturers ensure that the power curve of the engine in question, a more linear gradient. That makes also lesser gods with a peace of mind from living in pk-guns as the Bugatti Chiron, but there are many more cars with 2-stage turbo’s. The first was (for passenger cars) for the BMW 535d (E60). The technique is applied especially in diesel engines, because which is generally less revs to make power on gas walk. Zelfontbranders have so much more benefit from a set of turbo’s at lower rpm helps to have the ability to boost.

Fotocredit: images per speed via Autozine.org, schematic view through BorgWarner