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Discussion Starter #1
I just recently bought a 2001 Subaru Impreza 2.5rs. It’s the first car I have owned unless you count the junker my father let me use. I’m very new to the world of cars, and I’d like to use this car to learn. My main goals are as follows:

-Switch out the 5-speed for a 6-speed,
-Twin Turbo and NOS,
-Aim for 900 HP,

At the end of the day, I want the car to get up to speed quickly, and be able to handle the steep curves and hills, while still functioning as my day to day car.
Unfortunately, most of my research has been unfruitful. The information is either over 15 years old and potentially out of date, or just not helpful. Usually, the thread is: telling people to buy a new car (I specifically want the gen 1, so a new car is pointless to me), broken links, conflicting information, or telling people to go to older posts with the aforementioned issues.

Bottom line:
-Do I need an engine swap? From what I understand, both my car and the STi are EJ25. Could my current engine handle my goals, even if it meant more work?
- CAI? Some people say they’re great, some people say they’re more harm than good. Personally, I like the sound of a cold air intake, and standing water isn’t usually something I run into, is there something weird about Impreza’s that they have different issues with CAI than other cars? Or do people just have issues with CAI in general?
-With or without an engine swap, what else do I need to do to my engine to achieve my goals?

P.S. I’m aware it will be an expensive and time consuming project, but I’d rather spend the time and money than cutting corners and running into issues.

I also already have plans for the brakes, tires/wheels, body, suspension, etc. I mostly just need help with the engine
 

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It wouldn't take much research to uncover the differences between your motor and an STI motor. I know for a fact there are still threads about it around. Regardless, no your motor will not come close.

I don't think you understand how expensive it's gonna be. You're gonna need DEEP pockets to reach your goals, but it can be done.

You have an ej251, the STI has an ej257. Even the STI motor will need to be seriously built to handle 900 HP. Start with the 6 speed swap, that'll introduce you to cars and learning to work on them, including how to research to find the info you need.

 

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2000 RSTi
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Buy a R35 GTR and be done with it.

You won't make 900hp reliably from the EJ/FA platform.

You might make 650whp reliably with $30k spent on just the engine and turbo setup. But the 6-speed won't hold that (for long).
 
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Discussion Starter #4
I’ll definitely look into the 6-speed swap first if that’s a good start, and from my understanding, the EJ251 and the EJ257 were both marked as EJ25, and that’s why I was confused.


As far as buying an R35, I’d love to own a R34 (I’m not too big of a fan of the modern look of the R35), but getting parts if something goes wrong is usually easier for a Subaru. Do you believe 600whp would be a more reasonable goal then? And what do you mean the 6-speed wouldn’t hold it?
 

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I have to say, everything I've read suggests that the 6 speed is freaking sturdy. Andy Forrest was using one behind a 1200 hp EG33, not kindly.

600 whp is about the long term goal for my LGT. It's about to get a built 2.2L and a GT35, and I'm just shooting for 400-450 whp for now. That's about as good as you can do while balancing budget and power.
 

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If you launch with 600whp, it will break eventually.
 

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Discussion Starter #9
I don’t really know any alternatives to NOS, I just figured if they’re so well known, they probably work pretty well. Are there better alternatives for a Impreza?
 

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-Twin Turbo and NOS
-Aim for 900 HP

I’m surprised there is much information out there at all on these two topics, let alone conflicting information. Maybe one of the short block manufacturers could point you in the direction of a builder?
 

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‘98 RS, 911 Cab, CT6 TT, Escalade ESV
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The most reliable and fairly cost effective way to have a 900HP subaru would be to put an LS-platform engine in it. It'll cost less than half as much as a hyper-built EJ25 setup and you can throw all the twin turbo and NOS your heart desires. If it breaks, pick up another iron block for $300 and dump it in.
 

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" At the end of the day, I want the car to get up to speed quickly, and be able to handle the steep curves and hills, while still functioning as my day to day car. "
If these abilities are what you're aspiring towards, there is no way you need 900 HP - I have driven cars rated at 450-500 HP. The power these cars were yielding were fucking insane! There is no way a car even approaching these power levels is going to be a daily driven car. I daily drove a 2 L WRX making 298 WHP on a Mustang dyno. This car was more than enough for ripping through autocross events and absolutely shredding the hilly terrain in my area...with authority. There is sooooo much more you need to address in addition to a motor that will get you anywhere near those power levels - suspension, tires, brakes, chassis bracing, a drive line that will support that type of power. This is just a suggestion, but why don't you think big and start small. Get to know your new car, as you stated, this is your first car. Sign up in and run some local autocross events, focus on handling, ie: tires, braking, and suspension upgrades and then focus on engine and power upgrades.

" Bottom line:
-Do I need an engine swap? From what I understand, both my car and the STi are EJ25. Could my current engine handle my goals, even if it meant more work?
- CAI? Some people say they’re great, some people say they’re more harm than good. Personally, I like the sound of a cold air intake, and standing water isn’t usually something I run into, is there something weird about Impreza’s that they have different issues with CAI than other cars? Or do people just have issues with CAI in general?
-With or without an engine swap, what else do I need to do to my engine to achieve my goals? "
I'm not trying to come off as asshole here, but if you're having trouble answering these questions, you're probably not anywhere near having the capacity of building or driving a car of the magnitude to which you aspire. There is a shit ton of great information on high horsepower builds, as well as the pros and cons of building such a vehicle. You have a solid platform on which to build a great car if that's what you want. Just slow your roll a bit and put the time in for the research - not just internet research, I'm talking real world research on the dynamics of your ride. Get to know her a bit first before you make any decisions. Just a suggestion...
 

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Discussion Starter #14
A newer car can get around 500hp off the lot, and I have no problem putting newer components in the car I have if it isn’t going to need modifications to the body. But if newer cars can come off the lot with 500hp, why would that be too high for a daily drive? And would the previous post about shooting closer to 600hp be better for my goals? This isn’t something I plan on having done overnight, I have full intentions of doing upgrades over the years, and as I stated in the original post, I already have plans for tires/wheels, suspension, brakes, etc. I just don’t know what’s a good engine to build up in a Subaru.
 

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There is really no compensating for displacement. You can do whatever you want to a 2.5 liter motor, but it will never make the same power if you put it up against a 5 liter with equivalent modifications. At some point, the displacement prevents you from making easy/reliable horsepower, deep pockets or not. The age is really irrelevant, and the factory cars to which you are referring, at 2.5ish liters, typically make somewhere between 300-380 at the crank, stock. These cars also typically weigh anywhere from 300-700lbs more than a stock GC8, so 350 HP in your GC8 is going to feel much different than 350 HP in a "modern" car. The factory 500 HP motors are typically coming from 6 or 8 cylinders that usually are at least 50 percent larger than the stock RS motor.

In terms of reliability, again, you are looking at a platform that was designed for a relatively light-weight car with a medium sized four-cylinder engine. Anything that is going to bolt on easily was designed with this in mind. 600 WHP is going to be taxing for any drivetrain, so as a daily driver, that much power may even be unreasonable. If you do it right, is it going to be a glass cannon? No. Is there a higher chance that you don't make it to the grocery store? Absolutely.

And, in the end, I would be willing to bet that if you drove a Mazda Miata and a Chevy Camaro LT1 for a week each, you would pick the Miata without question, even though it has almost 300 less HP. I think what everyone is trying to point out is that the GC platform was not designed for ridiculous horsepower numbers and that the enjoyment of the car comes from its handling and the zippiness that comes from not being built on a modern, bloated platform. 900 HP? Probably unlikely. 600 HP? Possibly. If you got 300 HP to the wheels with the handling modifications you mentioned, I think you would be very happy.

With all of that said, I want to make sure I second the suggestion that you call some places to see what is possible in terms of HP and what path you should take to reach the goal that you are finally set upon. You just had a bunch of the most knowledge people about Subarus express their skepticism about your goals, people who have owned many, many Subarus in various forms. These aren’t cranky old men who don’t want the kids skateboarding on the sidewalk; these are people who are going to encourage you to reach your goals but won’t sugarcoat something if it is unreasonable.
 

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OP, your thread is so stupid I actually went out of my way to make an account (on a garbage 3g connection) just to make fun of you. Judging by your forum name you're a weeaboo and it made these "how much does a rock weigh" questions you're asking make a lot more sense. From the sounds of things before you dump any money into that poor RS perhaps buy a mid 90s Camry and drive it without wearing your seatbelt for a while. You don't sound like someone who could handle close to 900 horsepower much less the 160 the RS makes. Everyone reading this thread is now dumber because of you.
 

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Congrats on your first car, OP. One of the most challenging things starting out (not just cars but formal education and even daily life) is navigating the wealth of information that's available to you. Much of what you read on any forum is conjuncture or opinion. Your goals will change and evolve the more you learn and you will become more efficient at sourcing information. Take the time to read and learn as much as possible before you make any decisions and reduce the risk of wasting money. Always defer to the Subaru maintenance manuals when possible (written by engineers), rather than the opinion of random people on forums. There was a lot of good advice above and now it's likely you've already adjusted your expectations of the RS. Don't be discouraged, keep learning, and pay it forward by being respectful to the newbies and add value to their journey, not negativity.

I also recently bought a 2001 RS from someone who clearly did not know how to maintain a car. It's incredible the damage and neglect on my vehicle that I'm slowly uncovering. My time is mostly spent inspecting and trying to source oem components when possible to restore the car to near stock. These cars are so rare that's it's truly a shame to see some of them destroyed and tastelessly modded. I would suggest initial focus on basic car maintenance like how to change oil/fluids and brakes, etc.
 

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Discussion Starter #18
Congratulations on your account Bratt! Since you took interest in my username, it comes from a dirivative of a nickname, my love of the sky, and my love of archery, and it’s unique so I can use it on practically every website without issue. I specifically chose the car I did because I like the boxy shape of 90s Japanese compact cars, and the car I bought was in excellent shape for $3,000.

As for the rest of you, thanks for the help, and I’ll probably start with an engine and transmission swap from an STi, and go from there.
 

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He should've gone with 'mr hanky' for a username.
 
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