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Howdy all. I just totaled a 03 Accord V6/6MT and picked up an 06 Si last weekend.
I've had a few 'tuner' cars and do all my own mods so I'm really enjoying the DIY nature of this site.
I've been trolling around the past few days and it seems that the best way to get 15-20 whp easily is with intake and a race header. I live in TX and have failed emissions before, and Im not wanting to go thru that again so I want to know if you can still pass if you have an aftermarket header.
I know it eliminates the cat but usually there's another one downstream that will keep you clean enough to pass. Is that the case or would I need to install a cat after the header ( I have one laying around I could use).

So, how many cat's do I have? 1 or 2?
Is 200whp a realistic estimate with these mods?
 

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1 Cat, and you'll probably be about 200 WHP depending on the intake you choose (Hint: Xfactor intake). You'll need to get the vibrant RH as it is the only one available with a cat.
 

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Stock we have 1 cat. Headers will not take place of cat, only a race header will do that. Get a set of good Shorty headers, a downpipe, and catback exhaust, along with an intake. That'll put you around 200whp.
 

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Stock we have 1 cat. Headers will not take place of cat, only a race header will do that. Get a set of good Shorty headers, a downpipe, and catback exhaust, along with an intake. That'll put you around 200whp.
Yes, we have one cat, no we do not have headers, we have A header.

A shorty header will not produce much more power at all, and there is no down pipe available for the Si, just the R18 or EX models.

Your options if you want to run a cat are, buy a High Flow Cat, buy the Vibrant Race header with a High Flow cat (which still isn't guaranteed to pass emissions), or just run your stock cat.

The 200whp mark is realistic with the right exhaust and intake.
 

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Yes, we have one cat, no we do not have headers, we have A header.

A shorty header will not produce much more power at all, and there is no down pipe available for the Si, just the R18 or EX models.

Your options if you want to run a cat are, buy a High Flow Cat, buy the Vibrant Race header with a High Flow cat (which still isn't guaranteed to pass emissions), or just run your stock cat.

The 200whp mark is realistic with the right exhaust and intake.
Easy, easy. :box: Header or Headers, it's the same thing. As for a downpipe, one can be custom made at a nearby shop. Yes a raceheader with cat could work better, but either way, it's just about the same.
 

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Easy, easy. :box: Header or Headers, it's the same thing. As for a downpipe, one can be custom made at a nearby shop. Yes a raceheader with cat could work better, but either way, it's just about the same.
Not trying to start something its just I always see people say headers, and well, we don't own a 6 or 8 cylinder car with headers, we have a 4 cylinder with a header.

And as far as a downpipe, once again there is absolutely no need for one on a Si.

The only reason there is a downpipe made for R18's and LX/EX model Civics is because the downpipe picks up where the R18 cat-backs leave off. For some odd reason, the R18 cat-backs (as far as I know) only include the axle-back and mid-pipe; these downpipes complete the cat-back exhaust by replacing the stock A-pipe that's right after the cat.

If you were to buy a catback exhaust for the Si it is literally from the catback, no downpipe necessary.
 

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x's intake and the vibrant race header (has an available cat) will give u about 200whp. Y not throw a dot approved exhaust on it and get a couple more ponies out of it?
 
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