How to upgrade a '07 Subaru Impreza 2.5i NON WRX???

Asked by Sep 27, 2009 at 02:24 PM about the 2007 Subaru Impreza 2.5 i

Question type: Car Customization

I am looking to make my car faster. Thus far, I have done some simple things like upgrade the air filter to a K&N, I've tinted the windows because I live in AZ and it's hot as hell here. I've upgraded the stereo and I got some good street tires. I'm ready to start adding things under the good and I am willing to spend but am unsure about turbo charging the 2.5i as it is 10:1 compression. The WRX is 8.4:1 compression because it is turbo charged (I am guessing here), and the STI is 8.2:1 compression (confirmed from the Subaru Website). Could I only put a small turbo on my car to reduce risk of running the engine into the ground before it should...?? Any help/info would be great. I wanna beat STI's, but I wanna do it with some good knowledge and research behind it. I'd love to hear about anything to improve the car's performance from weight reduction to computer chips. Thanks for all the help. :)

34 Answers


Sell the 2.5i and buy a wrx, thats how you upgrade it. 2.5i's will not be fast unless you swap it, I am sorry to say. In the long run it will be WAYYYY cheaper to just get a car that is designed to be turbo'd

3 people found this helpful.

i ran a t3/t4 turbo with stock injectors on a 2000 2.5 rs. It would have been safe if i kept the boost low, but everybody likes the idea of turning a knob and going a little faster. i kept turning the boost up until i put a hole in the number four piston. if you do turbo it, get a nice wideband o2 sensor. read up on how much boost people have been running on your engine. After you buy the turbo, up pipe, down pipe , exhaust, wastegate, fuel pump, intercooler, blow off valve, boost gauge, and still have to worry about management, and possibly larger injectors. Do all of this and your car will be a little faster, you can probably run 5 or 6 psi. and with the higher compression get around 230hp whick is still slow and you will not be happy. I think that your best bet would be an sti engine swap. the internals on the stock sti block are supposed to be good for up to 400hp. Check if your wiring harness will work with the sti engine. do you have variable valve timing? i know the 07 wrx and sti do. the 06-07 WRX block ej2507 is the same as the sti block. it is really just a bunch of research...and then deciding how much you want to spend and how fast you want to go. plan on spending at least 2k for simple turbo add on. or 4k for sti swap. but then you have the weak transmission to deal with. haha. good luck!!!

5 people found this helpful.

yes, but in the long run, it will be far cheaper and way easier to get a car that starts out a lot faster and is built to handle the higher levels of performance. I stick with my thought to sell it and buy a wrx or try to find a lower mileage 04/05 sti, those are about as much as a newer wrx, and you get the best tranny that subaru makes in the process. But to each his own, in the end you make the decision of what to do

1 people found this helpful.

and also, the engine used in 2000 is far different than the one used now in the 07 non turbo imprezas, and it is not uncommon to see turbocharged GC8 imprezas that have been modified

Thanks so much for the responses. I don't know if I have variable valve timing but I can see that my best bet is to either do an STI engine/tranny swap or simply to upgrade to a newer Impreza. I'll update when I do make a decision. Thanks again for all the help!


it doesnt necessarily have to be a newer one, just keep that in mind. You can find plenty of low mileage older ones that will be just as fast. One thing to keep in mind is that the 06-07 wrx does have the 2.5 turbo, which has a much better power potential than the 2.0 turbo. But as a platform, why not start with the best? I would try to find a used sti to work with, or something that has already been swapped, unless you plan on doing the swap yourself? You will be saved a lot of time money and headaches that way. But always happy to help a fellow suby owner


Be aware, you are not going to reliably 'beat STi's' with bolt on forced induction for this car. Kits, range anywhere from 2k to 5k, and for that price, you might as well spend another 5k on top of it and do a Sti engine swap - or sell it and buy a used WRX or STi.. it would be cheaper in the long run methinks. My suggestion is, quit thinking in straight lines, because that is not what these cars are about. I'd grab a set of Lowering springs, and upgrade the brakes, sways, links, add some strut bars and fender braces. Those mods alone would have you performing very well on the track, even vs. those high compression big turbo'ed STi's. Good Luck and I Love the Wagon, and that Color!!

3 people found this helpful.

I would trade the 07 non wrx in and buy a wrx sti. this way you dont have to worry about swapping engines or different parts for different turbos or putting unwanted holes in anything. im currently in the process of trading in my 97 subaru legacy outback in for a 2002 wrx sti bugeye in yellow!!


In all honesty, lowering a subaru is not what these cars are all about either. I mean mine is lowered but if you really want to get technical about it subarus are meant to be driven offroad. Hence the name wrx, i mean it stands for world rally cross country. And they did not even begin importing the sti into the united states until 2004 so unless you are picking one up from japan the title will state only WRX. I still stand by my advice to ditch the 2.5i and get a wrx. My 07 wrx has the VF39 turbo and a bunch of other parts with a protune and I can hang with stage 2 Sti's. If you really want some good advice check out the forums, or That is how I learned a lot of what I know


what about forging the pistons and etc? even putting a full exhaust system gives you a boost in hp, the only way im guessing to beat an STI is to have one or there i say it an EVO

2 people found this helpful.

I never said it couldnt be done, it would just be better on all fronts, (cost, ease, reliability) to just trade the car out. And in a non turbo, small engined vehicle, intake and exhaust gains are minimal at best.


Here is a thread about eeking 300HP out of a Modern N/A Subaru Engine. As you can imagine, this is no shade tree modification.

6 people found this helpful.

i love my 07 2.5i (AT) Impreza wagon. has been garaged for the last year (60kmiles). people dnt see anything in this car, an STI is so obvious. My goal is to one day do a complete power-train swap (motor+trans) as well as a complete swap of all running gear (suspension components,breaks,cooling systems, fuel systems, computer and software upgrades.) all in the cover of a 2.5i wagon. A wagon. our whips are twins dude i got tints just as dark, live in MA cnt get a sticker hahaa

3 people found this helpful.

Sell it and buy the Ford Focus ST. 250hp turbocharged car with a curb weight under 2600LBS and a full rally suspension for around $25k. BYE BYE STI

1 people found this helpful.

too bad it's a FWD and a ford, I wouldn't trust em you can buy a new WRX with about 15-20 more horsepower and AWD for about $2k more if you bought brand new if you got 1 a couple years used it'd be cheaper.

2 people found this helpful.

Ford has higher reliability ratings than Subaru, and 15 hp doesnt make up for 600 lbs of body fat. Not by a long shot. As for AWD, thats negligible. To boot this is the ST model, not the RS model, the RS has 304 HP and the RS 500 has 350.

1 people found this helpful.

well as a mechanic I wouldn't trust any Ford Focus's, some Fords are good but their high reliability rating is not caused by their Focus.

4 people found this helpful.

I have a 2008 subaru impreza 2.5i and the thing with a turbo is you definitly need racing pistons (it's arround 700$). You might need a manifold and a crankshaft too. I would tell you to buy racing chips before putting a turbo in your car because it's more worth it (price for power) to add a turbo you need AT LEAST 1500$ + the turbo kit (3000$)= 4500$(at least). Maybe there is a turbo that could fit in the 2.5i but i've looked arround and I haven't found one. The WRX can handle atleast 25psi turbo (my friend have the WRX and he put a 24psi in it) so maybe with all the upgrades you could add a good 15-20 lbs turbo in your 2.5i. The best thing to do is to ask your mecanic. or ask a subaru dealer ship or to go to a performance shop. For more power, i would say to add an exhaust (8 hp) to make the flow better. You can add a stage 2-3 clutch to shift faster (1200$ - 1500$ w/installation), short shifter, fuel injecters (maybe i'm not sure), better radiater (if you are not adding a turbo because turbo kits usually comes with a rad..), transmition stage 2-3... You can also add a carbon fiber hood, spoiler, trunk, even a bodykit (just make sure it's not a wide kit or else it wont fit). Every thing is possible, it all depends of how much money you are willing to spend. Hope this help.

1 people found this helpful.

if u want to reduce the weight try to replace ur hood of the car with a light composite metal or material also u if have a flywheel get that replaced with again light weight also think about getting ur driveshaft that goes to the rear wheels done as well then comes the seating of the car those are alot of weight right there

1 people found this helpful.

You can make a 2.5i impreza look/sound just as good as an sti or wrx just tales time and money... Mine is a 2006 impreza 2.5i with 82,000 mi and about to be turboed


Hey jus thought i had to share these 3 videos with you, a little off topic but some ideas none the less. You may have already seen these 3 vids or heard the name "KEN BLOCK", but if not even better! Gotta love SUBARU, maybe you can get a lil inspiration! - "DC SHOES: KEN BLOCK GYMKHANA TWO BUILD" - "Best Car Drifting Ever" - "Best car drift ever"


i have a question i need help with. i have a 2007 subaru 2.5i non wrx, i bought it new basically all stock, i really dont consider a K&N air filter a big up grade but thats all i have. i have had nothing but problems since new. now i have 126000 miles all free way and cant afford the timing belt yet. i have used red line oil through out its whole life, now all my cats are out AGAIN. now i questioned the oil its not it. my question is my buddy has a highly modified 06 sti he still has the stock exhaust in his garage i know sti cat back will fit but will the down pipe back fit? i think that would be an up grade to just trying not to spend 1200 dollars to fix it

1 people found this helpful.

that exhaust will not fit on a naturally aspirated model

1 people found this helpful.

you put on a air intake not suited for the car, in which it blew out your cats because of the restriction of flow going to your exhuast... in other terms, you have to much air going in your engine and not enough going out

1 people found this helpful.

and if ou wanted to lower your subie, i suggest getting quality struts and springs, as well as a camber adj kit and new adjustable control arms, i did on my wagon and it rides soo smooth... but only a road car

1 people found this helpful.

idk what you guys are talking about when you say had your windows tinted afterwards. all 07 2.5i imprezza outback special editions came like that. as for reliability mine has almost 275000kms on it and still runs fine. but idk if my old engine would just die if i put a new forced induction system on it. don't think it could handle anymore than a new cold air intake and a small supercharger. only thing I've had to replace so far are both 02 sensors. and on a side note a friend of mine told me my bottom grille was missing. is it supposed to have a honeycomb in it or is it supposed to be open to your rad.


and when you say you want to be able to beat sti's are you talking in a 1/4 mile or on the track. because I've gone up against 04 sti's running 12psi and barely been pulled on when in 4th. so unless they upgraded their turbo it wouldn't take much as long as you hit your shifts. try shifting just before redline in 1st and 2nd then letting the only reach 55-5800rpm in 3rd and then just let her run in 4th

1 people found this helpful.

06-07 imprezas don't have a bottom grill, only the top three. As for trading cars in for an sti, you can't buy a stock sti wagon for the 06-07 imprezas (as far as I know). I plan on swapping my 06 impreza rs wagon. And get a 6speed tranny becaus I hate being at 2500 RPMs going 65 M/H. Definetly getting some serious coil overs, camber adjustment kit. And to have a true one of a kind look I'm going to get sti fenders, front bumper, and skirts, but keep the rs hood.

Get rid of it and buy a wrx or sti, I've already ignored everyone on that suggestions, and I paid the price of blowing 9k in jdm wrx swapping my subaru. Fucking wast of money and time, doing full jdm wiring swap from front to back. It's not worth it. Please just save yourself the time and pain and sell it.


I have done several mods to this 07 Impreza for my son, but if you want a sleeper that can run with STi's, I suggest you buy a used STi, swap the hood and deck lid, add a forward mounted intercooler and Voila! You have your Impreza Sleeper for a lot less!

3 people found this helpful.

OTOH the K&N is a great placebo, eh?! Your '07 already has the VVT upgraded motor introduced in '06. Chop off the muffler if you want your brain to think about speed.

Also, to note, if you want to put your car on boost and are really stuck on keeping the car, look into the e85 route. Its a bit complicated requiring an aftermarket ECU, flex fuel sensor, high capacity fuel pump and larger injectors to star. You should be able to run 8-13 maybe more psi of boost while keeping your engine relatively safe. If you are looking to go this route it is highly advised to take it to a professional tuner to retard timing and adjust fuel/air ratio and safe boost pressures. e85 is a great alternative to upgraded pistons, rods, cams and crank for turbo high compression engines. If you are quite set on keeping impreza.

Well my baby is a 2.5i adding a cold air intake is a bust. However by piping it with 3" exhausted behind the resonator and adding a straight outlet exhaust increased boost and sounds awesome. Then again it's the rider, not the ride that can't make the car go fast. Subiré has great control past 90mph


"Increased boost'? Are you kidding? All you did was increase sound...and maybe reduce torque too. Damned placebo effects....

1 people found this helpful.

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