twin chamber scroll? What is it?
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twin chamber scroll? What is it?
I've heard about twin chamber scroll, and how that's the type of turbochargers the TII's have. What is it, though? What does it do?
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A twin-scroll turbo has two seperate exhaust paths that aim the exhaust gases at the turbine wheel at two different angles. I don't know the exact science behind it, but it improves the turbo's responsiveness. Many modern turbo'd cars use twin-scroll turbos, but the FC was one of the first.
The S4 uses collected manifold that has a flap that can shut off one of the scrolls at low revs. This forces all of the engine's exhaust gases down one scroll, increasing it's velocity significantly and hence spinning the turbo up faster. At 2700rpm the flap opens and the manifold feeds both scrolls.
The S5 uses a fully divided manifold instead, so each rotor is dedicated to one scroll only.
The S4 uses collected manifold that has a flap that can shut off one of the scrolls at low revs. This forces all of the engine's exhaust gases down one scroll, increasing it's velocity significantly and hence spinning the turbo up faster. At 2700rpm the flap opens and the manifold feeds both scrolls.
The S5 uses a fully divided manifold instead, so each rotor is dedicated to one scroll only.
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Originally posted by Aaron Cake
...once you start to mod, the twin scroll becomes a restriction.
...once you start to mod, the twin scroll becomes a restriction.
#6
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probably not the best way to go about it though. The S5's didn't use it, and I really haven't heard of any other cars using a twin-scroll system.
My MR2 uses a similar system to the S5's, only instead of each rotor firing through a separate hole, Cylinders 1+4 fire through one, and Cylinders 2+3 fire through the other. I guess this is the "Twin Entry Turbo" system stamped on the intake manifold.
My MR2 uses a similar system to the S5's, only instead of each rotor firing through a separate hole, Cylinders 1+4 fire through one, and Cylinders 2+3 fire through the other. I guess this is the "Twin Entry Turbo" system stamped on the intake manifold.
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Originally posted by rotary>piston
The S5's didn't use it, and I really haven't heard of any other cars using a twin-scroll system.
The S5's didn't use it, and I really haven't heard of any other cars using a twin-scroll system.
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This is the description from the book RX8 by Jack Yamaguchi, p146.
"13B Independent Twin-scroll Turbo (1989-1991). A new turbocharger, called independent twin-scroll turbocharger, replaced the twin-scroll instrument. The new turbocharger retained two separate scroll areas, but minus a trap-door valve. Each of the independent scrolls received exhaust gas from one of the two rotor housings. Mazda's rotary engineers discovered that by completely separating the exhaust gas passages all the way to the turbocharger's entry area, no energy loss was incurred due to exhaut gas pressure interference between the two rotor chambers, thus exhaust gases would strike the turbine blades with more force."
"13B Independent Twin-scroll Turbo (1989-1991). A new turbocharger, called independent twin-scroll turbocharger, replaced the twin-scroll instrument. The new turbocharger retained two separate scroll areas, but minus a trap-door valve. Each of the independent scrolls received exhaust gas from one of the two rotor housings. Mazda's rotary engineers discovered that by completely separating the exhaust gas passages all the way to the turbocharger's entry area, no energy loss was incurred due to exhaut gas pressure interference between the two rotor chambers, thus exhaust gases would strike the turbine blades with more force."
Last edited by NoPistns; 08-29-03 at 09:22 PM.
#9
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Originally posted by NoPistns
This is the description from the book RX8 by Jack Yamaguchi, p146.
"13B Independent Twin-scroll Turbo (1989-1991). A new turbocharger, called independent twin-scroll turbocharger, replaced the twin-scroll instrument. The new turbocharger retained two separate scroll areas, but minus a trap-door valve. Each of the independent scrolls received exhaust gas from one of the two rotor housings. Mazda's rotary engineers discovered that by completely separating the exhaust gas passages all the way to the turbocharger's entry area, no energy loss was incurred due to exhaut gas pressure interference between the two rotor chambers, thus exhaust gases would strike the turbine blades with more force."
This is the description from the book RX8 by Jack Yamaguchi, p146.
"13B Independent Twin-scroll Turbo (1989-1991). A new turbocharger, called independent twin-scroll turbocharger, replaced the twin-scroll instrument. The new turbocharger retained two separate scroll areas, but minus a trap-door valve. Each of the independent scrolls received exhaust gas from one of the two rotor housings. Mazda's rotary engineers discovered that by completely separating the exhaust gas passages all the way to the turbocharger's entry area, no energy loss was incurred due to exhaut gas pressure interference between the two rotor chambers, thus exhaust gases would strike the turbine blades with more force."
The 87-88 twin scroll design was unique in that it had the flap that shut off one scroll at lower rpm's. Unfortunately, it didn't work as well as a conventional twin scroll design with a divided manifold, which Mazda used on the 89-91 cars.
#11
Originally posted by knightkarr
Is the "no-flap" design on the s5 responsible for the extra 14hp difference?
Is the "no-flap" design on the s5 responsible for the extra 14hp difference?
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Originally posted by 13bpower
Boost raised from 5.5 to 7.5
Boost raised from 5.5 to 7.5
Higher compression rotors
ighter rotors
Better intake
All up maybe it sounds like it could've been a bigger increase, but not much. The S5 might've had a slightly milder state of tune (fuel and ignition), so that there were improvements in economy and emissions as well as power.
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On the S4 system, when removing the rats nest, is it problematic to remove this system and the solenoid that goes with it, or should it be kept by some means? Not that it would be a major issue to keep, but I just want to get a bit of feedback as to what the actual, real world drawbacks and/or benefits would be to getting rid of the system...
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I plan to keep it when I remove the other solenoids (easy to do like you said), but if you want to know what it's like without it working simply unplug the solenoid and drive about for a while. The actuator will hold the flap open and you'll be able to decide if the increase in lag is acceptable to you.
Personally I feel it's pointless to remove the solenoid if you're not going to remove the flap too. It's like wiring NA aux ports open. Low-end losses, but no gains.
Personally I feel it's pointless to remove the solenoid if you're not going to remove the flap too. It's like wiring NA aux ports open. Low-end losses, but no gains.
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OK, so it keeps the port open without the solenoid...yeah, I guess it's worth keeping since I'm not yet up for pulling the exhaust mani and getting rid of the whole mechanism...
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