MastrChase

Guys I'm working on a TII swap into my 86 and the engine I'm looking at says it comes with...

"with the ported wastegate and twin scroll in locked position. That way with an upgraded exhaust you can control boost creep better"

...I really don't know much at all about turbos, and this seems to throw most of my friends off. Any ideas? Is he talking about the wastegate? Would a boost controller be better?

Thanks for any info.

(yes I searched, lol)

RotaryRocket88

iTrader: (7)

S4 TII engines have a twin scroll actuator that opens/closes a flap over one of the turbine runners. It closes off under 2700 RPM to increase exhaust velocity & spool the turbo quicker. I would assume that the "locked position" means that they wired it permanently open. It's not going to affect boost control; that's the wastegate's job. On a related note: port the wastegate huge.

MastrChase

So... is the twin scroll locked open a good thing or a bad thing? The ported wastegate is good, got it. Lol.

Thank you SO much. I really appreciate the reply.

RXSpeed16

iTrader: (41)

Locking it open only disables the system without removing the restriction caused by the mechanism in the exhaust manifold. The turbo will lose some response and feel like it has more lag, without gaining any power. So you're basically making it less fun to drive for no gain.
In your application, it sounds like it has been disabled in an attempt to prevent boost spikes around the transition RPM. However, as RotaryRocket88 stated above, the wastegate controls boost pressure and creep (if it's big enough). I've never seen a boost spike due to the twin scroll but I imagine it could be possible if it's out of adjustment. Most likely the actuator was removed because it was in the way and the arm is wired in a 'locked position'.

And on a side note, a boost controller will never lower the boost pressure.