Twin scroll....

[Grrrrrrr!]

Since we have a bit of a blitz on turbo tech going on..

While googling about the TD05h turbo that Lith recommended in the other thread I came across something I found interesting..

Twin-scroll, twin entry and divided housing... I thought they all meant the same thing, and the general idea was that by splitting the pulses from certain cylinders into the correct port of the turbo (eg 1&4, 2&3 on a four banger) you could harvest more of the pulse energy to spool the turbo a bit faster.

but, I came across a couple of forums where people were arguing they are different things. One of the theories was that twin scroll meant two different sized volutes, and the exhaust was directed to the smaller one to spool it up faster then the exhaust went to both/the larger (opinions seemed to vary).

I have seen a quick spool valve thing advertised on the tard that appeared to be designed to be used for the above reason.

So what gives, is this twin scroll thing as described as above, or is somebody hitting the peace pipe a bit too hard?

[loudstealthGT-Four]

Twin-scroll or divided turbochargers have two exhaust gas inlets and two nozzles, a smaller sharper angled one for quick response and a larger less angled one for peak performance.

Straight from the God of knowledge

[Grrrrrrr!]

And yet, the only reference used in that paragraph (http://www.modified.com/tech/modp-0906-twin-scroll-turbo-system-design/full-race.html) mentions nothing at all about a large and a small, it talks entirely about pulse separation.

Also makes no sense to have a large and small without a valve, since it would mean half your cylinders would be restricted while the other half were breathing freely.

The other thing that makes me think this is all BS, is that i've never seen a twin-scroll turbo spec sheet point out which is the small and which is the large...

Also http://www.autozine.org/technical_school/engine/Forced_Induction_4.html quite interesting about the twin twin-scroll cross bank turbo configuration on the BMW. Oh yeah, and again, pulse separation.

I'm calling it, the different (flow) volutes is a complete load of BS. They do appear to be different sizes, but I bet there is some funky aero reason for it and they actually flow the same.

[Lloyd]

Go to google. Click images. Search for "twin scroll" and look at the pictures.

[Grrrrrrr!]

As above, i'm betting its something to do with the bigger runner being partially blocked by the flow from the other runner and the end result being the same flow.

[Crucible]

Have a look on the Garrett site also, lots of good reading there.

[Lith]

Yep your conclusion is on the money with my understanding on the world. It's generally considered or expected to be equal flow, though no doubt there will be exceptions to the theory. Remember anyone can edit Wiki articles, just because it says something doesn't mean it is true.

Here's some info on twin scroll vs single scroll goodness from some time ago on this forum:
http://forums.toyspeed.org.nz/viewtopic.php?p=709185#709185

[Mr Ree]

Remember anyone can edit Wiki articles, just because it says something doesn't mean it is true.

And never a truer word was spoken.

[gt4dude]

Theres no evidence of a larger port on a ct26. Just 2 small ports