What do they mean by 'Twin Scroll Turbo'?

Virdi

Virdi

Virdi

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Hi all,

Lately - I've seen this term used a lot - 'Twin Scroll Turbo'

...what do they mean by this? How is it different to a normal turbo?

Thanks
 
Yeah, sounds like it:

Twin-Scroll Turbine Housing

Originally developed for commercial diesel applications,
turbochargers with a twin-scroll turbine housing have now been
successfully adapted for use with passenger car engines (both
gas and diesel). By utilizing dual openings, or volutes, into the
turbocharger's turbine housing, exhaust energy is optimized
which results in better engine performance at low speeds,
decreased backpressure at high speeds, and significant gains in
fuel economy.



Traditionally, passenger car turbochargers have had only one
volute through which exhaust gases leaving the engine cylinders
can enter the turbine housing (where they are used to create
torque). Unfortunately, this single entry design can sometimes
lead to combustion inefficiencies, since some cylinders are
expelling burnt gases while others are inhaling fresh air for
combustion. What happens is that the hot, dense exhaust gases
from the first set of cylinders are drawn into the second set of
cylinders, causing the combustion occurring in those second cyf
the fuel it's consuming.



Several wastegate solutions were considered to counter this
problem, with a twin-scroll design ultimately providing the best
solution. A twin-scroll, or twin-entry, housing allows each set of
cylinders to release its exhaust gases into a dedicated volute.
That way, it doesn't interfere with the other set of cylinders,
which is taking in fresh air at that same time. Of course,
refinements were necessary to account for the divider between
the two volutes, but thanks to the dedication of Garrett
engineers, those challenges have been met.

As this technology is further developed, even smaller passenger
car engines will be able to experience the benefits of the twin-
scroll turbine housing design including those fueled by natural
gas. And, as with all the products Garrett manufactures, twin-
entry turbocharger technology will continue to be developed with
an eye toward even greater efficiency and maximized performance.
Click to expand...

Won't that affect the Scooby engine/exhaust note? :(
 
Gilly said:
Yeah, sounds like it:

Won't that affect the Scooby engine/exhaust note? :(
Click to expand...

Yes, it does. A friend of mine recently changed from a P1 to a STI Spec C and the exhaust note is noticably different.

You get a lot more boost lower down as well but at the cost of losing it at the top of the rev range.
 
As noted, it basically means that you can 'pair' cylinders for more efficient scavenging and exhaust flow...

*n
 
GRT-TBO-039_450-1.jpg


A picture to demonstrate that its nothing too hi-tech :)
 
^^Gord^^ said:
Yes, it does. A friend of mine recently changed from a P1 to a STI Spec C and the exhaust note is noticably different.

You get a lot more boost lower down as well but at the cost of losing it at the top of the rev range.
Click to expand...

The exhaust note on the P1 is different to the Spec C because the P1 has unequal length headers and the Spec C has equal length (or more equal than the P1).
 
True but his P1 was far from standard and one of the this changes was equal length headers. The exhaust note is still very different taking this into account.
 
Jonny69 said:
:confused:

So why not just use a 4-2-1 manifold or is that just too damn obvious these days?
Click to expand...

That still doesnt seperate the cylinder pulses
loads of surface area - more heat loss + hotter engine bay
Larger volume = later boost response as the turbine works on a pressure ratio and a larger manifold needs more air to fill and reach pressure.
Heat cycling of tubular parts more likely to crack.
 
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