Twin Scroll Turbo on 2.0 Sti or 2.5l Turbo Sti ?
01-15-2003, 03:52 PM
#1
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Twin Scroll Turbo on 2.0 Sti or 2.5l Turbo Sti ?
I just wanted to ask around to see if you guys rather have the 2.5l turbo or the 2.0l with the twinscroll job. From what I have looked at from the Garret turbomachinery website, the Twin scroll is a sort of "variable-turbo" system. If I have understood it correctly, it would match great with engines that don't have much low end output (like the 2.0l in Japan). The 2.5l turbo is announced here and the twin scroll turbo is gone. Is this the sole reason for the regular turbo?
I'm sorta studying more about engine "engineering" after learning about turbomachinery in a college class that I just took a year ago and wanted to see if there was anybody who understood the differences btween the two types of turbo systems.
Thx,
Tim
I'm sorta studying more about engine "engineering" after learning about turbomachinery in a college class that I just took a year ago and wanted to see if there was anybody who understood the differences btween the two types of turbo systems.
Thx,
Tim
01-15-2003, 08:29 PM
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I'd say at this stage the 2.5 will be a bit of a low-tech engine compared to the 2 litre. I believe one of the reasons FHI went to the 2.5 for the American market was for emissions compliance. I doubt you will see features such as semi-closed decks which make an engine more conducive to more hypo mods. Another thing to remember is the rally homolgation side of things. You'll find most of the high tech stuff in the 2 litre so they can run them in the rally cars and whip those Evos. Now that Subaru have fixed to very weak gearbox which was in the GC8 WRX you'll find many more competitors running serious Group N cars in the WRC.
01-15-2003, 09:23 PM
#3
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Well thats a good guess, as it's what I would have bet subaru was going to do with the USDM STi, but it turns out that were getting the best powerplant to find its way into an imprezza yet.
(This is straight of of subarus official US website btw)
Low tech, weak tranny? Haha! Best STi anywhere, finally the US gets the long end of the stick!!!
read more at
http://impreza.subaru.com/microsites...sti/wrxsti.jsp
Some specs:
For the record thats 20 more hp and torque than the rest of the world gets. Booyah grandma!
(This is straight of of subarus official US website btw)
ENGINE/TRANSMISSION
A unique engine deserves a unique transmission
The Impreza WRX STi draws motorsports technology directly from Subaru expertise in World Rally Championship (WRC) competition, and is designed to appeal to the serious driving enthusiast. Impreza WRX STi is powered by a turbocharged and intercooled 2.5-liter DOHC boxer teamed exclusively to a short-throw, close ratio six-speed manual transmission.
The 2.5-liter horizontally opposed ("boxer") four-cylinder engine is based on a specially reinforced "semi-closed deck" engine block with forged aluminum alloy pistons, forged high-carbon steel connecting rods and sodium filled exhaust valves. This advanced powerplant incorporates Subaru AVCS (Active Valve Control System) variable valve timing technology to optimize the engine's volumetric efficiency throughout the rev band. This is the first application of this technology on a Subaru in North America. The large capacity intercooler includes a manually operated water spray feature to provide additional cooling.
A unique engine deserves a unique transmission
The Impreza WRX STi draws motorsports technology directly from Subaru expertise in World Rally Championship (WRC) competition, and is designed to appeal to the serious driving enthusiast. Impreza WRX STi is powered by a turbocharged and intercooled 2.5-liter DOHC boxer teamed exclusively to a short-throw, close ratio six-speed manual transmission.
The 2.5-liter horizontally opposed ("boxer") four-cylinder engine is based on a specially reinforced "semi-closed deck" engine block with forged aluminum alloy pistons, forged high-carbon steel connecting rods and sodium filled exhaust valves. This advanced powerplant incorporates Subaru AVCS (Active Valve Control System) variable valve timing technology to optimize the engine's volumetric efficiency throughout the rev band. This is the first application of this technology on a Subaru in North America. The large capacity intercooler includes a manually operated water spray feature to provide additional cooling.
read more at
http://impreza.subaru.com/microsites...sti/wrxsti.jsp
Some specs:
300-horsepower @ 6,000 rpm, 300 lb.-ft. of torque @ 4,000 rpm
2.5-liter intercooled and turbocharged 4-cylinder boxer engine with Active Valve Control System (AVCS)
Full-time All-Wheel Drive (AWD) with Driver Controlled Center Differential (DCCD)
Mechanical limited-slip rear differential
Suretrac viscous limited slip front differential
4-wheel fully independent sport-tuned suspension with inverted struts
6-speed manual transmission with short-throw shifter
2.5-liter intercooled and turbocharged 4-cylinder boxer engine with Active Valve Control System (AVCS)
Full-time All-Wheel Drive (AWD) with Driver Controlled Center Differential (DCCD)
Mechanical limited-slip rear differential
Suretrac viscous limited slip front differential
4-wheel fully independent sport-tuned suspension with inverted struts
6-speed manual transmission with short-throw shifter
Last edited by Br1t1shguy; 01-15-2003 at 09:25 PM.
01-15-2003, 10:07 PM
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The point I was trying to get across is that I think the 2.5 is a much lower stressed unit compared to the 2.0. I accept that I made a mistake about closed decks etc. I haven't completely read up about USDM model. Also, we've had the same six speed box available in both the WRX and WRX STi since MY01. Does anyone know what boost, compression ratio and redline rpm of the 2.5 motor is? Here in AU, WRX motor was upped to 9.0:1 compression ratio and this along with AVCS has made the motor heaps motor drivable and is now finally on par with the old GC8 WRXs performance wise. We expect to get the new MY03 STi in February.
MY02 STi 2.0 VF34 (Bug Eye)
206kw = 275hp = 138hp per litre
8.0:1 Compression Ratio
MY03 WRX 2.0 TD04 (New Shape)
168kw = 225hp = 112hp per litre
9.0:1 Compression Ratio
MY03 STi 2.0 Twin Scroll TD05(New shape)
220kw = 294hp = 147hp per litre
9.0:1 Compression Ratio
USDM MY04 STi 2.5
224kw = 300hp = 120hp per litre
?? Compression Ratio
MY02 STi 2.0 VF34 (Bug Eye)
206kw = 275hp = 138hp per litre
8.0:1 Compression Ratio
MY03 WRX 2.0 TD04 (New Shape)
168kw = 225hp = 112hp per litre
9.0:1 Compression Ratio
MY03 STi 2.0 Twin Scroll TD05(New shape)
220kw = 294hp = 147hp per litre
9.0:1 Compression Ratio
USDM MY04 STi 2.5
224kw = 300hp = 120hp per litre
?? Compression Ratio
01-15-2003, 10:16 PM
#5
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Car Info: 2005 STi, 2005 OXT
Originally posted by Jonno
USDM MY04 STi 2.5
224kw = 300hp = 120hp per litre
?? Compression Ratio
USDM MY04 STi 2.5
224kw = 300hp = 120hp per litre
?? Compression Ratio
According to http://www.subaru.net (a dealer's website, but nonetheless, very very cool), 8.2:1 is our STi's CR.
I'm willing to bet that the US STi runs lower boost and has a broader torque band than the Australian 2.0 TD05 twin-scroll setup.
Twin-scroll is basically used to get faster boost response. It will help with low end and midrange power, mostly. The 25% greater displacement will do the same for the US version.
Joel
01-16-2003, 02:08 PM
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Originally posted by Joel Gat
Hello,
According to http://www.subaru.net (a dealer's website, but nonetheless, very very cool), 8.2:1 is our STi's CR.
I'm willing to bet that the US STi runs lower boost and has a broader torque band than the Australian 2.0 TD05 twin-scroll setup.
Twin-scroll is basically used to get faster boost response. It will help with low end and midrange power, mostly. The 25% greater displacement will do the same for the US version.
Joel
Hello,
According to http://www.subaru.net (a dealer's website, but nonetheless, very very cool), 8.2:1 is our STi's CR.
I'm willing to bet that the US STi runs lower boost and has a broader torque band than the Australian 2.0 TD05 twin-scroll setup.
Twin-scroll is basically used to get faster boost response. It will help with low end and midrange power, mostly. The 25% greater displacement will do the same for the US version.
Joel
Tim
01-16-2003, 02:20 PM
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Car Info: 2005 STi, 2005 OXT
Hello,
Tim, an answer to that question would be even more purely speculative. Variable cam timing allows you to run the necessary overlap at low end, off-boost, for good efficiency without hurting emissions, while still reducing overlap at the top end, where higher boost is likely, which reduces blow through (intake charge venting out of the exhaust valves during the intake stroke), improves emissions, and improves power.
I'd guess that this is the best combination of motor parts ever stuck together by subaru for street use. I doubt the venerable 22B is any better.
Well, except that I like the old body style better, but at least the WRX isnt "surprised" anymore.
Joel
Tim, an answer to that question would be even more purely speculative. Variable cam timing allows you to run the necessary overlap at low end, off-boost, for good efficiency without hurting emissions, while still reducing overlap at the top end, where higher boost is likely, which reduces blow through (intake charge venting out of the exhaust valves during the intake stroke), improves emissions, and improves power.
I'd guess that this is the best combination of motor parts ever stuck together by subaru for street use. I doubt the venerable 22B is any better.
Well, except that I like the old body style better, but at least the WRX isnt "surprised" anymore.Joel
01-16-2003, 05:46 PM
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Here's that article from Garrett that highlights some interesting differences between the stock WRX turbo and the twin scroll turbo.
http://www.cmmstudio.com/G2001/g-innovate_tsth.html
Here's some more from Renault.
http://www.sae.org/automag/techbriefs_03-00/03.htm
So the twin-scroll turbo reduces engine combustion parasitics rather than improve the turbo's fan curve by reducing impeller inertia or doubling the number of impellers, etc.
Dave.
http://www.cmmstudio.com/G2001/g-innovate_tsth.html
Here's some more from Renault.
http://www.sae.org/automag/techbriefs_03-00/03.htm
So the twin-scroll turbo reduces engine combustion parasitics rather than improve the turbo's fan curve by reducing impeller inertia or doubling the number of impellers, etc.
Dave.
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