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Subaru WRX and STi Exhaust general info

Subaru WRX and STi Exhaust general info:

The primary purpose of an aftermarket exhaust is to remove or replace the stock catalytic converter(s) with a better flowing unit. It also increases the exhaust diameter for better flow. The term “aftermarket exhaust” can be broken down into the three main types:

1. Turbo back exhaust (TBE) covers items 1-4 as described below.
2. Cat back exhaust (CBE) covers items 3&4 as described below.
3. Axle back exhaust (ABE) covers item 4 as described below.

The stock WRX Subaru exhaust consists of:

1. Downpipe (with cat) | 2. Midpipe (with cat) | 3. Rear Exhaust Pipe | 4. Axle Back Muffler

The stock WRX Subaru exhaust consists of: 1. Downpipe (with cat) | 2. Midpipe (with cat) | 3. Rear Exhaust Pipe | 4. Axle Back Muffler
The stock WRX Subaru exhaust consists of: 1. Downpipe (with cat) | 2. Midpipe (with cat) | 3. Rear Exhaust Pipe | 4. Axle Back Muffler

Keep in mind that the above information is catered to the 2002-2005 WRX and is likewise applicable to all years of the STi, though there are slight variations. For example, the STi (all years) has a catless uppipe and the 2006+ WRX has a one piece downpipe/midpipe.

HP gain is dependent on the type of exhaust chosen. TBE gains are 20-30HP. CBE gains are 5-15HP. ABE gains are 5-10HP. These figures are highly debated as different manufacturers use different dynos with different cars with different levels of mods. It also varies because exhausts use different amounts of catalytic converters or are catless.

What about overall fitment between the WRX and STi or different model years? All OEM or aftermarket exhausts designed for 02-07 WRX/STi will fit either the 02+ WRX sedan/wagon or 04+ STi. Occasionally, you will have a slight fitment issue with some models (moreso if your car has the optional rear differential cover) that usually get be fixed via hanger adjustment, longer exhaust hangers etc. 06+ models have fitment issues with some exhausts (mainly the muffler portion) due to the new rear diffuser.

I have an 06+ WRX, is the downpipe the same? No. The 2006+ WRX has a unique exhaust in that it’s downpipe is both the downpipe and midpipe sections of the “older” exhaust. This means you must use a “long” downpipe to bolt up to the rest of your exhaust system. A full TBE will fit fine, but when replacing just the downpipe, you must use a long downpipe. Check with your Vendor for other possible fitment issues prior to ordering.

STi intercooler install on a Subaru WRX

You can easily install the upgraded STI top-mount intercooler in your garage using basic tools.

1. Disconnect your battery and make sure you have all the necessary tools. You need a flat bladed screwdriver, a 10mm wrench, and a 12mm wrench. Consider the picture before you in the engine compartment. The parts you’re looking for are centered on top of the engine. You need the new intercooler, an STI Y-pipe and inlet elbow and a new gasket for the bypass or blow-off valve. You also need the STi air conditioning line bracket for the firewall.

This is the stock WRX engine with the stock intercooler on top.
This is the stock WRX engine with the stock intercooler on top.

2. Two 12mm bolts that hold the intercooler to its mounting bracket on either side of the cooler. On the passenger side, note that there’s an open hole in the bracket—this hole is there to accommodate the STI intercooler. Three 10mm bolts hold a metal tube to the front of the intercooler, and two 12mm bolts that attach the bypass valve. Underneath the intercooler on the passenger side, there’s a hose clamp that holds the Y-pipe to the turbo, and there’s another hose clamp in front that holds the intercooler to the throttle body.

Note the extra bolt-hole Subaru thoughtfully placed in just the right spot for an STI intercooler.
Note the extra bolt-hole Subaru thoughtfully placed in just the right spot for an STI intercooler.
You need to undo all these bolts along the front of the intercooler.
You need to undo all these bolts along the front of the intercooler.

3. Loosen the hose clamps first (and hopefully the one under the intercooler is oriented to make this easy) and then undo all the bolts. The intercooler should lift out and take the Y-pipe with it. Leave the bypass valve on the intake manifold—you don’t need to totally disconnect it. You might need to wiggle it loose, but don’t pull too hard.

Carefully lift out the intercooler and the hoses should come free if you’ve loosened the clamps.
Carefully lift out the intercooler and the hoses should come free if you’ve loosened the clamps.

VF39 STi turbocharger onto your WRX/Forester

VF39 STi turbocharger onto your WRX/Forester:

Swapping a STi VF39 turbocharger onto your WRX/XT is really easy. Find out here the step by step process on swapping a VF39 onto your Subaru WRX/XT.

You can buy a brand new VF39 Turbocharger here:

Subaru 14411aa5729L Turbocharger

A lot of people seem to be getting hung up on the oil return lines and coolant lines. The coolant lines and banjo bolts from the TD04 ARE interchangeable if your vf39 doesn’t have them (mine didn’t). The oil return line is not and must be modified in order to fit the vf39, (mine had it). Or get a new one from the dealer. I will explain in the pictures when I get to these items.

First remove the intercooler, pretty self explanatory there are 2 bolts that it mounts to, 2 on the BPV and the hoses. Done Deal. Next the heat shield. You should be somewhere around here:

VF39 STi turbocharger onto your WRX/Forester: Start removing the head shield and downpipe.
VF39 STi turbocharger onto your WRX/Forester: Start removing the head shield and downpipe.

 

Remove the downpipe:

VF39 STi turbocharger onto your WRX/Forester: Start removing the downpipe.
VF39 STi turbocharger onto your WRX/Forester: Start removing the downpipe.

Then remove the bolt for the oil inlet (top of the turbo), and start removing the coolant lines (2 lines coming off the side of the turbo 1 goes up 1 goes down). Be careful as you will lose coolant during this step be prepared to either catch it under the car or plug the line:

VF39 STi turbocharger onto your WRX/Forester: Remove coolant lines and oil lines.
VF39 STi turbocharger onto your WRX/Forester: Remove coolant lines and oil lines.

Then remove the 3 bolts that hold the turbo to the uppipe. Loosen from the intake remove vacuum lines and anything else attached to the turbo and you should be ready to take it off. The hose that the oil return line fits into is directly under the turbo and you should probably just lift straight out. Try to leave the hose where it is and lift the line out.

Now that the turbo is off you can start swapping out the parts you need from the td04. The coolant lines from the TD04 will fit the VF39 however they are attached and too close together to fit directly on the VF39 see pic:

VF39 STi turbocharger onto your WRX/Forester: changing out oil lines.
VF39 STi turbocharger onto your WRX/Forester: changing out oil lines.

2004 – 2007 USDM STi breakdown

2004 – 2007 USDM STi breakdown:

A Stock 2005 USDM STi
A Stock 2005 USDM STi

Rev. D (2004)

In 2004, Subaru of America announced it would sell the WRX STi. Subaru Tecnica International’s president said in an interview with Road & Track magazine that he wished to beat the Mitsubishi Lancer Evolution in the US. Thus, each iteration of the US-spec WRX STi is essentially the same as the respective J-spec STi Spec C. All part numbers matched up, including the part-numbers for the glass windows and dampeners.

However, instead of the EJ207, the USA receives the first EJ257, a 2.5 liter version of the EJ207. Unlike the EJ207, it features hypereutectic cast pistons as opposed to the forged pistons in the EJ207. The steering rack is the standard STi’s 15.2:1 instead of the Spec C’s 13:1

2004 – 2007 USDM STi breakdown:

Rev. E (2005)
As with the Japanese-spec C models, US-spec STis received additional rear fender flaring in order to allow an increase in wheel size. The wheel size went from 17″ x 7.5″ to 17″ x 8″. In accordance with the increased wheel width, steering lock-to-lock turns have been reduced. Wheel hub strength was improved. The P.C.D. was changed from 5 x 100 to 5 x 114.3. The Suretrac front LSD in the 04 model was replaced with a helical unit, the rear differential remains the same clutch type unit. Torque split is set at 35/65. In the interior, the Stereo became standard. The badging has been revised and different look was given to the steering wheel, shift knob, HVAC controls, and center console.

2004 – 2007 USDM STi breakdown:

Rev. F (2006)
The US-spec STIs receive the same face lift as the Japanese-spec STIs. Mechanically speaking, the DCCD (Driver Controlled Center Differential) and the engine mounts have been changed. Like the Japanese-spec STIs engine mounts were changed from metal to liquid-filled plastic mounts to reduce vibrations into the car’s cabin. On the largest Impreza forum, North American Subaru Impreza Owners Club (NASIOC), 2006 owners have had issues with these plastic engine mounts.

The manufacturer will replace them, under warranty, if broken, with the 2005 rubber and metal mounts. Later 2006 vehicles were equipped from the factory with 2005 mounts. The center differential is updated with the addition of a mechanical limited slip mechanism to supplement the electromagnetic DCCD. The torque split is changed to 41/59. The 2006 STI weighs approximately 3,350 lb (1,520 kg).

THE THIRD GENERATION SUBARU IMPREZA WRX STI

Impreza WRX STi
Third generation STi

Third generation (2008-present)
Third generation (GR)
Production 2008-present
Body style(s) 5-door hatchback
4-door sedan(2011-)
Engine(s) 2.0L 304 hp (227 kW) H4
2.5L 305 hp (227 kW) H4
Transmission(s) 6-speed manual
5-speed automatic (w/SPORTSHIFT manual mode) (Japan, Hong Kong, Singapore, Indonesia, and Australia only)
Wheelbase 103.3 in (2,624 mm)
Length 173.8 in (4,415 mm)
Width 70.7 in (1,796 mm)
Height 58.1 in (1,476 mm)
Curb weight 3,373 lb (1,530 kg)
Related Subaru Forester
Subaru Impreza
Subaru Impreza WRX

Subaru Impreza WRX STI 2008The 2008 STI has received a higher degree of parts to differentiate it from its Impreza WRX brethren. Unlike the Impreza WRX, the STI uses aluminum suspension components, is only available as a 5-door hatchback, and has different fenders that are 2.2 in (56 mm) wider. It adopted “Subaru Intelligent Chassis Design” and “Dynamic Chassis Control Concept”. The turbo forces air through a larger top-mount-intercooler which has lost the red “STI” that was on previous generations. It is the first generation of this model with an automatic transmission which is able to import to outside Japan.

Like other 2008 Impreza models, the 2008 STI benefits from a lower polar moment of inertia due to smaller overhangs, and also features a double wishbone rear suspension.[16] The car also borrows new intake and exhaust components from the Legacy GT platform.

The latest Impreza WRX STI features Multi-mode Vehicle Dynamics Control (VDC) with “Normal”, “Traction”, and “Off” modes, Subaru Intelligent-Drive (SI-Drive) with 3 modes: Intelligent, Sport, and Sport Sharp (S#), and Multi-mode Driver’s Controlled Centre Differential (DCCD). The DCCD enables driver to select the manual or auto: “auto”, “auto+”, and “auto-” mode in order to distribute the torque based on driving preference or conditions.

Subaru Impreza WRX STI (Japan)The JDM version has a 2.0L 308 PS (227 kW; 304 bhp) EJ207 engine with a Twin scroll turbocharger, while other versions of the car have a 2.5L 300 PS (221 kW; 296 bhp) EJ257 engine with a single-scroll VF48 turbocharger.

5spd Subaru WRX five speed manual tips and tricks

5spd Subaru WRX five speed manual tips and tricks:

So you’ve got this noise coming from your 5spd transmission. It is starting to whine when you’re on/off the throttle. The sound seems to come right from below like around the shifter area. You may be a victim of the infamous falling apart center differential!

Don’t be too worried, transmissions are a dime a dozen! You still have the option to go 6spd or another 5spd transmission with different gear ratios if you choose.

 5spd: The damage. Most times the rear cover will back out minor like this photo. Other times it will completely come off. You can see the circlip survived this incident.
5Spd: The damage. Most times the rear cover will back out minor like this photo. Other times it will completely come off. You can see the circlip survived this incident on this WRX

Don’t wet sand a carbon fiber hood.

This guy had a bright idea of trying to sand his carbon fiber hood on his Subaru. Body work should sometimes be left to a professional.  Especially if you want to wet sand carbon fiber. It’s extremely dangerous if you don’t wear the proper PPE. All of the small particles can cause extensive damage to your lungs.

Sandingcarbonfiber

 

With these cheaper carbon fiber hoods once the clear coat is this damaged and down to the carbon fiber it’s safer for your health to have a professional look it to determine if it’s salvageable or not.[amazon template=image&asin=Subaru][amazon template=image&asin=subaruidiots-20]