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I have a 04 civic si ep3, I plan on doing a 70mm ebay exhaust with a 70mm invidia header, and a skunk2 intake manifold, I already have the k&n typhoon setup, what kind of a power increase do you guy think i should get

 
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I have decided to go with blackworks cat back exhaust

 
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10whp, if you're lucky.

You'd be better off doing a plethora of other things if your goal is to make power. A k20a/a2/z1 head would all offer significant gains.

 
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Seriously? I would think the intake manifold would add atleast 20-30 when the vtec kicks in

 
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GIS for the obvious:


and



/Go ahead and hate on me.
//LOL

 
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You said nothing about an intake manifold. Personally, idk what kind of gains you would get from one. Hopefully someone else knows, I'm curious.

Just exhaust and header, which like he said would prolly give you about 10whp. After adding those, a professional dyno tune would probably get you another 15-30whp and an increase in fuel effiency -- belive it or not. That will cost $400-$700, depending on who does it.

 
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Actually a skunk2 intake manifold was in the original post, I am trying to make this car fast naturally aspirated, and if I ever do boost it I want to have built the engine by than.

 
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Intake manifold alone without turbo? 10whp maybe? This is a crapshoot and everyone is guessing. If you want to know the answer do a dyno before install, install it, then do another dyno That way you know what you gained. You might not get anything.

 
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K engines are also very well designed to begin with.
I/E will not do much to them. heck, it's a 2 liter!
a higher displacement poorly designed with tons of restrictions engine will get easily more power with that mods, but it's a percentage game, not raw gains.

 
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You can't forget man, the k20a3 is fundamentally different and indeed inferior from any other k-series engine. Although, a k20a2/k24a2 are capable of pretty significant gains with an im/intake/header/exhaust and AEM EMS or K-Pro with a corresponding tune (<-Critical), that's simply not what you have right now. I'm going to get even more harsh, brace yourself, I'm just giving honest advice; you're not using great parts. A really good header to get big gains is going to be $1000 or more; skunk2 produces decent IMs but nothing special and the stock throttle body is still a major choke point; the exhaust speaks for itself, the diameter is one thing, but the quality of the way it's run does make a difference; the stock ecu, well it can only adjust itself so much in correspondence to the increased airflow. Going N/A is expensive, but a k is a very special engine. With 4 cylinders you can hit about 282whp N/A on the average dyno without going totally crazy and spending tons of money, the good head is pretty much a necessity though and the exta .4L of displacement helps a lot if you have it. Are you registered on K20a.org? If not, do it and research, research, research. Best of luck with the project, please post a build thread and keep us posted.

BTW; I deleted the street racing/thread hijack, if the member who originated that digression does so again in this thread a ban will result.