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Discussion Starter · #1 ·
So I'm trying to settle a debate on whether they're is a substantial benefit to a twin scroll housing and manifold vs single. Specifically I'm building a 160ci I6 and while going over a the build with a friend who has a similar build the question of the twin scroll really is a benefit. His engine is built the same way but has an 80mm single scroll with an unequal length manifold and he doesn't get into meaningful boost til 6700ish rpm. I made the comment that I hoped to improve that spool a good bit with my billet wheeled 76mm twin scroll with an equal length manifold. He is of the opinion that 90% of any improved spool would be due to the billet wheel and not much from the twin scroll and further that whatever spool improvement I see is at the larger loss of top end power.

Now our comparison isn't exact due to the different sized turbo so I don't necessarily want to use that comparison just say everything else was equal except the manifold design and turbo housing. Would you see a significant improvement in spool without giving up much(if at all) max boost? In my mind(uneducated as it is) the twin scroll isn't better because it in effect makes the turbine housing smaller as my friend seems to think but rather it makes more efficient use of the exhaust pulses to accelerate the turbine quicker while not sacrificing much flow. Particularly in our small engines with larger turbos we seem to max out the compressor side before running into big BP issues. I searched but haven't seen any concrete evidence like back to back tests show proof one way or the other.

Another thing that makes me think it does make a difference is for example my DD is a TTV8 which the exhaust and intake flow is reversed so the exhaust is in the V. On the sportier version the exhaust manifold crosses between banks pairing the turbos with the right cylinders to have continuous pulses vs on mine which each bank feeds a turbo so they receive intermittent pulses and use a divided V band housing. IMO an oem is going through that trouble(and patenting the manifold design) if there isn't a big difference. What say you experts?
 

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Borg Warner engineer told me the twin scroll stuff from them can be worth up to 15% better response and power through the midrange and down 2-3 at the very top of the curve.
 

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Discussion Starter · #3 ·
Borg Warner engineer told me the twin scroll stuff from them can be worth up to 15% better response and power through the midrange and down 2-3 at the very top of the curve.
Yeah that sounds like something I could believe and pretty much what I'm hoping for. Not 100% sure that the equal length manifold is that big a deal but glad to hear it cause I'm hoping to improve spool vs his by about 500-600rpms.
 

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My thoughts.... And thanks for clearing that up John.

Ive always felt like this...

Borg warner in all their infinete wisdom, they put that their for a reason, and im not to ashamed to say, they are far smarter then I.

SO. With that, i would :)
 
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