Twin Scoll / Divided Inlet Turbos

[Wez]

Hey All,

The question came up in another thread regarding twin scroll / divided inlet turbos, here is some info :-

What are twin scroll or divided inlet turbine housings? What are the benefits of using a twin scroll turbo?

A "twin scroll" or "divided inlet" means that there are two separate volutes within the turbine housing. The main reason for doing this is to isolate the pulses coming from each exhaust port and maintain more of the pulse energy from each cylinder all the way down to the turbine wheel. There are no differences between the turbine wheels used in open or single inlet turbines compared to those used in twin or divided inlet turbines.
Generally speaking, a divided inlet turbine setup will respond faster and produce boost quicker than single or open design of the same nozzle area, of course this is dependent upon proper execution. The simple fact that a divided housing is used does not guarantee these results.

While it does not cause any problems or harm to run a divided inlet turbine housing on a manifold that is an "open" design, none of the benefits of the twin inlet will be seen.

Maybe could be added to FAQ :innocent:

[sdavies]

Here here - in da faq kplzthx ;)

I have a twin scroll turbo with a non compliant manifold - guess I will see no benefits ;) Bummer! Cheers Amigo, excellent bit of info.

[Ian C]

I thought it was mainly of benefit to 4-cylinder engines?

Don't ask me why, something to do with the number of exhaust events or something.

-Ian

[bondango]

Fullrace done a good test recently on a 2JZ running with a gt4088r turbo. 1st test was using a standard non divided manifold and the second a divided. The results clearly showed a massive improvement in spool charctertisitcs using the divided manifold. They sent me an email with the results a few months back, il see if i can dig it out. Personally ive always stuck to a manifold to suit the turbo, be it a single or divided tang. As said pulse energy seems better applied on the twin scroll designs but is also effected by runner length, so the closer to an equal length manifold the better.

[Wez]

Here is my PHR Stage 1 twin scroll.

[~Rob~]

Is twin scroll another name for twin entry? for example, as on the MR2's?

[Alex]

Is twin scroll another name for twin entry? for example, as on the MR2's?

Nope,

Twin scroll or Divided Housing are the only 2 ways I would refer to it.

Twin Entry is not the same.

[bondango]

Is twin scroll another name for twin entry? for example, as on the MR2's?

Well on the early CT26 turbo's, such as those on the st165 Celica and mk3 Turbo, The exhaust housing on the manifold was non divided and also the Ct26 hotside was a sigle entrly (non divided).
The later spec ct26's found on the mr2 and st185/205 celica's used the newer design ct26 hotside which is a divided tang or to use the toyota coined phrase "twin entry"

[Chris Wilson]

The divided housings, on a correctly matched manifold, better utilise the exhaust pulses to spool the turbo below and around peak torque. Above that they show little difference. A none divided manifold with a divided turbine housing, and vice versa, will not work to take adavantage of the pulse tuning. It can be used on any engine with an equal number of cylinders and the correct manifold(s) and turbo (s)