stock FC TII turbo twin scroll design

[yiug412]

Hi

I\'m planning to use a FC TII turbo onto my RB25DET engine as an slightly turbo upgrade, the stock RB one will break with only 1bar of boost. I did some research and came across this:

http://www.rx7club.com/showthread.php?p=1620878

Quote:
Jack K. Yamaguchi has this to say about the series 4 turbocharger: “The twin scroll turbocharger concept was developed jointly by Mazda’s Department Five and by Hitachi, and is manufactured by Hitachi having been designated HT18S-2S. It’s turbine-side bearing area is now water-cooled, and the main body is further protected by high temperatures by a dual-skinheat shield. The 1 blade turbine, of impact design, is 64 mm (2.52 inch) in diameter. It’s scroll area, the nry path for exhaust gas, is divided into two passages separated by an integrally cast wall; one, called the secondary scroll, has a trap-door-like gate operated by intake vacuum. The turbine thus has two cross sectional area (a) factors, A being the scroll’s smallest area as used in calculating turbocharger performance characteristics: 6.00 sq. cm (.93 sq. in) for the primary path and 9,48 sq. cm (1.47 sq. in) for the secondary. The other factor is R, the distance between the turbine-shaft center and the center of area A: 59.4 mm (2.34in) for the primary path, 60.4 mm (2.38in) for the secondary. Thus the twin-scroll turbocharger has two A/R ratios: 0.4 for the primary and 1.0 for the primary and secondary combined.”

As for the compressor side, “its 12-blade compressor is 63 mm (2.48 in) in diameter.

So where does the secondary scroll get the vacuum source from? didn\'t see any pipe going into the turbine nor a hole connecting the turbine to the compressor.

btw im still driving a rotary :driving

Louis

[m1tch]

Why would you want to put a series 4 twin scroll on the engine? It made around 180bhp, the series 5 non twin scroll was an improvement and brought the engine to 200bhp, it just has a flap top open and close the twin scroll. Surely it would just take a vac line off the intake to vacuum/boost?

[the hat]

Ideally you don\'t want too run a vacuum source too theactuator just a boost feed from
Before the throttle body I have no idea why it\'s just something I was always told it might be total
:censored::censored::censored::censored::censored::censored::censored::censored: for all I know

[Prof]

The turbine blades on the HT18S2 (Series 5 turbo II unit) have a shaped blad, so exhaust gases at lower pressure hit the turbine at a sharper angle.  As exhaust gas pressure increases, more of the exhaust hits the turbine blades at an angle.
 
Effectively they achieved the same thing as the twin scroll without the funky plumbing and fancy manifold.

[m1tch]

Ideally you don\'t want too run a vacuum source too theactuator just a boost feed from
Before the throttle body I have no idea why it\'s just something I was always told it might be total
:censored::censored::censored::censored::censored::censored::censored::censored: for all I know

There is a pressure drop between the turbo and the intake (which is why you see the psi drop on intercooler cores) so taking the vac souce from just before the throttle body will give an accurate measurement of exactly how much boost there is going into the engine, not the amount actually being produced.

[yiug412]

Taking the source before the throttle body is what u do for the turbo actuator as that means opening the actuator when the throttle is closed. Is that correct?

I wonder why i didnt see the twin scroll becuz i have the S5 turbine! Lol.

Its a hybrid making 300hp on rotary. So thats 400hp in piston?

Louis

[dthebuk]

Why would you want to put a series 4 twin scroll on the engine? It made around 180bhp, the series 5 non twin scroll was an improvement and brought the engine to 200bhp, it just has a flap top open and close the twin scroll. Surely it would just take a vac line off the intake to vacuum/boost?

Am I misssing something here? My old S5 Turbo looked like a twinscroll one to me

and Louis, surely the cost of getting a propper divided manifold made up for the rb is going to cost some silly monies? Is it really worth it when theres not much gain in pushing the boost up on an S5 turbo past 1 bar?
 
Though if you\'re doing it yourself/want a project its pretty cool :burnout

[yiug412]

Thats the same reason why i thot mine is twin scroll as well lol.

I have the knightsport one, so thats using a stock exhaust turbine and a uprated compressor.

I did plan to just ignore the metal in the middle and bolt it on XD

[m1tch]

The standard manifold for both series 4 and 5 are divided, the difference is the fact that the series 4 manifold is an active manifold.

Series 4 (with the actuator lever)




Series 5: