FAQ: Subaru Legacy 2.5i

Wow, it's been a while since I've seen those photos lol. You have a GTO now? Dafuq?! What happened to the Spec.B?

I sold it. Engine out 5 times, trans out once, $20k in repairs/mods. just had enough with worrying about the next problem. Figured going with my roots (V8 RWD), would be able to take more power with minor work. 400HP is a nice starting point, and if I add boost, the internals won't be falling apart until over at least 500 wheel. add in the same monthly insurance payment, saving $140/month on the payment, also a rare car, and 41k miles when I got it........yeah!

^ that doesn't sound like the spec B dream i'd like to have...

 

congrats on the GTO though.

more like 5 nightmares with some fun in between. I saved at least 10 grand in labor doing everything myself, but I still wasn't looking forward to the next issue.

more like 5 nightmares with some fun in between. I saved at least 10 grand in labor doing everything myself, but I still wasn't looking forward to the next issue.

 

Maybe if you stayed stock these problems wouldnt exist, Mr. Cool-ster :lol:

 

What ive learned over the years and posts from LGT owners is that I dont really want any mods.

Stay stock? haha never!!!

I already got a new intake, short throw shifter, catless mid pipes, and stainless works 3" catback on the goat. Vengeance racing VXR5 cam to come soon. maybe CTS-V calipers and some VMR V721 or TSW Mallory 19's. we'll see......

I love the GTO's people never respected them when they were in production and still dont now they are night walkers lol. I would love to pick one up and throw on a exhaust and call it a evening.

I totally agree it's an underrated car.

great write up thank you.

 

If you're on stock suspension and don't do much hard driving, I would go 17x7 or 17x7.5 with an offset that's at least +45. With these wheel sizes, the following tire sizes are the most suitable and the descriptions are my opinion of what they offer:

 

205/50/17: Most fuel efficient; however, you get the least curb protection for your wheels and will have the least grip of the group. Diameter is close to the stock 205/55/16, so gearing won't be effected. I would only recommend this as a winter size on a 17x7 since narrower is better for snow/ice. However, I'm guessing you would use your stock 16's for winter.

 

215/45/17: Best overall performance size for 17x7. Improved acceleration since the diameter is slightly smaller than stock, creating the effect of shorter gearing. Easier acceleration maintains fuel efficiency. You also get sharper steering response since there's less sidewall, and as a result, a slightly less comfortable ride. I use this size personally on my 17x7 since I value performance over comfort.

 

225/45/17: Best overall performance size for 17x7.5; the widest that's recommended for 17x7. It will give you more overall grip than the 215/45, but on a 17x7, you'll sacrifice a little steering response but maintain ride comfort. The wider contact patch may decrease gas mileage slightly. Diameter is close to the stock 205/55/16, so gearing won't be effected.

 

235/45/17: The widest that's recommended for 17x7.5. May give you a little more overall grip than the 225/45, but you'll sacrifice steering response. The wider contact patch, larger diameter, and increased weight will decrease acceleration performance and fuel efficiency, but will give the best ride comfort.

 

Cliff Notes for 17x7

 

205/50/17 - fuel efficient and comfort, but with the least grip and curb protection

215/45/17 - fuel efficient with good steering response and improved acceleration, but less comfort

225/45/17 - best overall grip and comfort and most curb protection, but less steering response

 

Cliff Notes for 17x7.5

 

205/50/17 - fuel efficient and comfort, but with the least grip and curb protection

215/45/17 - fuel efficient with sharp steering response and improved acceleration, but less comfort

225/45/17 - good steering response, overall grip, and comfort

235/45/17 - sloppy steering response and least fuel efficient, but most comfortable and most curb protection

Just the info I needed. Thanks for this write up. Even though its 4 years old.

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

 

So I was looking on the grim speed website at the intake manifold 8mm spacers do they actually fit on a 09 2.5i only thing I was seeing was for a lgt does the n/a 2.5i and the lgt do they have the same intake manifold that I could get the 8mm spacer for my 09 2.5i

So I was looking on the grim speed website at the intake manifold 8mm spacers do they actually fit on a 09 2.5i only thing I was seeing was for a lgt does the n/a 2.5i and the lgt do they have the same intake manifold that I could get the 8mm spacer for my 09 2.5i

 

I've got a 2005 2.5i legacy and I have 3mm spacers which were from a wrx and they fit fine. The bolt holes all lined up, but the holes for the studs did not, those don't matter anyway. Assuming you have the same intake manifold as me, the LGT ones should fit. Only way to be 100% sure is to go to the dealership and just ask to see an intake manifold gasket for your car and an LGT, see if they match up. If you want the 8mm spacers, you will need to have your egr pipe modified in some way. I stretched mine out since I only had 3mm spacers, but you'll probably have to either extend your's or just cut it in half and weld both sides shut.

After looking under the hood of my car I have come to the conclusion that the #017001 spacers are the correct fit for our cars despite the Grimspeed site saying it only fits up to 2006 Legacy N/A. The shape, bolt holes, and stud holes are all identical to our gaskets. These will be installed on my car along with the AVO kit and more goodies next month! Coming from someone who works closely with high heat, steel, and aluminum I believe this to be a simple yet effective solution to reducing heat transfer to the incoming charge air!

I saw this thread a while back and was thinking of getting the cams from rallitek, but now they don't sell them. Has anyone seen a different set, or know if the ralliteks are available anywhere?

Does anyone know if any wrx flywheels would fit an07 2.5i?

Quick question is like to get the light weight crank pulley but then I'd also like to get the ntb throttle controller if I'd get both of them would it matter seeing how the both boost the acceleration rate? Or should I get one or the other?

Euro what gaskets are you talking about, intake manifold gasket?

 

 

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Does anyone know if any wrx flywheels would fit an07 2.5i?

 

Yes 06+ WRX is the same for Legacy (N/A and GT)

Quick question is like to get the light weight crank pulley but then I'd also like to get the ntb throttle controller if I'd get both of them would it matter seeing how the both boost the acceleration rate? Or should I get one or the other?

 

Both of those are great 2.5i performance mods. Only the light weight crank pulley is actually going add some power. It might not even be a noticeable amount (Perrin told me 4-7 hp), but it will rev quicker which is useful if you drive a manual. The throttle controller will have no affect on the engine's power, but instead the throttle responsiveness will be a lot better and you can adjust the throttle behavior with a simple press of a button. So if you're in an econ mode and you're flooring it, your car will feel a lot slower because the throttle controller is saving you gas. But if you're in a sport mode, just tapping the throttle will make it feel like a race car, although in reality it's no different than WOT without the controller.

 

As a former 2.5i owner who had both of these mods, I'd say if you had to choose one, go with the throttle controller. It won't actually add power, but it completely changes how your car feels. The crank pulley is also a good bang for your buck power mod that will add more hp, but it's not gonna be as noticeable of a difference overall. Basically your choosing between feeling a lot faster, or actually being just a little bit faster.

Kred are those all the mods you had on your 2.5i or are there more? Did you have the throttle controller on just to save gas or would it be the same as just without one

 

 

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I got the throttle controller mainly for a sportier/ more responsive throttle feel. If anything my gas mileage got worse because of the way I started driving with it, lol. But it can save you gas if you can bare with the sluggishness of econ mode. I also had a high flow intake panel and phenolic spacers which probably didn't really do much. Catless header back exhaust made the biggest difference.

Kred the reason o asked is cause I was going to get both of them just I didn't know if it work right but I'm guessing if I do get both of those that it won't matter at all?

Oh and I'd also like to say that I'm getting the nameless Axel back just waiting on it to be shipped and this week I plan on doing the hybrid intake and I have the aem dry filter in it now

Ok, if money's not an issue, I'd say get the throttle controller and crank pulley. They'll work great together. The hybrid intake is a smart move, but I upgraded to a GT before I got around to that. Edited May 5, 2014 by kred