Hey all, I am trying to understand the concept of the twin scroll turbo. Is a twin scroll turbo just a turbo that has divided inlets or what?
I am going to be putting a turbo in my car, and am looking into different set-ups and saw that garret has "twin scroll" turbos and was wondering if this was the same as our stock turbo's.

 

The "twin scroll" on the TII refers to an armature that actuated a block in the turbo manifold. The hot side of our turbos actually have 2 wheels with different clips. At low revs/boost, the exhaust is routed to the clip that spools the turbo faster (there is a better write up on this, I just dont know where it is). Then, when the revs/boost comes up, the arm moves the blockage out of the way and the exhaust is free to spool the scroll with the larger clip.

Did I confuse you yet?

 

um i took mine apart and it only had one wheel, actually several of them only had one. I thought it was simply two different tubes, with variying sizes, to increase the velocity of the gas. Either way, i removed that twin crap and the car ran much better.

 

It looked to me the that it's made to direct all of the exhaust on the tip of the wheel during low rpm, then switch to all exhaust over the entire wheel at higher rpm.

 

Yeah I read the mazda brochure(sp) on Aaron Cake's site, but wanted to be sure. I though it was also just describing two different sized inlets, one that would raise the pressure and get the turbine to spin faster and one that was larger and flowed more.
And I am wondering if anyone knows of a good site that will explain the different specs of a turbo (Airflow charts, pressure ratio charts, trim numbers, A/R numbers etc...)

Thanks

 

anyone else?

 

You've gotten a bit ahead of yourself.

What Jarrett has described in the twin-scroll control system fitted to S4 RX-7's. The turbo is of the twin-scroll design in that it has two seperate scrolls (paths) from the manifold to the turbine so that the exhaust gases are directed at the turbine from two different angles. Lots of other cars (including the S5) use twin-scroll turbos, although they were pretty new in 1986.

Mazda added the system described above to improve the turbo's low-end response. The larger scroll is blocked off until 2700rpm to spool it up quicker.

The S5's twin-scroll turbo doesn't have the control system that the S4 has because its divided exhaust manifold and electronic boost control provide the same benefit plus others.