[brainycheddar]

Hello, I'm trying to comparisons of different cat back systems, but it's really hard to find solid numbers on this sort of stuff. I've got a 15% pulley and a CAI, and a cat-back is next on my list. all the comparisons that I see compare certain exhausts qualitatively to the stock system, which is in general more power and better/louder sound. I'm looking for real HP/torque gains. also, what part of the RPM band are these gains made (no sense in getting 10 more hp @7001rpm if you can get 5ft/lb@3500). Since I'm located in sunny California, it needs to emit less than 93dB @ WOT. also, I'd like it to not sound to ricer/chav-ish.

Main options that I'm leaning towards are the:
borla street
borla sport
Milltek
one-ball
MiniMania

If anybody knows numbers of any of these, that would be great. thanks!

[batou]

What about JCW or JCM?

I went from 167.4 whp to 199.3 whp (increases at same RPM all the way up) from adding the following...

* JCW 380cc Injectors
* JCW GP Intercooler
* JCW Cat-back (without flat section)
* JCM Air intake

Noise wise...
* Quieter than stock when cruising
* Massive raspy roaring sound under WOT
* Loads more pops, bangs and Crackles
* No "chavy" drone or too deep
* Clean sporty note accelerating from low down

I'm also going to go for a Janspeed Header/Manifold, apparently with some cat-backs adding the header/manifold pushes it over the noise threshold whereas you can get away with it on the JCW

My only gripe is it sounds much, much better from the outside than it does from the cabin.

[sef]

I've got the Borla Sport and it added about 1bhp.

My car with a 15% pulley and the Borla made 214bhp. (Flywheel)

The Borla is louder than standard but has a nice deep tone to it... Have a search on Youtube for examples.

I'm having a Janspeed Mani fitted shortly and apparently it does make it a lot louder so If you are looking at getting a new manifold at some point, the Borla Sport may not be for you...

[batou]

Paul @1320 has a Borla on their shop car atm, not sure which one (street/sport) sounds very raspy and aggressive (awesome sound) but very loud. Has a Janspeed header/manifold fitted and standard cylinder head iirc.

[minioneandrew]

Roland from GTT, did a test ages ago comparing the backpressures of catbacks, if you do a search you should find it. I think the Milltek came out with the least back pressure.
regards Drew

[Loui]

Quote: Originally Posted by batou (original)

Paul @1320 has a Borla on their shop car atm, not sure which one (street/sport) sounds very raspy and aggressive (awesome sound) but very loud. Has a Janspeed header/manifold fitted and standard cylinder head iirc.

Thats a cooper borla.

To get past the 93d think your going to have a small choice really. Im running a borla street, dont know about gains but know it works as 239whp an 272bhp runs thorugh it fine, i also think that would pass the noise levels you need to

[batou]

Quote: Originally Posted by Loui (original)

Thats a cooper borla.

To get past the 93d think your going to have a small choice really. Im running a borla street, dont know about gains but know it works as 239whp an 272bhp runs thorugh it fine, i also think that would pass the noise levels you need to

You have the massive exhaust ports on the RMW head and a performance manifold though right?

[Loui]

Quote: Originally Posted by batou (original)

You have the massive exhaust ports on the RMW head and a performance manifold though right?

Indeed

[brainycheddar]

I contacted Borla about their systems, and they don't even know what the dB levels are. They just specify a 5-7% increase in HP and torque throughout the rpm band with either system.

I've yet to contact other ehaust providers, however I'll post my finding for everyone to read.

(edit)

Using a base horsepower model of 163 hp for comparison sake:

-5-7% improvement is an aditional 8-11 advertised HP for the borla systems

-the Magnaflow dyno chart displays an improvement of 13 advertised HP
dyno- http://www.magnaflow.com/02product/dynos/15742.jpg

[hedgetrimmer]

I doubt you will get any tangible increases from a cat back system. I would imagine you are only looking at 1-3bhp max at top end and very little in it further down. The noise will simply make you feel that you are going quicker.

[Loui]

Quote: Originally Posted by hedgetrimmer (original)

I doubt you will get any tangible increases from a cat back system. I would imagine you are only looking at 1-3bhp max at top end and very little in it further down. The noise will simply make you feel that you are going quicker.

What he said

[brainycheddar]

Really? I'm trying to eventually break 200whp. I figured that after a CAI and a 15% pulley, the next logical step would be the exhaust. I've got a scangauge coming, so I'll soon be able to make some estimates. I just thought that after pushing the SC farther the next thing would be to uncork the exhaust. for the same money, what would be a better route?

[sef]

It's the manifold that releases more power... As above my Borla catback gave me an extra 1bhp...

I'd suggest getting a reduced pulley, larger Intercooler and a new manifold to help you on your way to the 200whp figure

[brainycheddar]

...California law says that I need to have OEM smog equipment which means a stock header through a stock catalytic converter, but after cat is free... kinda. the is the quote that I found:

This procedure specifies a limit of 95 dB measured 20 inches from the exhaust pipe outlet with the engine operating in neutral, typically at speed of 3000-5000 rpm.

but if I can save $800-$1100 and not get 1 hp, maybe I should invest elsewhere.