Are the STi 7 pistons hypereutetic or forged?
20 October 2003, 05:27 PM
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From MRT August newsletter:
2003/4 STi Engine
Last month we spoke about how the latest Sti Impreza does not have Forged Pistons, we want to clarify that this is for all (known) models other than the Australian model.
Here in oz the engine fitted to our local current STi is actually the same engine from last years model!
I presume this means the Type UK STi 7/MY02 pistons are forged, but the Type UK STi8/MY03 are hypereutetic.
rupert
2003/4 STi Engine
Last month we spoke about how the latest Sti Impreza does not have Forged Pistons, we want to clarify that this is for all (known) models other than the Australian model.
Here in oz the engine fitted to our local current STi is actually the same engine from last years model!
I presume this means the Type UK STi 7/MY02 pistons are forged, but the Type UK STi8/MY03 are hypereutetic.
rupert
20 October 2003, 06:03 PM
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John, for your information re: Sti7 & 8 Pistons & Rods
These engine do have steel connecting rods but they are the same as the regular wrx, the pistons are not like an aftermarket
forged one, they are an extruded piston. They look like a forged piston, there not as strong as one but are stronger than a cast piston and are lighter than a forged piston. They don't expand like a forged pistons when warmed up so smaller clearences are used to eliminate piston knock which aftermarket forged pistons have.
That explains the very tight piston to bore clearances....
Hope this helps?
Source Sam @ Rigoli Performance in Australia.
Regards
Conrad
These engine do have steel connecting rods but they are the same as the regular wrx, the pistons are not like an aftermarket
forged one, they are an extruded piston. They look like a forged piston, there not as strong as one but are stronger than a cast piston and are lighter than a forged piston. They don't expand like a forged pistons when warmed up so smaller clearences are used to eliminate piston knock which aftermarket forged pistons have.
That explains the very tight piston to bore clearances....
Hope this helps?
Source Sam @ Rigoli Performance in Australia.
Regards
Conrad
21 October 2003, 07:04 AM
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Interesting.......
as the official press release back in 2002 on the Subaru Australia website below clearly refers to forged pistons for the STi MY03.
Engine
Impreza WRX STi's amazing performance comes from a DOHC 2.0 litre turbocharged horizontally opposed quad-cam 16-valve Boxer engine.
It produces 195kW of power at 6,000rpm and 343Nm of torque at 4,000rpm. The Active Valve Control System electronically adjusts the intake valve timing through a range of 35 crankshaft degrees. This produces optimum power and torque while minimizing fuel consumption and emissions.
The high strength engine block features:
Semi closed deck design, providing reinforcement around cylinder tops, while maintaining the cooling advantage of a full open deck design.
Forged pistons, for heightened durability and strength under high thermal loads.
Connecting rod construction draws on new design and manufacturing processes introduced in Subaru’s highly successful H6-3.0 engine, used in the Outback H6.
Hollow inlet valves reduce valve train inertia, enabling the valves to follow the camshaft profile even at high engine speeds. Sodium-filled exhaust valves dissipate heat from the exhaust valve head.
An engine oil cooler is located between the oil filter and engine block.
A large diameter STi exhaust system completes the powerful engine package.
Turbocharger and intercooler
The IHI turbocharger features an A/R ratio of 15 which, in conjunction with the Active Valve Control System, provides the optimum in volumetric efficiency. (The A/R ratio of the turbocharger determines the characteristics of exhaust gas pressure production. 'A' represents the smallest area of the inlet of the turbine housing and 'R' represents the distance from the centre of the turbine shaft to the centre of the turbine-housing inlet).
A 15mm-taller bonnet scoop feeds air into the intercooler, which is 39per cent larger than standard Impreza WRX.
This reduces any restriction in the airflow. A driver-controlled water spray can be used to further lower intake air temperature under extreme conditions, for example when accelerating from low speed, when airflow through the intercooler is at a minimum.
ALSO www.rallispec.com list parts for sale below
ENGINES:
RST-0012 MY02 STi RA Spec C -- $9703
RST-0015 MY02 STi -- $9703
Revised cam profiles set the Spec C apart from the standard STi. Some examples of the Spec C have produced as much as 320hp on the dyno in completely stock form. Both engines use forged pistons, semi-closed deck block, and active valve control. The Spec C version is not group N legal so use the standard STi.
PISTONS:
RST-0108 MY03 EJ207 STi Piston Set -- $1022
This latest STi piston is a departure from previous years in that it is a cast aluminum design. However, we believe this to be a special hypereutectic material and STi claims a 120% increase in strength over their previous forged pistons. The high silicon content of the aluminum also has the benefit of providing exceptional scuff resistance and reduced thermal expansion which allows for the use of tighter clearances. Compression 8.0:1.
RST-0103 MY02 EJ207 STi Forged Piston Set -- $1022
RST-0102 Version 5/6 EJ207 STi Forged Piston Set -- $1022
RST-0101 Version 3/4 EJ20K STi Forged Piston Set -- $1022
Factory forged piston sets are capable of withstanding higher pressure and heat than a typical cast piston. This allows running higher boost pressure and/or closer to the knock limit without as much concern for piston damage. RST-0103 is a direct replacement in the US WRX. Compression 8.0:1.
I suppose the question remains open? STi MY02 = forged piston
STi MY03 = cast pistons
rupert
as the official press release back in 2002 on the Subaru Australia website below clearly refers to forged pistons for the STi MY03.
Engine
Impreza WRX STi's amazing performance comes from a DOHC 2.0 litre turbocharged horizontally opposed quad-cam 16-valve Boxer engine.
It produces 195kW of power at 6,000rpm and 343Nm of torque at 4,000rpm. The Active Valve Control System electronically adjusts the intake valve timing through a range of 35 crankshaft degrees. This produces optimum power and torque while minimizing fuel consumption and emissions.
The high strength engine block features:
Semi closed deck design, providing reinforcement around cylinder tops, while maintaining the cooling advantage of a full open deck design.
Forged pistons, for heightened durability and strength under high thermal loads.
Connecting rod construction draws on new design and manufacturing processes introduced in Subaru’s highly successful H6-3.0 engine, used in the Outback H6.
Hollow inlet valves reduce valve train inertia, enabling the valves to follow the camshaft profile even at high engine speeds. Sodium-filled exhaust valves dissipate heat from the exhaust valve head.
An engine oil cooler is located between the oil filter and engine block.
A large diameter STi exhaust system completes the powerful engine package.
Turbocharger and intercooler
The IHI turbocharger features an A/R ratio of 15 which, in conjunction with the Active Valve Control System, provides the optimum in volumetric efficiency. (The A/R ratio of the turbocharger determines the characteristics of exhaust gas pressure production. 'A' represents the smallest area of the inlet of the turbine housing and 'R' represents the distance from the centre of the turbine shaft to the centre of the turbine-housing inlet).
A 15mm-taller bonnet scoop feeds air into the intercooler, which is 39per cent larger than standard Impreza WRX.
This reduces any restriction in the airflow. A driver-controlled water spray can be used to further lower intake air temperature under extreme conditions, for example when accelerating from low speed, when airflow through the intercooler is at a minimum.
ALSO www.rallispec.com list parts for sale below
ENGINES:
RST-0012 MY02 STi RA Spec C -- $9703
RST-0015 MY02 STi -- $9703
Revised cam profiles set the Spec C apart from the standard STi. Some examples of the Spec C have produced as much as 320hp on the dyno in completely stock form. Both engines use forged pistons, semi-closed deck block, and active valve control. The Spec C version is not group N legal so use the standard STi.
PISTONS:
RST-0108 MY03 EJ207 STi Piston Set -- $1022
This latest STi piston is a departure from previous years in that it is a cast aluminum design. However, we believe this to be a special hypereutectic material and STi claims a 120% increase in strength over their previous forged pistons. The high silicon content of the aluminum also has the benefit of providing exceptional scuff resistance and reduced thermal expansion which allows for the use of tighter clearances. Compression 8.0:1.
RST-0103 MY02 EJ207 STi Forged Piston Set -- $1022
RST-0102 Version 5/6 EJ207 STi Forged Piston Set -- $1022
RST-0101 Version 3/4 EJ20K STi Forged Piston Set -- $1022
Factory forged piston sets are capable of withstanding higher pressure and heat than a typical cast piston. This allows running higher boost pressure and/or closer to the knock limit without as much concern for piston damage. RST-0103 is a direct replacement in the US WRX. Compression 8.0:1.
I suppose the question remains open? STi MY02 = forged piston
STi MY03 = cast pistons
rupert
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21 October 2003, 07:12 AM
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Interesting.....
Official press release back in 2002 on Subaru Australia website:
Engine
Impreza WRX STi's amazing performance comes from a DOHC 2.0 litre turbocharged horizontally opposed quad-cam 16-valve Boxer engine.
It produces 195kW of power at 6,000rpm and 343Nm of torque at 4,000rpm. The Active Valve Control System electronically adjusts the intake valve timing through a range of 35 crankshaft degrees. This produces optimum power and torque while minimizing fuel consumption and emissions.
The high strength engine block features:
Semi closed deck design, providing reinforcement around cylinder tops, while maintaining the cooling advantage of a full open deck design.
Forged pistons, for heightened durability and strength under high thermal loads.
Connecting rod construction draws on new design and manufacturing processes introduced in Subaru’s highly successful H6-3.0 engine, used in the Outback H6.
Hollow inlet valves reduce valve train inertia, enabling the valves to follow the camshaft profile even at high engine speeds. Sodium-filled exhaust valves dissipate heat from the exhaust valve head.
An engine oil cooler is located between the oil filter and engine block.
A large diameter STi exhaust system completes the powerful engine package.
ALSO www.rallispec.com lists
ENGINES FOR SALE:
RST-0012 MY02 STi RA Spec C -- $9703
RST-0015 MY02 STi -- $9703
Revised cam profiles set the Spec C apart from the standard STi. Some examples of the Spec C have produced as much as 320hp on the dyno in completely stock form. Both engines use forged pistons, semi-closed deck block, and active valve control. The Spec C version is not group N legal so use the standard STi.
PISTONS FOR SALE
STi Piston Set
RST-0108 MY03 EJ207 STi Piston Set -- $1022
This latest STi piston is a departure from previous years in that it is a cast aluminum design. However, we believe this to be a special hypereutectic material and STi claims a 120% increase in strength over their previous forged pistons. The high silicon content of the aluminum also has the benefit of providing exceptional scuff resistance and reduced thermal expansion which allows for the use of tighter clearances. Compression 8.0:1.
RST-0103 MY02 EJ207 STi Forged Piston Set -- $1022
RST-0102 Version 5/6 EJ207 STi Forged Piston Set -- $1022
RST-0101 Version 3/4 EJ20K STi Forged Piston Set -- $1022
Factory forged piston sets are capable of withstanding higher pressure and heat than a typical cast piston. This allows running higher boost pressure and/or closer to the knock limit without as much concern for piston damage. RST-0103 is a direct replacement in the US WRX. Compression 8.0:1
They also have pictures of the cast and forged pistons
rupert
Official press release back in 2002 on Subaru Australia website:
Engine
Impreza WRX STi's amazing performance comes from a DOHC 2.0 litre turbocharged horizontally opposed quad-cam 16-valve Boxer engine.
It produces 195kW of power at 6,000rpm and 343Nm of torque at 4,000rpm. The Active Valve Control System electronically adjusts the intake valve timing through a range of 35 crankshaft degrees. This produces optimum power and torque while minimizing fuel consumption and emissions.
The high strength engine block features:
Semi closed deck design, providing reinforcement around cylinder tops, while maintaining the cooling advantage of a full open deck design.
Forged pistons, for heightened durability and strength under high thermal loads.
Connecting rod construction draws on new design and manufacturing processes introduced in Subaru’s highly successful H6-3.0 engine, used in the Outback H6.
Hollow inlet valves reduce valve train inertia, enabling the valves to follow the camshaft profile even at high engine speeds. Sodium-filled exhaust valves dissipate heat from the exhaust valve head.
An engine oil cooler is located between the oil filter and engine block.
A large diameter STi exhaust system completes the powerful engine package.
ALSO www.rallispec.com lists
ENGINES FOR SALE:
RST-0012 MY02 STi RA Spec C -- $9703
RST-0015 MY02 STi -- $9703
Revised cam profiles set the Spec C apart from the standard STi. Some examples of the Spec C have produced as much as 320hp on the dyno in completely stock form. Both engines use forged pistons, semi-closed deck block, and active valve control. The Spec C version is not group N legal so use the standard STi.
PISTONS FOR SALE
STi Piston Set
RST-0108 MY03 EJ207 STi Piston Set -- $1022
This latest STi piston is a departure from previous years in that it is a cast aluminum design. However, we believe this to be a special hypereutectic material and STi claims a 120% increase in strength over their previous forged pistons. The high silicon content of the aluminum also has the benefit of providing exceptional scuff resistance and reduced thermal expansion which allows for the use of tighter clearances. Compression 8.0:1.
RST-0103 MY02 EJ207 STi Forged Piston Set -- $1022
RST-0102 Version 5/6 EJ207 STi Forged Piston Set -- $1022
RST-0101 Version 3/4 EJ20K STi Forged Piston Set -- $1022
Factory forged piston sets are capable of withstanding higher pressure and heat than a typical cast piston. This allows running higher boost pressure and/or closer to the knock limit without as much concern for piston damage. RST-0103 is a direct replacement in the US WRX. Compression 8.0:1
They also have pictures of the cast and forged pistons
rupert
