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Discussion Starter #1
Ok, so I need some opinions here on what to do. I have an 04 D23 with the Fswerks 2.5" race exhaust and K&N Typhoon CAI with no tune. I have two options on what I can do next because i'm on a very tight budget. My first option is getting an aftermarket header and flex but the problem is that I'll need to run a high flow cat (dont ask) and this will be with a tune. My second option is getting some stage 1 cams with a tune. Now i have two questions, would the cams and tune not be worth it with the stock exhaust manifold? and how much of a loose am I going to see with using a high flow cat vs going catless?
 

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I would go with the first option, but would save some more money and do something nice, I understand it is a bit expensive but what i've read is: it matters how fast you could get the air and fuel in, but it also matters how fast you can get it out and I think that if your exhaust system can't stand it those cams you want to put in I think will be more or less waste of money. And if you want to go catless (assuming - no catalytic converter) then you will not pass emision test, unless you create some type of bypass valve in exhaust system, to have it only for the test.

That is just my opinion, but I may be wrong.
 

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Discussion Starter #3
Yeah, I understand that but I can't run catless. If I get an aftermarket header, I would need a high flow cat welded in somewhere. I also know the cat is the choke point on any exhaust so idk if going with a high flow cat is even worth it or not.
 

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slow
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Yeah, I understand that but I can't run catless. If I get an aftermarket header, I would need a high flow cat welded in somewhere. I also know the cat is the choke point on any exhaust so idk if going with a high flow cat is even worth it or not.
High flow cats are becoming much better at flowing then they used to be, and if you can get away with it, adding a cat after the flex pipe may be an option. You won't get quick response of the Cat at start up, but it'll work once it gets up to temperature.

The manifold-cat setup on the PZEV D23s is very restrictive, and a universal HFC further back in the exhaust system will be a good improvement IMO.
 

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Discussion Starter #5
Yeah, I think what I'm going to do is just get the header and new flex and have a shop weld in a hfc somehwere in the straight pipe. I was looking at davesport hfc's and they seem pretty nice; metal subtrate with only 100 cells per inch. That's the lowest i've seen so I think i'm going to go with that. Any opinions on other hfc's out there??
 

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w/ my magic bag
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For a great header, Focussport= Header & flex-pipe. If going w/ a converter, Magnaflow make's one that bolt's right up to your flex pipe. Check out CFM's site= Central Florida Motorsports!
 

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Discussion Starter #7
The fswerks header is very nice but I like the sound of the OBX header with the Fswerks race exhaust. I think that's what I'm going to do, buy the OBX header with a davesport high flow cat and call it a day as far as the exhaust goes
 

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Noisey exhaust= no good!

The fswerks header is very nice but I like the sound of the OBX header with the Fswerks race exhaust. I think that's what I'm going to do, buy the OBX header with a davesport high flow cat and call it a day as far as the exhaust goes
Do you know how LOUD a Header w/ a race exhaust is, any idea? It sound's awesome for a quick drive around the block, then you regain your sense's & say I have to quiet this racket down, for a DD. I've had quite a few loud V/8 car's, & had to queit them down. You'd be surprised how much faster you can go, instead of the noisey exhaust dictate how fast you go. Try 2 stealth muffler's after the flex. Or try a couple of 18-20'' magnaflow's.
 

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Discussion Starter #10
Trust me, I know how loud it can be. I've driven in (and I'm not bashing them) hondas with headers and aftermarket exhaust so I know how loud a 4-banger can get but again, I've heard the exhaust note of an OBX header and an fswerks race exhaust and although it may be loud, I didn't find it annoying. Plus too, the hfc will quiet it down just a tad so i'm not worried about it. I like sound but my main concern is performance.
 

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br/o/stang
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[thumb] OBX ftw
 

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The HFC will quieten down alot from what I hear. X2 on the obx header.
 

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Do you know how LOUD a Header w/ a race exhaust is, any idea? It sound's awesome for a quick drive around the block, then you regain your sense's & say I have to quiet this racket down, for a DD. I've had quite a few loud V/8 car's, & had to queit them down. You'd be surprised how much faster you can go, instead of the noisey exhaust dictate how fast you go. Try 2 stealth muffler's after the flex. Or try a couple of 18-20'' magnaflow's.
I know how loud it is :) I love it!
 

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Discussion Starter #14
The HFC will quieten down alot from what I hear. X2 on the obx header.
bespurcell, i dont know if you'd know this off hand but how much would the hfc actually quiet down the exhaust? The davesport hfc is just about the highest flowing cat I could find. Also, does anyone know how it will effect horsepower numbers from the header? Basically, how much will I be robbed of? lol
 

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bespurcell, i dont know if you'd know this off hand but how much would the hfc actually quiet down the exhaust? The davesport hfc is just about the highest flowing cat I could find. Also, does anyone know how it will effect horsepower numbers from the header? Basically, how much will I be robbed of? lol
It will still be plenty loud. I have 3 mufflers and it's still loud. Not sure on the cat hp robbing as I don't have one.
 

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Busy Monkey
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I can't tell by this thread whether or not you know this, but you have 2 cats in your system. One in the exhaust manifold and one after the flex pipe. So if you install a race header you will eliminate one but you'll still have one cat below the header and flex pipe which can be replaced with an ORP, a resonator, or a HFC
 

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Discussion Starter #17
MisterJohnson,
I'm aware that there are two cats.. or were two cats for that matter. I already had the secondary cat removed because of the Fswerks Race exhaust I have installed. My question still stands though, what would the horsepower difference be between a catless exhaust with header and the exhaust plan i have that includes, an OBX header, davesport HFC and fswerks race exhaust?
 

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Busy Monkey
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If you don't have emissions testing then I say go catless and see if you like the sound. HFC's do flow better than stock, but they're still restrictive compared to a straight pipe
 

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I can't tell by this thread whether or not you know this, but you have 2 cats in your system. One in the exhaust manifold and one after the flex pipe. So if you install a race header you will eliminate one but you'll still have one cat below the header and flex pipe which can be replaced with an ORP, a resonator, or a HFC
only on pzez models(= finally got this clarified from ford. non pzez have only the one manicat
 

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MisterJohnson,
I'm aware that there are two cats.. or were two cats for that matter. I already had the secondary cat removed because of the Fswerks Race exhaust I have installed. My question still stands though, what would the horsepower difference be between a catless exhaust with header and the exhaust plan i have that includes, an OBX header, davesport HFC and fswerks race exhaust?
there will be a hp difference but probably not anything too drastic. based off my hours of studying this forum among others id say at least 2hp would be lost due to the cat. The truth is cats are stupid and the only thing they do is "catalyze" some of the harmful gases being released by an automobile and in the process causing the whole exhaust system to be restricted. have you ever seen the inside of a cat? its not just a honeycomb causing restriction like people say. sure a hfc is better but its still a cat. just put in another resonator to make it more quiet. resonators do NOT rob any performance because they are flow through in design without restriction. they just have holes in them just like the silencer on a pistol would cause the air to be dispersed with less sound.

header, flexpipe, 30" resonator, 18" resonator, and a flowmaster muffler at the back. thats my exhaust. i would even suggest a flowthrough style muffler at the back instead of a chambered because even then there could be a gain of 1 or 2 hp. i just love the deep awesome sound it now has so i cant change it lol.
And before everyone starts bashing saying "its only 1 or 2 Hp" think about it for a second. if you do 5 tweaks that free up 2 hp thats a 10 hp minimal increase. on a car that was originally putting out 120hp or so? thats a gain of 12%!!!!!! (=
 
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