I have searched and asked people in person and can't get a straight answer. My question is what are the disadvantages of a catback exhaust? I plan on getting the GReddy EVO II catback and know it will flow better than the stock and sound better as well, butnothing in life is free sowhat are some negatives. Will I lose power anywhere or will a spot in the power curve flatten out? If anybody has any firsthand experience with just a catback please share. People with full exhaust only reply if you you did the header and cat at a different time than the catback.

 

you will only lose a noticeable amount of power if you get an abnormally large piping: eg. 3.5" on a N/A car. additionally, what loss you might feel from a piping slightly too large won't be enormous. you won't be losing 10HP across the whole powerband. you'll be losing like .5-2HP. the piping that comes stock is usually a good size if you don't plan on any other major mods, such as turbo (IMO).

 

So what about gains as well, as I have read some people expect like 15-20 hp out of a catback, I know better. I was wondering ifthere is noticable gains low, mid, orhigh, or any notable loss or flat spots in the power curve in the low, mid, or high.

 

15 to 20 in larger, high output motors, but on a civic expect about 5 to the wheels for a good system. The Overall peak gain might not be much to brag about but it will even out your entire powerband for a better feel. Once the entire exhaust system from teh header back is upgraded it will be a breathing beast... you'll feel the difference.

 

generally, the bigger the tubing, the higher up in the powerband the gains will be. You'll probably actually see gains of anythign from about3-10 hp... obviously, that's a large window, but nobody can really tell you exactly what to expect; each vehicle reacts differently to modification. I doubt you'll actually get any noticeable flat spots, but it might feel like it. The reason behind this is simple: you'll have gained power in some areas of the powerband and not others. When you're in the rev range where power hasn't drastically changed, it'll feela little sluggish compared to the range where you gained power.

I believe the EvoII exhaust uses fairly large tubing (and by fairly large, I mean around 2.5"), so I'd expect gains in the mid to upper rev range.

 

Thanks guys, right now there are no plans on the table to do a header, maybe a high-flow cat because I have heard that they flow almost as well as straight pipe while keeping it legal. I get enough crap about the mustang not being "environmentally friendly", so I think I'll just stick with the catback for now.

 

why no header? they dont affect emissions at all, and the gains are usually bigger than those of a cat-back.

 

well i had noticable loss in torque with catback, but noticable top-end gains as well. I say go for it, the sound/power is totally worth it, and why no header? Your exhaust system is only as good as its most restrictive component

 

^^^reaper^^^ "why no header? they dont affect emissions at all, and the gains are usually bigger than those of a cat-back."

i heard that putting the header on eliminates the catalytic converter, so how will it not effect emissions? i've been holding off on putting on a header because of this and have been thinking of only getting a high flow cat instead. please explain so i can have a better knowledge of this and possibly throw a header on this week.

thanks in advance. PM me if you could

 

^ if you have cat/exhaust manifold combo, then yes it will eliminate the cat and make you totally fail emissions, but i dont think the 07 SI has that like the 6th gen and 7th gen DX's do, so you should be good.