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Hello I have a question I have been pondering...if a N/A impreza has 170 HP @ the fly is there a way for it to gain 30 extra HP with just bolt ons, no turbo.
 

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that sounds like a pretty realistic goal, um i would start with equal length headers(lose the boxer rumble but better flow), 2.5in exhaust, a cold air intake, and a reflash, then see what that yields. after that it could possibly get a little more extreme with the difficulty of the mods
 

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that sounds like a pretty realistic goal, um i would start with equal length headers(lose the boxer rumble but better flow), 2.5in exhaust, a cold air intake, and a reflash, then see what that yields. after that it could possibly get a little more extreme with the difficulty of the mods
from my understanding the N/A impreza already has equal length headers. and i know mine sure doesnt have the boxer rumble. id probably be a little bit happier if it did
 

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The usual boltons will get you around 30. Intake, headers, exhaust, tune. If all else fails you can always spray
 

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Oh yeah, 30 extra crank horsepower COULD be possible. Equal length headers/hi-flow cat...2.25 to 2.5 inch exhaust, cold air intake, Perfect power 6 and tune....you might be a little short though. It depends how good the tune is and how well all the parts mesh together.
 

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okay that would be a little bit costy but wouldn't swapping the 2.5 SOHC head with the 2.5 DOHC WRX heads add hp?? (ok including the complete tune needed and everything needed)
 

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okay that would be a little bit costy but wouldn't swapping the 2.5 SOHC head with the 2.5 DOHC WRX heads add hp?? (ok including the complete tune needed and everything needed)
Not really, if you were to swap wrx heads, power gains would be mediocre at best. Subarus aren't like hondas, you can't gain insane numbers from just swapping heads. The work you'd need to put into it to get good power wouldn't be the effort.

The 1998 impreza RS had a DOHC 2.5L NA engine, it made like 160 hp...the 99-01 RS with a SOHC 2.5L NA engine made 165 :p
(SOHC is not necessarily < DOHC)...and the new SOHC NA engine in the 08 makes 175 (thanks to AVLS).

I guess someone could try swapping heads, but I think the time, effort, and money to do it would be than just doing simple bolt-on mods.
 

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thanks buddy the question was just stuck there in my head not that I have the means to pay for that kind of swap anyway, MAN I sure hope they release a N/A Cai soon, I'll go for the K&N filter while waiting
 

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What about adding a lightweight pulley to that equation?
A lightweight pulley won't add any extra horsepower. What it will do is free up some of the power that is going into building rotational momentum in the pulley. It takes less energy to get a 1 lb. pulley rotating from still to 3000 rpm than it does to get a 6 lb. pulley rotating at the same speed. So, the pulley won't give you more power overall - your top speed will be the same, etc. However, acceleration will be slightly quicker, as the engine will rev in a shorter period of time.
 

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What about adding a lightweight pulley to that equation?
A lightweight pulley won't add any extra horsepower. What it will do is free up some of the power that is going into building rotational momentum in the pulley. It takes less energy to get a 1 lb. pulley rotating from still to 3000 rpm than it does to get a 6 lb. pulley rotating at the same speed. So, the pulley won't give you more power overall - your top speed will be the same, etc. However, acceleration will be slightly quicker, as the engine will rev in a shorter period of time.
sounds like nice anyway who really needs to have a faster top speed anywayz??? but better accels and/or probably a better fuel effiency why not eh!! I'm thinking of ways to lighten her up a bit now the back seats are probably gonna disapear ;)
 

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[/quote]

A lightweight pulley won't add any extra horsepower. What it will do is free up some of the power that is going into building rotational momentum in the pulley. It takes less energy to get a 1 lb. pulley rotating from still to 3000 rpm than it does to get a 6 lb. pulley rotating at the same speed. So, the pulley won't give you more power overall - your top speed will be the same, etc. However, acceleration will be slightly quicker, as the engine will rev in a shorter period of time.
[/quote]

Thanks for elaborating on that...although I was fully aware of that fact...it will mimic the effect of having extra HP ;D
 
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