FAQ: Subaru Legacy 2.5i

thanks shtbxr22, I will do that and see is the motor is bad thanks.

I would like to add to the list, 05's have TOPFEED injectors not sidefeeds. Learned that one the hard way.

looking to build customs tips with UEL can some explain more about the exhaust system... like what pipes are between the axle back and the headers. tell me if i have it right.

 

mufflers-ypipe-mid pipe-headers

 

is that right?

your forgetting the cat, inbetween midpipe and headers.

 

Check this na section, its been heavily documented the solutions for 06+ 2.5is who want uel headers.

Yeah, look for my posts in gee-otto's thread about the modded manifold for 2.5i

So I finally had a chance to install uel headers, CDN I read that you went through many o2 sensors while you had them on, did you manage to find a solution to it?

 

I see rallitek has a rear o2 sensor spacer, but I thought I read your front o2 sensors were going?

 

Other than the steering line (which I'm going to bend a bit more for clearance or put some wrap inbetween) , is there anything else I should keep an eye out over time?

 

They sound so nice though~ Definitely made me fall in love with the car again.

It was the fronts that have been going... basically once a year. I did the last one myself - had a couple covered under warranty but no more. Really not that hard to do so I'll do it again should another fail.

 

Until the last one went, I thought I had the issue licked after having wrapped the headers. I definitely recommend wrapping or coating the headers to retain a bit more heat in the pipe, which should help the front O2. If you can find a good deal on coating them, go that route as I think it has more longevity. I lost my skidplate this winter so now my header wrap is exposed under the car and I don't think it will last all that long. I plan to get my headers ceramic coated next time round.

 

The steering line can actually be moved up a bit - loosen the clamps and there's a bit of movement. I also had my headers tweaked a bit at a muffler shop so that part sat slightly lower as well.

How can we make.exhaust louder

If you have the money and want something that's high-quality and bolt-on, get some AVO mufflers. You can buy them from AVO directly, username apexjapan, or from Fred Beans Parts.

 

The cheaper alternative is to buy a pair of universal mufflers, e.g. Magnaflow, and bring them to your local exhaust shop so they can chop off your OEM mufflers and weld-on the aftermarket mufflers.

Thanks, I've been looking all over for something like this...

 

This FAQ is a summary of commonly asked questions and comments that I’ve come across. Thought I would throw this together as there seems to have been an increase of 2.5i owners on the forum as of late (welcome).

 

2005-2009 BP/BL Subaru Legacy 2.5i

 

1) Engine- How can I get more power out of my car?

Well, this is not an easy task, there really are only a very limited number of modifications available to increase power in the N/A 2.5 engine. This is a list of “bolt-on” modifications that can net you minimal gains:

 

-- high flow intake panel air filter:

increase flow of air towards engine. many types available from several manufacturers. AVO filter is used with high success from many members due to its ease of maintenance (no oil required) and easy cleaning (soap + water)

 

-- throttle body spacer:

supposedly will allow for increased efficiency in combustion by tumbling the incoming air charge. Available from Group-A

 

-- lightweight crank pulley as well as alternator/steering pulleys

decrease in rotational mass of the engine will allow it to spin more freely. Available from several manufacturers, Perrin, Group-A, Cobb etc

 

-- intake manifold spacers (potentially has greatest benefit):

if you examine the engine assembly you will note that the intake manifold sits on top of the engine block and as such becomes very hot over the course of engine operation, manifold spacers separate the intake manifold and decrease the temperature of the incoming air. Available from Grimspeed

 

http://www.grimmspeed.com/images/product_images/phenolic_spacer_coldhot_diagram_2.jpg

 

http://www.grimmspeed.com/images/product_images/phenolic_spacer_coldhot_diagram_3.jpg

(diagrams taken from Grimmspeed website illustrating the concept for STi engines which feature a metal intake manifold as well along with TMIC)

 

2) Intakes- Can I put CAI on my car to increase HP?????

Many inquire about the use of a CAI (cold air intake) for gains but particularly with intakes that replace the stock air box (cone type filters) it can throw off the MAF sensor and cause the engine to run too lean, or rich to compensate. Some have also run into issues with CELs. There is a more detailed article here from NASIOC:

 

http://forums.nasioc.com/forums/showthread.php?t=1471819

 

Generally it’s not recommended and is more reliable to use a high flow filter (see above) with the stock air box. However, there are also members who have had success with CAIs, so not to say it’s impossible. Usually intakes for the Impreza 2.5RS will fit as they have essentially the same basic engine design.

 

Recent developments (06-2010) by AVO japan on a 2.5i platform have shown that their GT power filter kit is compatible with the 2.5i, full results still pending

 

3) Exhaust

“Where can I get the boxer rumble that Subaru is so famous for?” the rumble that is infamous on WRX and STi’s (also the LGT) is due to the unequal exhaust length (UEL) headers. Unfortunately the 2.5i features equal length headers and thus does not emit the noted boxer rumble.

 

However, there are several aftermarket exhaust options available, though they will not give your car the boxer rumble sound, they can still change the exhaust note favorably. All axleback options for the LGT will bolt right up to the 2.5i. The SPTv2 CBE has also been successfully installed on a 2.5i as well. This link http://legacygt.com/forums/showthread.php/exhaust-audio-video-clip-compilation-thread-2-5i-edition-130408.html contains a compilation of aftermarket exhausts for the 2.5i

 

Aftermarket UEL headers can be fit onto the 2.5i, but at the moment there are no plug and play solutions available. See this thread for more details on how to customize the header setup for the 2.5i http://legacygt.com/forums/showthread.php/subie-boxer-rumblei-153134.html

 

4) Suspension Modifications

All of the Legacy GT suspension components are interchangeable with the 2.5i, as such, all aftermarket components for the LGT will also work in favor for the 2.5i

 

The only suspension piece that is not compatible is the front sway bar, however Rallitek has been kind enough to fabricate a 2.5i specific front sway bar. It is advisable to use reinforced mounts and brackets when installing sway bars as this has been a noted weak point in our suspension (both the LGT and 2.5i). In addition to the Rallitek front sway, it has been found that the 25mm front sway from the Subaru Tribeca is compatible with the 2.5i, more on that here:

 

http://www.legacygt.com/forums/showthread.php?t=111718

 

edit: aftermarket front lower arm bars/underbracing are also not compatible, this is due to different configuration of the exhaust piping and heatshield which prevent the FSB and bracing from fitting correctly.

 

With regards to the OEM struts, it is generally believed the 2.5i has the same struts with slightly softer valving, but this is unconfirmed. The external housing and suspension assembly is the same however, thus all Legacy GT parts, OEM and aftermarket will bolt right up, including:

 

-- coilovers

-- aftermarket struts (Bilstein, Konis, Tokico, Ohlins etc)

-- aftermarket springs

-- rear sway bar

-- strut tower bars

-- rear sub-frame braces

-- misc components (LCAs, LCA/steering bushings etc)

-- etc (they all fit)

 

This is probably the single greatest area that 2.5i owners can take advantage of with regards to aftermarket modifications and is likely the most worthwhile investment for your aftermarket dollars. Coupled with a set of top rubber, the 2.5i can be an excellent machine through twisties or auto-x.

 

5) Brakes

LGT and the 2.5i do not share the same brake platform and thus aftermarket LGT brake components *are not* direct fitment to the 2.5i's brake system (pads/rotors/calipers are diff sizes). However, a full LGT brake swap is possible and theoretically the aftermarket BBK options (Brembo etc) for the LGT should also fit on the 2.5i but likely not necessary as the LGT brake system should suffice (particularly with aftermarket pads and rotors)

 

If a full swap is not something you'd want to tackle, there are some aftermarket brake pads options from Hawk and Carbotech specific for the 2.5i system. Braided SS lines from the GT are able to be swapped in as well to stiffen pedal feel. Additionally there is a Wilwood and RacingBrake kit out specific for the 2.5i that swaps the front calipers and rotors.

 

edit: Ion Performance has now released a slim 4-pot performance brake caliper which is compatible with the 2.5i and will fit with OEM wheels or other 17" applications

http://www.legacygt.com/forums/showthread.php?t=121599

 

6) Transmission

The clutch for the 5MT in the 2.5i is not interchangeable with clutch types from the LGT. Thanks to research from members here, we have found that Exedy offers an aftermarket clutch compatible with the 2.5i 5MT transmission.

 

KSB04 is an Exedy OEM replacement

15801 is product number for the Exedy Stage 1 clutch kit (rated to 196lb-ft torque)

FF02 is model number for the Exedy lightweight flywheel.

 

We have also found that the 08 GT rear limited slip differential is compatible with the 2.5i manual transmission and this has been successfully mated to take advantage of the performance and safety gains vs the open diff on the stock setup. The 05-07 5MT rear differential is also theoretically compatible with the 4EAT transmission as the ratios are the same at 4.111:1 but this has not been attempted on any cars yet.

 

7) Exterior

LGT and 2.5i share a common exterior shell with noticeable difference being the 2.5i does not have a hoodscoop as we do not feature a top-mounted intercooler for a turbo. Thus installing a hoodscoop would not really be of any benefit to your engine. Additionally the 2.5i hoods are aluminum like the GT hoods, therefore there wouldn't really be any weight savings from swapping hoods (or swapping to CF). However, if you are interested in aftermarket lips spoilers or JDM conversions, these will fit and bolt right up.

 

Additionally the wheel sizes are the same at 17x7 with a 5x100 bolt pattern and +53 offset from the factory, earlier models ca 2005/06 came with 16" OEM wheels occasionally but aftermarket wheels for LGT in 5x100 pattern will be fine for all models; generally recommended you stay around +48 offset or higher for correct fitment, but lower offset can be done with some fender modifications.

 

8) Engine cont'd - “But I REALLY want to increase the power on my car, WHAT CAN I DO???”

AVO Japan has kindly been working on a low PSI turbo kit for our vehicles. The design is based of the kit that they have provided for Impreza 2.5 owners the past and has been installed successfully in many applications.

 

see link below for install on AVOs outback test bed:

http://legacygt.com/forums/showthread.php/avo-turbokit-install-146784.html

 

as of 3/25/2011 the kits have been manufactured and shipped for the 2.5i, please visit AVO's website for more information:

http://www.avoturboworld.com/avoshop/turbokit-deposit-p-111.html

 

as of 5/2011 members on this board have officially installed the turbokit on their vehicles, in particular member 1stick3pedals' thread has some useful information on the install:

http://legacygt.com/forums/showthread.php/avo-turbo-kit-1000-miles-later-162583.html

 

Additionally there have been reports that an Accessport (for engine tuning) is available for the Legacy 2.5i now, though at this time we still await testing of the product by one of our members.

 

Rallitek has also put out an aftermarket camshaft kit for the 2.5i which supposedly can create gains of 20hp (crank, I believe). A tune and use of their valve spring kit when installing these is highly recommended (ie. necessary)

 

http://www.rallitek.com/raca062.html

 

Rallitek does offer some other internal components that can allow the hardcore 2.5i enthusiast to really build up their motor. For most applications, I would suggest sticking with what has been laid out in points 1-6 as those are all tried and reliable options from members here.

 

But for more information on internals, one member here has posted logs and additional information here in this thread:

http://legacygt.com/forums/showthread.php/2007-2-5i-cams-exhaust-intake-etc-155249.html

 

---

Hopefully this guide will serve as a basic map for new 2.5i owners coming to this board. I have put together this guide based on some of my experiences in modifying my vehicle. There may some editing that will be required, since I don’t know EVERYTHING but I’m hoping fellow members can chip in as the guide is really a summary of the collective experience of 2.5i owners on here who have tried many things and have discussed many aftermarket components and issues re: them. So thank you to everyone who has contributed to the N/A section over time and LGT.com as a great place for all this information.

 

Also special thanks to N.sane for helping contribute to the FAQ

 

Special thread of note: Paul Hansen from AVO has documented a number of installs / repairs on their project outback, very useful thread with excellent walkthroughs and tips.

LINK HERE --> http://legacygt.com/forums/showthread.php/avo-project-outback-part-1-140263.html

http://alltheragefaces.com/img/faces/jpg/misc-seriously.jpg

If noone was aware, when I had my phenolic intake spacers the temp difference was drastic. I measured every runner, from center of intake to head mating surface with my pyrometer. the temp change was 30 degrees before to after. Make sure you are aware though that if going with 8mm spacers, you will need to tweak the EGR tube. I wasn't keeping track of gas mileage after every mod, but with panel filter, turbo manifold, resonator delete, OBX mufflers, lowering springs and even rolling on 245/35R18 tires I managed to squeak out 506 miles from one tank of gas.

506 miles?!!?!

 

i get like 400 at best

 

edit: lol @ N.sane's post

Damn you guys and your highway mileage. However, city mileage is actually quite decent with these cars, considering they're heavy and AWD. I can get about 310 miles (500km) from a full tank until the gas light illuminates. Highway driving probably only happens twice a month.

usually i'm around 350 when i fill up

 

400 is a stretch

506 miles?!!?!

 

i get like 400 at best

 

edit: lol @ N.sane's post

 

 

my driving was approx. 85/15 hwy/city. google "hypermiling"....you'll see why.

I've been getting <300 miles before the light. I remember I got ~360 miles one time riding the light until the last tick and I gave in and filled up. Turned out I still had ~2 gallons in the tank.

 

I haz a lead foot.

Hey guys, i own a n/a 2000 liberty/lagacy rx 2.5.

when ever i give her full throttle in say 2nd, 3rd and even 4th when it reaches 3500/4500 rpms it just stays there and wont accel till i slowly let the throtttle off but when i give it half throttle till redline it doesnt effect it. any ideas to what might be the cause? its also got a new fuel pump, coilpac and new plugs

thanx

Hey guys, i own a n/a 2000 liberty/lagacy rx 2.5.

when ever i give her full throttle in say 2nd, 3rd and even 4th when it reaches 3500/4500 rpms it just stays there and wont accel till i slowly let the throtttle off but when i give it half throttle till redline it doesnt effect it. any ideas to what might be the cause? its also got a new fuel pump, coilpac and new plugs

thanx

 

Possibly your clutch

Damn guys, the furthest I've gone is 350 miles on one tank. I thought I was a baws, guess not...

Damn you guys and your 2.5i gas mileage.....

 

I sold my car a few months ago, I've been meaning to post some pics of the new ride, but my camera is busted.

Well look who it is, traitor! How are you enjoying your torque steer?

Damn you guys and your 2.5i gas mileage.....

 

I sold my car a few months ago, I've been meaning to post some pics of the new ride, but my camera is busted.

 

Sold the RS header as well

I copied and pasted this from the come in if you are N/A thread:

 

I made an interesting discovery recently after getting my diff fluid changed at an independent Subaru shop. The owner was nice/curious enough to plug-in his Open Source software to check the IAM (Ignition Advance Multiplier) of my car, something that's not really discussed much with the 2.5i.

 

Without getting too detailed, the IAM value will range from 0-16 (increments of 4) on older Subarus, and 0.00-1.00 (increments of 0.25) on newer Subarus. The higher the value, the better (engine is knock-free and running efficiently).

 

My initial value was 0.50, so the shop owner suggested I run premium fuel on my next tank of gas, so I did. I've used a full tank of premium now, and I can definitely say that the engine runs smoother and feels more potent (feels like I restored lost power; inclines that usually required a downshift is no longer needed; acceleration is noticeably stronger) and my gas mileage has also improved during my daily drive to work. I went back to the shop to check the IAM value again and it's now at 1.00, so the car is definitely "happier" and operating at the ideal IAM.

 

The funny thing is, in Europe and Australia (and probably Japan), the Legacy 2.0i/2.5i is recommended to take 95 RON, which is equivalent to 91 octane. It seems SOA thinks recommending regular fuel for the N/A cars will help them sell more cars to customers who want to save money at the pumps? I compared receipts, and it's only an $8 increase for about 50 litres (13.2 gallons) between 87 and 94 octane. However, the cost difference will be offset by the extra distance you'll drive from the better gas mileage.

 

My 2.5i brethren, I encourage you to get your IAM checked out and bring it to an optimal figure if it isn't optimal already. You'll love the difference.

I guess I should add a couple of things:

 

1) IAM isn't just affected by your fuel grade. I think anything that affects the combustion cycle is a factor i.e. spark plugs.

 

2) About halfway through the fresh tank of premium, he suggested resetting the ECU. This can be achieved by disconnecting the battery and then stepping on the brake for several seconds so the 3rd brake light drains any remaining juice.