whereiscarmensandiego

okay so removing the twin scroll is basically just taking out the flapper and filling the flapper arm hole? nohting else has to be done? i looked on fcs3pro and they had some greddy egr or somthing or other sensor on theres whats that

freemanrx7

You have to cap off the vac line that opens the twing scroll and also fill the small hole with something when you remove the flapper gate. Just do yourself a favor and buy an s5 turbo manifold and hotside.

totallimmortal

Sorry for the dumb question but what is different on the s5 hotside?

SpeedOfLife

iTrader: (16)

The S5 turbo doesn't have the twin scroll (S4 does), the turbo runners are the same shape and size (S4 turbo runners are not), and it uses a standard T4* flange (S4 does not).

*I think it's T4

RETed

Uh, no.

The Greddy EGT bung was added.

If you look carefully, there is an NPT plug that fills the hole the twin scroll flapper used to be.


-Ted

freemanrx7

The s5 hotside has 2 wastegate holes. It also bolts up to the straight through manifold (s5). The s4 has a small wastegate hole.

Try to search for some pics and you can clearly see the difrence. Also the s4 manifold lets the engine pulses hit eachother before touching the turbine blade.

lastphaseofthis

iTrader: (8)

anyone confirm this? i guess you couldn't just stick a larger turbo w/ a t4 flange because of the LIM clearances?

SpeedOfLife

iTrader: (16)

I just read somewhere else that it is a T4 flange. I'm sure the LIM has some to do with it, but I'm wondering if it's more so the coolant/oil lines since those sit even lower than the LIM. If the turbocharger is small enough I'm sure the stock S5 manifold could work, however when you go to all that work you might as well fab up a more efficient and prettier manifold.

initial D is REAL!

That flange is not a T4. It has one hole that is offset

I would also just considier going s5 by getting the manifold and turbo. Or you can just get the exhaust housing, if you can find somone to sell just that.

You might not even need to port the s5 turbo. I ported mine a little bit and it holds 12psi on a to4 hybrid

SpeedOfLife

iTrader: (16)

I was talking about the S5 flange.



It's not so much about 'not needing' the S5 turbo, the S5 turbo is simply more efficient and thus does not require the use of a twin scroll system. S5 turbocharger system = fewer parts to fail, barely less weight, and a little more efficient than the S4 turbo system.

RETed

NEITHER of the flanges are standard.
They are BOTH proprietary Mazda, and they do NOT match anything else out there.


-Ted

SpeedOfLife

iTrader: (16)

Well that sucks. Sorry.

initial D is REAL!

NP, its not really lighter either. Its just a totally better design. Some people would even call the s5 t2 a twin scroll. I dont want to get technical in twin scroll vs twin entry vs double entry vs twin entrance vs duel inlet vs sequestntial dual .... Basically its got twin entrance and 2 wastegate holes. They probably wont need any porting untill you go hybrid

I think what you got confused with is that the turbine is a t4 size or something. At least the guy at the turbo shop told me something like that. stock exhaust side is bigger than the intake compressor on these turbos

totallimmortal

What other differences are there between s5 and s4 turbos i thought the were both the same hitatchi unit with a different exhuast housing and the only other diff was the manifold

Boostmaniac

Hmm, I am moving over to an S5 unit myself.

Anyone know when a stock S4 turbo is supposed to hit boost? I don't see jack till 4k or higher, hence the move to the S5, but any answer to this question would be very helpful. Thanks.

initial D is REAL!

Do you mean peak boost, or anything above 0 on the gauge? its going to depend on your throttle position. Im not really looking at my rpm and boost gauge when i floor it, but it should hit boost pretty quick. I would get peak around 4K rpm wiht my to4 hybrid

SpeedOfLife

iTrader: (16)

I said lighter since it doesn't have a twin scroll actuator or related controls. You might only save 2.5lbs unless the turbo itself is heavier than the S4 turbo.

initial D is REAL!

What are the related controls you are talking about involved with twin scroll?

Its the same actuator. The only difference is the valve flapper has 2 valves, the housing has 2 holes, kind of like a lot of the factory jdm subaru turbos, mr2, and evo....

SpeedOfLife

iTrader: (16)

The S4 turbo has two actuators: wastegate and twin scroll. I was under the impression that the S5 turbo only has a wastegate actuator. The twin scroll actuator also requires a vacuum line, an electronic vacuum switch, and of course the wiring for that.

initial D is REAL!

Im getting confused here. The actuator is the thing with the vacuum line hooked up to it. That is an actuator to me

My setup is running off a megasquirt ecu, so I just have my vacuum line hooked up.
The factory might have an electronic switch, but you dont need it.

SpeedOfLife

iTrader: (16)

Yes, and the S4 turbo has two actuators. One controlling the wastegate and one controlling the twin-scroll flapper.

initial D is REAL!

where is the other one? In the manifold?

SpeedOfLife

iTrader: (16)

Precisely. The flapper, when closed, covers one of the turbo runners, thus increasing the air velocity over the blades. Once there is enough volume flowing it opens. I'm not exactly sure what that point is, but stock it is controlled via electric vacuum switch which is controlled by the ECU.

initial D is REAL!

Ahhh, yeah, when i bought my car it didnt have the factory manifold. Good to know. Every other twin entry setup didnt have that

Aaron Cake

iTrader: (1)

This topic is getting insane...

No 2nd gen RX-7 has ever had an industry standard turbo flange. Both the S4 and S5 are proprietary to Mazda.

Both series cars are twin scroll. The S5 accomplishes this with a fully divided manifold and a twin entry turbine housing. One scroll hits the turbine at a steep angle, the other is more standard.

The S4 has a similar twin entry turbine housing but uses a vacuum controlled valve to close off the 2nd scroll at low RPM. This maintains velocity through the first scroll, which hits the turbine hard and at a sharp angle. The flapper opens when more exhaust flow is present to allow flow to both scrolls.

The S4 twin scroll actuator is mounted on the manifold and connects via a rod to a crank. The crank is on a shaft that goes through the manifold and connects to the flapper door. The actuator looks a bit like the wastegate actuator but is much larger and more round. It is vacuum operated via a solenoid on the rats nest.

The wastegate actuator is mounted to the turbo compressor housing and connects to the wastegate in the turbine housing.

Removal of twin scroll is easy. With the whole assembly off the car, remove the actuator and then bash off the flapper with a hammer. Drill out the hole, tap to 1/2" and then plug with a bolt.