Subenet: Performance Parts FAQ

Struts

• What is the compression Rate? Front 2396 / 791 N, Rear 1668 / 690 N.
• What is the Rebound Rate? 0.3m/sec.
• What characteristics in under and over steering are affected by them? The vehicle characteristics remain neutral when the suspension kit is installed.
• What color are they? Red.
• Are they re-buildable? No, they are not re-buildable.
• Are they adjustable? No, they are not adjustable.
• Who is the manufacture? The manufacturer is Kayaba.
• What are the component sizes compared to stock? Strut piston diameter 39.92mm (STI version) vs. 22.00mm (Stock).
• What process is done on them that make them better than the others? The specifications for performance were derived from WRC Subaru Rally Car experience.
• Will they work on other models? No, they are designed specifically for the 02-03 WRX.

Springs

• What is the "Progressive Rate"? Front 38.0 N/m, Rear 33.4 N/m.
• What is the "Roll"? It will be less than the stock suspension system.
• What are the I/D's and O/D's? Inner diameter = 5.625", Outer diameter = 6.875"
• What is the "Free-Length"? Rear (300mm), Front (270mm).
• Will there be a height difference? Height remains the same.
• If so, what % will there be in height? Not applicable, see above.
• Will there be a stiffening difference? Yes, there is a difference.
• If so, what % will the stiffness be? The system is stiffer than stock.
• Who manufactures them for Subaru? The front springs are manufactured by Mitsubishi-Seiko and the rear springs are manufactured by Nippon-Hatsujo.
• What material are they made of? Steel.
• What process is done on them that make them better than the others? The specifications for performance were derived from WRC Subaru Rally Car experience.
• Will they work on other models? No, they are designed specifically for the 02-03 WRX.

Aluminum Arm Kit

• Are the bushings included? Yes, they are part of the kit.
• Do I need different bushings? No, they are part of the kit.
• Will they work on other models? No, they are designed specifically for the 02-03 WRX.

Stabilizer Kit

• Are they adjustable? No, they are non-adjustable.
• If adjustable, how many adjustments? See above.
• What material(s) are they made of? Steel.
• What process is done on them that make them better than the others? The specifications for performance were derived from WRC Subaru Rally Car experience.
• Does the bushing kit come with the Stabilizer kit? Yes.
• Can I reuse my original bushings? Yes, but it is not recommended.
• Will they work on other models? No, they are designed specifically for the 02-03 WRX

.Bushing Kit

• What material(s) are they made of? All the bushing materials remain the same although the material properties are modified with the exception of the rear cross-member rubber bushing which is changed to a steel insert.
• What process is done on them that make them better than the others? The specifications for performance were derived from WRC Subaru Rally Car experience.
• Does the bushing kit come with the Stabilizer kit? Yes.
• Can I use them on my original stabilizer? For sedan, the rear stabilizer remains the same and is not changed. For wagon, the front stabilizer remains the same and is not changed.
• Will they work on other models? No, they are designed specifically for the 02-03 WRX.

STI Short Throw Shifter

• What is the measurement difference that makes it short? Approximately a 30% reduction in the shift throw for WRX Impreza, Forester and Legacy models and 10% reduction in shift throw for WRX STi. Additionally for WRX STi, the amount of lateral play in the shifter is minimized.
• What material are they made of? The shifter is made of the same materials as the stock unit.
• What benefit will this have on my car? A quicker, crisper shift will be felt.
• Will they work on other models? P/N C1010FA001 has cross application to 1993-2006MY Subaru Impreza (excluding STi); 1998-2002MY Forester; 1995-2004 MY Legacy. All other part numbers have unique model application.

STI Muffler, WRX

• What are the inlet and outlet sizes? Inlet pipe dia. =60mm, Outlet pipe dia.= 101.25mm
• What are the sound decibel differences? Noticeable increase from stock.
• What material are they made of? Durable Stainless Steel (T304).
• Who manufactures them for Subaru? Sakamoto Industries (parent company of ELSA).
• What process is done on them that make them better than the others? The muffler is specifically designed to match the performance of the turbo WRX engine.
• Is there a horsepower increasing? Minimal. Horsepower cannot be noticeably increased because of the Performance Muffler alone.
• Is there a weight difference on these VS the stock? The Performance muffler weighs 2kg lighter than the OEM muffler.
• Is there a Chamber and/or Scavenging difference? The Performance muffler is made with the same back pressure as the OEM WRX to maintain the performance parameters.
• Will they work on other models? No, they are designed for 2002-2006 Impreza WRX applications only.

SPT Catback Exhaust, WRX and WRX STI

• What are the inlet and outlet sizes? Inlet pipe dia. =76mm, Outlet Pipe dia = 90mm
• What are the sound decibel differences? Noticeable increase from stock.
• What material are they made of? Durable Stainless Steel (T304).
• Who manufactures them for Subaru? Bosal - North America (made in South Africa).
• What process is done on them that make them better than the others? The muffler is specifically designed to match the performance of the turbo WRX and WRX STI engines.
• Is there a horsepower increasing? Minimal. Horsepower cannot be noticeably increased because of the Performance Muffler alone.
• Is there a weight difference on these VS the stock? 1kg lighter.
• Is there a Chamber and/or Scavenging difference? The Performance muffler is made with the same back pressure as the OEM WRX to maintain the performance parameters.
• Will they work on other models? No, they are designed for Impreza WRX and WRX STI applications only.

17” FHI 5-Spoke Wheels

• What material are they made of? Aluminum alloy.
• What manufacturing process is used to produce them? They are pressure cast for more strength than cast wheels.
• What is their weight? 8.35 kg (18.4 lbs.).
• What is their offset? 55 mm.
• Why does Subaru use “this offset”? Since Subaru uses the horizontally opposed engine for its inherent low center of gravity the engine is wider and pushes the drive train components further away from the vehicle centerline therefore a large offset in the wheels is required for optimum performance.
• Will they work on other models? No, the wheel/tire combination is designed specifically for the WRX.
• What is the recommended tire? Bridgestone Potenza RE011 size 215/45R-17.

17" BBS Multi-Spoke Wheels

• What material are they made of? Aluminum Alloy.
• What process is done on them that make them better than the others? The wheel are specifically designed by BBS for Subaru.
• Are they Forged? Yes, they are forged.
• What in their weight. 6.8 kg (15 lbs.).
• What is their offset? 55 mm.
• Why does Subaru use "this" offset? Since Subaru uses the horizontally opposed engine for its inherent low center of gravity the engine is wider and pushes the drive train components further away from the vehicle centerline therefore a large offset in the wheels is required for optimum performance.
• Will they work on other models? No, the wheel/tire combination is designed specifically for the WRX.
• What is the recommended tire? Bridgestone Potenza RE011 size 215/45R-17.

Performance Strut Set, 1998-2001 Impreza 2.5RS

• What is the compression Rate? Variable setting #1 like OE Setting.
• What is the Rebound Rate? Variable setting #1 like OE Setting.
• What characteristics in under and over steering are affected by them? The vehicle characteristics remain neutral when the suspension kit is installed.
• What color are they? Red.
• Are they re-buildable? No, they are not re-buildable.
• Are they adjustable? Yes, the damping force is adjustable.
• Who is the manufacture? The manufacturer is KYB.
• What are the component sizes compared to stock? The units are dimensionally identical to OEM.
• What process is done on them that make them better than the others? When driving on smooth surfaces, strut movements are relatively slow and the AGX valving allows the strut to travel freely. As road conditions get rougher, the strut is compressed faster. The AGX (3 stage valve action) strut responds instantly to make response firmer, maintaining tire contact and vehicle control.

Performance Spring Set, 1998-2001 Impreza 2.5RS

• What is the "Progressive Rate"? Front 30.0 N/m, Rear 33.0 N/m.
• What is the "Roll"? It will be less than the stock suspension system.
• What are the I/D's and O/D's? (Front) Inner diameter = 5.610", Outer diameter = 6.710" & (Rear) Inner diameter = 5.433", Outer diameter = 6.440"
• What is the "Free-Length"? Rear (330mm), Front (270mm).
• Will there be a height difference? Lower by 1.0" (Front), Lower by 1.2" (Rear).
• Will there be a stiffening difference? Yes, there is a difference.
• If so, what % will the stiffness be? The system is stiffer than stock.
• Who manufactures them for Subaru? Eibach.
• What material are they made of? Steel.
• What process is done on them that make them better than the others? There are a number of different things that separates Eibach from other performance spring manufacturers, but it can be summed up in a single word, “quality”. Raw material is the most important aspect in the manufacturing of a high performance spring. This is why Eibach Springs sources the finest material from around the globe, utilizing only a handful of wire mills that are able to meet our stringent quality demands. To produce our springs, Eibach’s highly skilled production team utilizes world-renowned Wafios machines, the most accurate CNC coilers in the industry. Finally, Eibach Springs has made a substantial investment in state-of-the-art testing equipment, enabling our quality assurance department to continually test our performance springs for optimum precision and quality. The result is the finest springs in the industry.
• Will they work on other models? No, they are designed specifically for the 1998-2001 Impreza RS Sedan.

Performance Spring Set, 02-03 WRX Sedan

• What is the "Progressive Rate"? Front: 33.80 N/mm, Rear: 28.20 N/mm.
• What is the "Roll"? It will be less than the stock suspension system.
• What are the I/D's and O/D's? (Front) Inner diameter = 144.50 mm, Outer diameter = 171.50 mm & (Rear) Inner diameter = 130mm, Outer diameter = 154.50 mm
• What is the "Free-Length"? Front: 253 mm, Rear: 308 mm.
• Will there be a height difference? Lower by approximately 1.4" (Front), Lower by 1.2" (Rear).
• Will there be a stiffening difference? Yes, there is a difference.
• If so, what % will the stiffness be? The system is stiffer than stock.
• Who manufactures them for Subaru? Eibach.
• What material are they made of? Steel.
• What process is done on them that make them better than the others? There are a number of different things that separates Eibach from other performance spring manufacturers, but it can be summed up in a single word, “quality”. Raw material is the most important aspect in the manufacturing of a high performance spring. This is why Eibach Springs sources the finest material from around the globe, utilizing only a handful of wire mills that are able to meet our stringent quality demands. To produce our springs, Eibach’s highly skilled production team utilizes world-renowned Wafios machines, the most accurate CNC coilers in the industry. Finally, Eibach Springs has made a substantial investment in state-of-the-art testing equipment, enabling our quality assurance department to continually test our performance springs for optimum precision and quality. The result is the finest springs in the industry.
• Will they work on other models? No, they are designed specifically for the 2002-2003 Impreza WRX Sedan.

Strut Tower Brace, 1998- 2001 Impreza

This product is not available for the 2002MY and up Impreza.
• Are they adjustable? No, they are non-adjustable.
• What material(s) are they made of? The painted red version is steel. The black carbon fiber STI version the tubes are made of carbon fiber and the fittings and brackets are aluminum alloy. This component is manufactured by Fuji Heavy Industries Aerospace Division.
• What is the weight difference between steel and carbon fiber? The steel weighs 2.72 lbs. and the carbon fiber including mounting brackets weighs 3.48 lbs.
• What process is done on them that make them better than the others? They are tested to meet stringent requirements developed by FHI.
• Will they work on other models? No, they are designed for 98-01 Impreza applications only.

STI Adjustable Strut/Spring Kit, all Impreza Sedan 04+ except 05+ STi

Struts:
• What is the compression Rate?
1st: Front 770N , Rear 570N at 0.3m/sec.
2nd: Front 840N , Rear 620N at 0.3m/sec.
3rd: Front 880N , Rear 650N at 0.3m/sec.
4th: Front 960N , Rear 680N at 0.3m/sec.
• What is the Rebound Rate?
1st: Front 1370N , Rear 1060N at 0.3m/sec.
2nd: Front 1580N , Rear 1150N at 0.3m/sec.
3rd: Front 1690N , Rear 1240N at 0.3m/sec.
4th: Front 1890N , Rear 1350N at 0.3m/sec.
• What characteristics in under and over steering are affected by them? Adjustable.
• What color are they? STI Cherry red.
• Are they re-buildable? No, they are not re-buildable.
• Are they adjustable? 4-position adjustable damping force and height.
• Who is the manufacturer? STI.
• What are the component sizes compared to stock? Strut cylinder diameter 39mm (STI parts = STI ver.) vs. 22mm (WRX & RS).
• What process is done on them that make them better than the others? The specifications for performance were derived from WRC Subaru Rally Car experience.
• Will they work on other models? They are designed for 04+ WRX & RS SEDAN and 04 STi.

Springs:
• What is the “Progressive Rate”? Front 60N/mm, Rear 50N/mm.
• What is the “Roll”? It changes with conditions.
• What are the I/D’s and O/D’s? Inner diameter = 65mm, Outer diameter = 88mm (front), 86mm (rear).
• What is the “Free-Length”? Front (227mm), Rear (203mm).
• Will there be a height difference? Adjustable.
• If so, what % will there be in height? Adjustable.
Will there be a stiffening difference? Yes, 50% stiffer for 04 STi, 100% stiffer for WRX, and 130% stiffer for 2.5RS / 2.5i.
• Who manufacturers them for Subaru? STI.
• What material are they made of? Steel.
• What process is done on them that make them better than the others? The specifications for performance were derived from WRC Subaru Rally Car experience.
• Will they work on other models? They are designed for 04-05 WRX & RS SEDAN and 04 STi.

STI Strut / Spring Kit, all Impreza Sedan 04+ except 05+ STi

Struts:
• What is the compression Rate? Front 840N, Rear 620N at 0.3m/sec.
• What is the Rebound Rate? Front 1580N, Rear 1150N at 0.3m/sec.
• What characteristics in under and over steering are affected by them? The vehicle characteristics remain neutral when the suspension kit is installed.
• What color are they? STI Cherry-red.
• Are they re-buildable? No, they are not re-buildable.
• Are they adjustable? No, they are not adjustable.
• Who is the manufacturer? STI.
• What are the component sizes compared to stock? Strut cylinder diameter 39mm (STI parts-STI ver.) vs. 22mm (WRX & RS).
• What process is done on them that make them better than the others? The specifications for performance were derived from WRC Subaru Rally Car experience.
• Will they work on other models? They are designed for 04+ WRX SEDAN. They can also be used for 04+ 2.5RS / 2.5i SEDAN & 04 STi.

Springs:
• What is the “Progressive Rate”? Front 60N/mm, Rear 50N/mm.
• What is the “Roll”? It changes with conditions.
• What are the I/D’s and O/D’s?
Front Inner Diameter = 124 to 143mm , Outer Diameter = 153 to 172mm.
Rear Inner Diameter = 100 to 130mm , Outer Diameter = 127 to 157mm.
• What is the “Free-Length”? Front (234mm), Rear (290mm).
• Will there be a height difference? Yes:
STi: approximately 15mm lower
WRX / 2.5RS / 2.5i: approximately 22mm lower
• Will there be a stiffening difference? Yes:
STi: 50%
WRX: 100%
2.5RS / 2.5i: 130%
• Who manufactures them for Subaru? STI.
• What material are they made of? Steel.
• What process is done on them that make them better than the others? The specifications for performance were derived from WRC Subaru Rally Car experience.
• Will they work on other models? They are designed for 04+ WRX SEDAN. They can also be used for 04+ 2.5RS / 2.5i SEDAN & 04 STi.

STI Spring Set, Impreza Sedan 04+ except STi

• What is the “Progressive Rate”? Front 39N/mm , Rear 34N/mm.
• What is the “Roll”? It changes with conditions.
• What are the I/D’s and O/D’s?
Front Inner diameter = 124 to 143mm , Outer diameter = 152 to 171mm
Rear Inner diameter = 100 to 130mm , Outer diameter = 126 to 156mm
• What is the “Free-Length”? Front (270mm), Rear (308mm)
• Will there be a height difference? Approximately 15mm lower.
• Will there be a stiffening difference? Yes, 40% stiffer for WRX and 45% for 2.5RS / 2.5i.
• Who manufacturers them for Subaru? STI.
• What material are they made of? Steel.
• What process is done on them that make them better than the others? The specifications for quality were derived from experience of FHI.
• Will they work on other models? They are designed for 04+ WRX SEDAN. They can also be used for 04+ 2.5RS or 2.5i SEDAN.

STI Spring Set, Impreza Wagon, 04+

• What is the “Progressive Rate”/? Front 39N/mm , Rear 34N/mm
• What is the “Roll”? It changes with conditions.
• What are the I/D’s and O/D’s?
Front Inner diameter = 124 to 143mm , Outer diameter = 152 to 171mm
Rear Inner diameter = 100 to 130mm , Outer diameter = 126 to 156mm
• What is the “Free-Length”? Front (270mm), Rear (308mm
• Will there be a height difference? Yes, approximately 15mm lower.
Will there be a stiffening difference? Yes: 40% stiffer for WRX and 45% stiffer for 2.5RS / 2.5TS/ 2.5i.
• Who manufacturers them for Subaru? STI.
• What material are they made of? Steel
• What process is done on them that make them better than the others? The specifications for quality were derived from experience of FHI.
• Will they work on other models? They are designed for 04+ WRX WAGON. They can also be used for 04+ 2.5TS / 2.5RS / 2.5i WAGON.

STI Sway Bar Kit, Front, WRX Sedan 04+

• Are they adjustable? No, they are non-adjustable.
• What material(s) are they made of? Steel.
• What process is done on them that make them better than the others? The specifications for quality were derived from the experience of FHI.
• Does the bushing kit come with the Stabilizer kit? Yes.
• Can I reuse my original bushings? No, the diameter is larger than the stock. So, the bushing must be replaced.
• Will they work on other models? No, they are designed specifically for 04+ WRX SEDAN.

STI Sway Bar Kit Rear, 2004+ Impreza except STi

• Are they adjustable? No, they are non-adjustable.
• What material(s) are they made of? Steel.
• What process is done on them that make them better than the others? The specifications for quality were derived from experience of FHI.
• Does the bushing kit come with the Stabilizer Kit? Yes.
• Can I reuse my original bushings? No, the diameter is fatter than the stock. So, the bushing must be replaced.
• Will they work on other models? They are designed for 04+ WRX SEDAN & WAGON. They can also be used for 04+ 2.5RS / 2.5TS / 2.5i SEDAN & WAGON.
STI Performance Timing Belt, Impreza WRX
• What is the recommended replacement interval for the timing belt? The recommended replacement interval is 62,500 miles (100,000 km).
STI Adjustable Strut/Spring Kit, Impreza STi 05+
Struts
• What is the compression rate?
Position
Front
Rear
1
850
650
2
880
700
3
900
720
4
1000
750
Measured in Newtons, at 0.3 m/sec
• What is the rebound rate?
Position
Front
Rear
1
1550
1150
2
1650
1200
3
1700
1250
4
1800
1300
Measured in Newtons, at 0.3 m/sec
• Is understeer or oversteer affected? Adjustable.
• What color are they? STI Cherry Red.
• Are they rebuildable? No.
• Are they adjustable? 4 position adjustable damping force.
• Who is the manufacturer? STI
• What is the strut cylinder diameter? 35mm.
• What makes these better than other setups? The performance specifications were derived from Subaru WRC experience.
• Will they work on other models? No, they only fit the unique strut mounts of the Impreza STi, 2005+.

Springs
• What is the progressive rate? Front 60N/mm, rear 50N/mm.
• What is the roll? Changes with conditions.
• What are the inner and outer diameters? ID=124-143mm front, 100-130mm rear. OD=153-172mm front, 127-157mm rear.
• How much is the vehicle lowered by? About 15mm, or 1%.
• How much stiffer than stock? 35% front, 30% rear.
• Who manufactures them for Subaru? STI.
• What material are they made of? Steel.
• What makes these better than other setups? The performance specifications were derived from Subaru WRC experience.
• Will they work on other models? No.