This is a discussion on 2011 wrx vs 2011 135i within the Comparison: WRX vs World forums, part of the Community - Meet other Enthusiasts category; Originally Posted by SPT2011 Yea, on paper the 135i and the wrx/sti are identical 0-60 and quarter mile times. But ...
Twin scroll is no turbo lag at all. Throughout entire rpm is steady compared to ours that kicks in at 4 grand or w/e. No disadvantages... If it wasent so expensive I guarantee most of us wrx and sti owners would own the 135i...
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Twin scroll does not necessarily imply no turbo lag. There are plenty of TS kits for Subarus that don't see full spool until 5K+Originally Posted by SPT2011
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There was a good thread around here that turned into a twin scroll information session. I don't remember it off of the top of my head.
Twin scroll's are more efficient generally speaking. This does not infer anything about their size relative (or 'spool' speed).
You may be thinking of a centrifugal supercharger, where the output is linear from the getgo... However, even though the output is linear, you actually will get a much slower 'spool' than a turbo or other forms of supercharging.
All forms of 'boost' have disadvantages, however, one way or another. The largest downside off hand of the twin scroll is the specific design requirements of the headers. Without headers designed specifically for twin scroll use, you'll lose most if not all of the advantages of the 'twin' scroll.
On the BMW note, normally if you saw a car worth 60k, and somebody was giving it away for 40k... It most certainly would sway some buyers. Tends to happen. At the same time, if a WRX or STi was sold for the price of a Honda SI, I am sure many SI owners would be swayed as well.
without twin scroll headers... your up pipe wont fit the twin scroll turbine outlet. Period. End of story.
Twin scroll turbos do spool faster... but they still do have lag. They're more efficient at putting that exhaust gas to use. Since our cars have exhaust "pulses" (that's why they have the boxer "rumble") there is some exhaust fighting (turbulence) in the R Manifold where the crosspipe connects. This disrupts some of the linearity of the exhaust, and creates additional un-needed back pressure. The twin scroll design eliminates this, and allows the alternating "pulses" to push the turbine wheel constantly. This creates better spool characteristics. It's a lot more complex than that... but that's just a little overview of why it spools better.
Ah very cool... I love to learn that kind of stuff, How much power are they putting to the wheels from the factory?