Some background info:
This is a 2.5" catback which I mated up to the Hahn 3" catted DP. No, it's not a 3" Catback.
I went with this one since it was dyno tuned for sound and power. Agency claims 10 HP...I can't verify this. The rationale behind this is that the exhaust loses heat and contracts as it moves back, so you *may* not require as large a pipe. It's the DP that really needs opening up, not the catback. What you want is to maximize velosity down the pipe and if it's too large for the volume of gas, you will lose power and torque. Still many say a 3" better ...I can't say for sure, but 2.5" will support 300WHP easily...IN THE CATBACK, so a 3" cataback shouldn't provide much more (if any) power than the 2.5". So, why not 3" then?
It's LOUDER and heavier for sure and probably would cost a more torque in the LOWER end. Why then, not leave the stock 2.5" in place? The answer is that you can still maximize flow and velosity by using smoother bends and straiter pipes going into a performance muffler. Look at the pipe going into the stock muffler vs the Agency. Also the SOUND on this set up is simply amazing! . No rasp or drone, just a deep mellow growl. I'll try to get a sound clip and post it here.

Here are some pics:

Stock vs Agency Muffler and pipes:





Stock rear shot:



Same shot Agency:



Another rear stock shot:



Same shot Agency:


Front to back shot stock:



Same shot Agency:


Stock muffler on car:



Agency Muffler on car:


BTW..Notice 3" MxP Muffler pipe has a *dog leg* bend, not straight out:



MxP hanger is on the LEFT side..diverting the pipe to the right before the axel. Why did they do this? To accomodate the larger diameter pipe?


Agency Pipe is STRAIGHT OUT:








Before:

After:

 

me want sound clip!!!!!!!!!!!!!!!!!

 

hey ronn, is this your christmas present?

 

i see pedders.

Cant imagine it would sound any different than someone with a dp and cut out the stock muffler. I run a catless dp with stock catback, sounds awesome when on it, quiet when im not, no rasp no drone. Tip looks nicer tho...

 

I'm gonna try and get one done.

Mean time I found this one:

https://www.cobaltss.net/forums/part...atback-214941/


$390 out the door and shipped. This was MSRP over $650!

 

wow, good for you man.

 

Here are two sound clips. The I Phone was held very close to the muffler, so the sounds are a bit exaggerated. The first is without the silencer. The second is with it. I modified the silencer. See pics below video.



cobalt_exhaust1.mp4 video by RAHOD_photos - Photobucket

With Silencer
cobalt_exhaust3.mp4 video by RAHOD_photos - Photobucket

Silencer takes a couple min to warm up and the *tin can* sound vanishes to a very quiet mellow sound. You don't get all that in this video. I left it on.

The silencer is modified for more flow. I drilled four holes on the outer plate. It had four on the inner plate only..I also made them larger. Here is a pic of the Megan Silencer..mine is exactly like this one, only with four holes added to the outer plate:



On the car:



Inner plate holes can't be seen on this pic



Car has great sound with this on. It was was a bit too loud for my taste and had some *drone* under load without it.
At WOT (only), there is a *WHISTLE* sound as the air exits from the holes

One more thing...

I noticed throttle response at lower RPMs was more *sluggish* with this set up and when I put the silencer back on (more back pressure), the throttle response (torque) was definitley better. I ran WOT with the silencer off and my *ricer run* from 60-100 was the best ever..6.18 sec. So I assume HP was maixmized with this cataback added to the DP. I'll report the results with the silencer on soon.

Update: 6.3 sec with the silencer on..pretty damn close to without. BTW got a ticket doing this run. See my post under the *60-130* thread

 

Dynoed with DP..Catback and Silencer. Results were almost unchanged....9 less peak HP. Looks like power started to slip around 4500 RPM compared to stock exhaust.
Dyno tuner (Shaun Church) said the small Silencer (1 1/2" outlet) was costing me HP, even though I drilled some holes. I took it out and will redyno within a week and post results. That way I'll have good info on comparing stock...and DP/ Catback with and without silencer.
Here is comparison's so far:

Stock Exhuast:
Note: The lower green line was the original tune the car came with.


DP (Cattted), Agency Catback WITH SILENCER:
Note: Lower green line is the third run when engine was very hot, thus low #s.


STAY TUNED DYNO WITHOUT SILENCER!!

 

the silencer is killing you. lol. and i agree about the whole 2.5" catback vs 3" catback. to be honest, i believe a 2.5" catback will keep the exhaust velocity up compared to a 3"

i have a feeling im going to be losing some power with the exhaust i got for mine reguardless tho. lol. doesnt bother me, it will be minimal at least.

anyway, exhaust looks on point

 

Well, I guess I'll be eating some humble pie soon. That's what this forum is all about...seeking GOOD INFO and sharing it. Can't wait to redyno. I'm really expecting at least a 10HP gain over stock set up. If that's the case...that silencer was costing me almost 20 HP. We'll soon see.

 

lol. im probably going to get it once i install this on my ss/tc....



but who cares, its diffrent and im doing it cuz i want to.


and 20whp on the silencer... thatd be crazy. lol. but i wont lie even with the drilled holes that thing looks like its seriously blocking a LOT of flow. even if you barely gain any power without the silencer, its still a nice piece. i likeee, who cares if anyone else thinks its dumb.

 

im hopefully installing my agency power tmrw, ill probably be the only ss/sc with one

 

DUALS?? Very nice.

Tuner wanted to take it off right then and there! Told him it was a pain in the A$$ to remove and that I was gonna keep in on anyway. Said the outlet was..TINY.
Now it's gonna stay off, since sound isn't bad at all...just a very mild drone under load. No rasp at all. I actaully had another silencer which was about 1/2" larger in tube diameter, but it's too FU$$KN tight..2mm larger.

 

lol. i hate silencers. no point in buying the exhaust if your going to use a silencer all the time.

i just realized i gotta do a little work on the slp exhaust i have. gotta make the end that bolts up to the downpipe 3" and then have it taper down to the regular 2.5" size. this is going to be a fun install....

 

that silencer needs to go lol

 

Well either way it goes Ron ........ You are providing valuable information for the community..... thank you . I hope people appreciate it .

On the other hand ... I would give up a little bit of hp for a perfect sounding exhaust ..... but i would really have to love the sound 8)

 

In for sound clips...

 

Already posted above...with and W/O silencer.
Here is without again:

cobalt_exhaust1.mp4 video by RAHOD_photos - Photobucket

 

let's throw on my k&n sri and see if theres a power increase

I never got to dyno and see if there was a difference

 

Church Automotive is in Wilmington and only charges $80 for three pulls.
Go for it.

 

no on your car mine doesn't exist anymore LOL

I still have it laying around thats why I said it

 

Why didn't ya sell it?

 

It is for sale just nobody bought it yet it's up for $150

 

Not bad..

I was thinking of adding the ZZP INTAKE tube..retaining the stock air box instead. It was on sale today and I missed it. Anyway, this is what I may do down the road.
Pic:

 

yea it was half off!

anyways this is going to be one of the best dollar to dollar buys out there you should get some nice gains with it for the price.


do you have a sound clip?