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2 1/2" or 3" exhaust?

E

ExLimey

New member
I'm going to be replacing my exhaust from the down pipe back thanks to a rusted muffler and the previous owner replacing the resonator with a glass pack. It sounds awful and the welding is terrible. Overkill recommends 3" but I'm not making a race car, just a fun daily driver. Is the 3" worth the additional cost or is 2 1/2" good? I'm gong stainless. The only other mods besides what are in my signature are an XP cam, smaller pulley and possibly a set of ported heads. Thanks!
 


Haha, I was just gona edit my first post and ask about a sound difference. What mufflers are you gonna use?
 


Waste of money.

Stock catback supports 350~WHP...you might be close to a hundred less than that.

Just change the mufflers and tips.

Stock resonator is super quiet. If you want a little more noise swap that out for a glasspack.
 


The whole notion that the 'stock catback supports "X" power' is silly.
You'll always make more power with a better exhaust. I say go 3" to 2.5" duals.
It's easy enough to build an exhaust that'll still be quiet and flow well.

I've had plenty of stock catback sub 300whp s/c cars pick up 15-20whp with a cutout on the dyno.
One of the turbo guys made 290whp on like 9psi, opened the cutout and made 330whp, and that was with an SLP exhaust which is bigger than stock.
 
It's been done. Just lots of work and you'll love beating on the firewall.

SnowFlake said:
The whole notion that the 'stock catback supports "X" power' is silly.
You'll always make more power with a better exhaust. I say go 3" to 2.5" duals.
It's easy enough to build an exhaust that'll still be quiet and flow well.

I've had plenty of stock catback sub 300whp s/c cars pick up 15-20whp with a cutout on the dyno.
One of the turbo guys made 290whp on like 9psi, opened the cutout and made 330whp, and that was with an SLP exhaust which is bigger than stock.
Click to expand...

lol, because cutout.

You say make more power and then suggest a bottleneck setup. That's logical. But I can't fight your experience and dyno proof.
 


It's science, bro. Don't you know?

You should give me tons of numbers to show me where I'm wrong and how a catback really gains tons of power on a car that doesn't really warrant the extra flow.

If the OP has an XP/Ported heads/N* and "X" pulley...would it even get close to 325/350WHP on pump gas? Maybe. The debate is that spending the extra $700~ on a ZZP catback isn't worth it when the money can be used elsewhere since a factory 2.25" catback flows just fine. He's already addressed the issue and that's getting rid of the manifolds/downpipe.

I'd like to see the same car side by side gain SAE corrected 10+WHP with just a catback swap that doesn't have a collapsed resonator/muffler on it already.

Go ahead and get on that and let me know how that works for you.
 
In true blueguy fashion you have no actual argument.
The area of dual 2.5" pipes is that of a 3.5" single pipe… tell me where the bottleneck would lie… unless you're saying the single 3" pipe is the bottleneck...
 
I'm still trying to see how your original post has any merit.

But again, if you've got the dyno stuff to prove it, then your post is no more factual than mine is.

My post saying the stock catback flows good enough to 350WHP~ or so has as much backing as you saying a catback adds power.

Plenty of people that have been in the game long enough have witnessed cars not gaining anything other than noise with an aftermarket catback.
 
Hmmm… a bunch of anecdotal nonsense or black and white dyno numbers.
I wonder which has more 'merit'.

You still haven't told me where the bottleneck is on a 3" to dual 2.5" exhaust.
 
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