Will a stock manifold/downpipe/cat benefit from a hi-quality cat-back system?

[H.M.]

Say I have a stock EX with all exhaust components in good condition including a brand new, but stock cat.

Will my car benefit from a high quality cat-back bolt on exhaust system? For example, an APEX-i WS2, or any other cat-back you think is hot.

Wouldn't the restrictions in the small cat be a choke point that would prevent everything behind it from flowing at its optimal capacity? Would I need to replace the cat, flex and/or down pipe to get optimal flow? And then is the header too small?

Or is there an incremental improvement in the larger cat-back pipes and muffler that makes them beneficial?

[stretch JDM]

you will improve sound, thats about it bro. good luck on your build.

[H.M.]

Seriously?

So I have to replace every component of my exhaust system for an increase in performance? Because the upstream components bottleneck the better quality cat-back components?

I'm limited, being in California, to which cats I can install.

[cb7rush]

you will gain sound and about 1hp without a tune..im in cali too so your best bet is to get a carb legal header and a low sounding exhaust or else cops are going to mess with you constantly..

also, your stock cat will work fine with a cat back exhaust system..only thing is that it does stop the free flowing exhaust from exiting better, therefore you are losing power there. but you can take your chance and run an aftermarket high flow cat, non carb headers, and a loud ass exhaust if you want

[H.M.]

Wait, no, I don't want a loud-ass exhaust!

I'd prefer a completely silent exhaust, I have no desire to listen to noise and I don't want anyone to hear me coming. And I don't care about looks. All I want is better performance.

The best I can expect from a cat-back is 1-3 hp?

For better performance:
My existing stock in ok condition (at $0) vs. a cat-back (at $300 or up)

I should just stick with stock?

[cb7rush]

you can benefit from a cat back exhaust if you get a tune. your best bet is to stay stock if you dont want a loud exhaust. or get an APexi WS2 exhaust and call it a day. for you to gain serious hp youre going to have to upgrade your headers, DP, and exhaust. and possibly get a good high flowing cat that is also carb legal (which I think there is a couple of them legal for use in CA, but dont quote me on that)

apart from just getting all that, you would only gain a little hp without a proper tune. It is best if you do not want a loud exhaust and dont want to buy other stuff to just stick to stock.

[H.M.]

What's the benefit of the APexi WS2 exhaust without the cat, downpipe and header? It just gives you as much free flow as possible without increasing noise for $400 or so?

I appreciate the input. So far, you're saving me $$$ cuz I'm now leaning toward sticking with stock.

[H.M.]

So I'm kinda bumping this cuz I'm still wondering if this is correct:

Most of the high end, heavily chromed, 4" diameter bazookas are really there just for looks and to make the car sound loud?

I'm really only going to get 1 hp from a new muffler, even a pricey one?

[cb7rush]

the reason an apexi is good is because you get an aftermarket exhaust that isnt loud as shit and gives you that clean sound you want without it being over the top. It is pricey though.

like I said before, you wont benefit as much as you would if you got a complete H/DP/E and a good tune.

[H.M.]

I'm not giving up on this.

Is there anyone who's bought a cat-back who can prove it's helped performance.

Bueller? Anyone at all.

cb7Rush, it's not that I distrust you, it's just that I can't believe everyone spends so much money on these things and all they get for their money is chrome and a tone they like.

Anyone?

[19dabeast85]

Yes people do. People pay tons of money for looks and sound and imaginary performance every day.

The fact is our stock blocks are designed to have maximum torque and horsepower in the mid-range rpms (3k-5k). The flow capacity to support this is relatively low and so the stock exhaust manifolds and cat are a small diameter to retain adequate flow velocity at these lower rpms to promote efficiency at the engine's peak power.

Installing an aftermarket cat-back will allow better flow, but you're still severely limited by the oem manifold, cat, and cams. As said before, expect a few hp max at the wheels. Your EX already has a slightly better flowing exhaust system than the rest of us so keep that in mind. You won't realize any significant gains from an aftermarket exhaust unless you at least have an h23 IM and true 3" cold air intake. Those together with a catback will net you ~6-8 hp at the wheels. Get a cam along with exhaust and you're looking at +20 minimal with a tune. $$$

[H.M.]

This thread has made me very sad.

But I think it's saved me about $400.

Thanks!