Twin Scroll Turbo Explained

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    Tundra Dweller
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    Twin Scroll Turbo Explained

    Post  on 2/2/2011, 8:21 am

    TWIN-SCROLL TURBOCHARGER AND GDI TECHNOLOGY

    Twin-scroll turbocharger designs have two exhaust gas inlets divided by split walls inside the turbine housing, with both gas passages controlled by a waste-gate. A twin-scroll turbo recovers even more energy from the exhaust than a single-scroll turbocharger thanks to a divided manifold. The twin-scroll design separates the cylinders whose exhaust gas pulses interfere with each other resulting in improved pressure distribution in the exhaust ports and a more efficient delivery of exhaust gas energy to the turbocharger's turbine.

    For example, at the start of the intake stroke of cylinder one, and when both the intake and exhaust valves of cylinder one are open (valve overlap period), cylinder three already starts its exhaust stroke with the exhaust valve open. If the exhaust passages of cylinder one and three were connected, the exhaust gas pulse from cylinder three would increase the back pressure of cylinder one. This would reduce the induction of the fresh air and increase the amount of hot residual gases inside the cylinder. However, with the twin-scroll turbocharger setup, this interference is minimized.

    The result of this superior scavenging effect from a twin-scroll design leads to better pressure distribution in the exhaust ports and a more efficient delivery of exhaust gas energy to the turbocharger's turbine. This in turn allows greater valve overlap, resulting in an improved quality and quantity of the air charge entering each cylinder. In fact, with more valve overlap, the scavenging effect of the exhaust flow can literally draw more air in on the intake side. At the same time, drawing out the last of the low-pressure exhaust gases help pack each cylinder with a denser and purer air charge. Maximum boost from the turbocharger is 17.4 psi.

    The twin-scroll turbocharger design has several other advantages over traditional, single-scroll turbocharging systems, including:
    Improved combustion efficiency
    Low engine-speed efficiency
    Kinetic exhaust gas energy is not wasted or trapped
    Cooler cylinder temperatures
    Lower exhaust temperatures
    Leaner air/fuel ratio

    * Better pressure distribution in the exhaust ports and more efficient delivery of exhaust gas energy to the turbocharger's turbine

    Essentially, Sonata's twin-scroll turbo directs even more air into the engine while a compressor increases the pressure entering the cylinder. This allows the air entering the cylinder to be even more densely packed for higher compression and better performance, contributing to a more-efficient burn and fuel efficiency.

    Two key features of Hyundai's twin-scroll turbocharger setup are:

    * The stainless steel exhaust manifold and the twin-scroll turbine housing are cast in a patent pending one-piece design
    * The waste-gate for the turbocharger uses a motor-driven electrical controller instead of being mechanically controlled

    Thanks to the integrated stainless-steel turbine housing with the exhaust manifold, not only is the weight and cost of the casting dramatically reduced, the durability of the turbine housing is also improved.

    By adapting the motor-driven electrical waste-gate, the boost pressure is precisely controlled. The back pressure is reduced when turbo boost is not necessary by opening the waste-gate, which improves fuel efficiency. In addition, during cold starts, the waste-gate remains open which results in faster catalyst light-off for reduced exhaust emissions.


    Giants4Ever
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    Re: Twin Scroll Turbo Explained

    Post  on 2/3/2011, 4:45 pm

    Tundra:
    That makes me want to go hug my Sonata! Good information, and it's really nice to know that we have cutting-edge engineering in this car. It shows.

    doeboy
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    Re: Twin Scroll Turbo Explained

    Post  on 10/23/2011, 6:54 am

    I just wrote a essay for college on turbochargers in automobiles. I really didn't go into the twin-scroll design because I was already almost past my word limit. It's good to know how this actually works as well. Good write up!


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    The Orillian
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    Twin Scroll Turbo Explained

    Post  on 7/13/2013, 10:30 am

    The one question I have left is how is the waste gate connected and is it internal or external? Good article!

    cj719
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    Re: Twin Scroll Turbo Explained

    Post  on 7/13/2013, 10:47 am

    internal


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    Robfrmny21
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    Re: Twin Scroll Turbo Explained

    Post  on 7/13/2013, 9:29 pm

    The waste gate motor is external but it's flapper controlled by a rod is Internal


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    2-0 Terror
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    Re: Twin Scroll Turbo Explained

    Post  on 7/14/2013, 8:07 am

    Is that from a Hyundai press release? I think a lot of it is overblown...no pun intended. They could have got more out of this setup, but they cheaped out in places.

    The Orillian
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    Twin Scroll Turbo Explained

    Post  on 7/14/2013, 10:57 am

    Thanks for the response. So I assume that the wastegate only controls one half of the twin scroll and when it is on full bypass the other half is still blowing on the turbine to give it the fast response? Also is the rod between the motor and flapper the cause of the so called 'rattling wastegate' that I keep reading about?

    Robfrmny21
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    Re: Twin Scroll Turbo Explained

    Post  on 7/14/2013, 11:33 am

    Yes the rod for the waste gate is the rattle


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    Miguel@UTUNE
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    Re: Twin Scroll Turbo Explained

    Post  on 7/19/2013, 4:52 pm

    Maximum boost from the turbocharger is 17.4 psi ?............. My last tune ran 23.5psi safety Razz


    Last edited by Miguel@UTUNE on 7/20/2013, 12:23 am; edited 1 time in total

    MDJammin
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    Re: Twin Scroll Turbo Explained

    Post  on 7/20/2013, 12:19 am

    The Orillian wrote:Thanks for the response. So I assume that the wastegate only controls one half of the twin scroll and when it is on full bypass the other half is still blowing on the turbine to give it the fast response?  Also is the rod between the motor and flapper the cause of the so called 'rattling wastegate' that I keep reading about?

    Actually its the rod on the ewg motor that rattles.

    And the twin scroll exhaust ports still meet at a single point. The WG bypasses both exhaust gas pulses. Its like two cars yeilding evenly into traffic. They all benefit by taking turns and drafting the car ahead of them.

    Its all in one place, but the timing of cyl exhaust is paired and fed through in alternating order.


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