Big Kahuna

I am running with a stainless steel Magnaflow w/o catback on my 2.4 2LT HHR... Also have the CGS intake setup under the hood.

LOVE the low mellow rumble...
Lot's of compliments...
Excellent performance!

Definitely NOT a fart pipe ricer sound...

1Panel2NV

gmpp exhaust on a 2.2
http://s134.photobucket.com/albums/q...nt=exhaust.flv

Magnaflow catback
http://www.youtube.com/watch?v=DgXruXzvrZ8

Several videos of 2.4's
http://www.cobaltss.net/forums/showt...exhaust+thread

xzombiex66

on that GMPP 2.2 it sounds like they took off the resonator here's my GMPP with the resonator on, its a lot louder now that its broken in. I did this video the first day i put it on. I have been thinking about removing the resonator to see how it sounds. Also the camera i used blows it not a good camera at all

http://www.youtube.com/watch?v=zrpZuhv6rhw

kwboydston

Just installed my Magnaflow cat back 2 days back, so far I like the tone but wife thinks its a bit loud.

The Curly 1

I will be doing a complete exhaust system on my 2.2. I have ordered a complete 2.4 exhuast including downpipe, cat, resonator it is larger than the 2.2 system. We will be doing some side by side tests to verify performance gains (or losses) before and after. I am also taking mileage records on this car as I make changes. This system does not have a muffler and I will test it some with out a muffler for a while to see how it does and if in fact it really does need backpressure. Then if it performs much better I will put a large free flowing muffler on it to try to quieten it back down.
I suspect it will run much better and get better mileage with new system but I am testing so what ever happens I will post it so everyone learns. I also believe (hope!) it will improve more once I do the Trifecta tune to correct the fuel mixtures and timing curves for the better breathing.
So in answer to the original thread what is the best muffler for the 2.2?
I do not know yet but I am working on it.
There are 2 very different opinions here.
1. GM is perfect and the factory system can not be improved on.
2. My opinion that the cars are built to be very quiet for the general public and that hurts performance and mileage some. I believe that opening it up some will help performance and mileage (as long as you drive the same)
When it is all done I may do a 200 or so mile test run and then put original intake, exhaust and wheels and tires on there and make the same run at the same speed to verify results. Also make a few runs against the same car to verify performance. It may take a few months but I will be able to give you some answers.

halfpanel08

so much testing curly.. but im ready to run wen u r

and how much is the gmpp exhaust?

stelerz

I have the Imco and it sounds like the magnaflow to me.I don't think it sounds, ricey as you put it.

The Curly 1

I am not getting the GMPP cat back exhaust. I bought a complete standard 2.4 exhaust which is about .5 larger than the 2.2 and has a larger cat.
It is larger from the manifold all the way back not just from the cat back. Now if it works as I think it will I may go even larger from the cat back later.

HHR Nole

I had a Magnaflow with 2.25 inlet and outlet put on the stock pipe. The muffler shop was able to weld it on with an adapter and use my stock hangers off the stock muffler,also had a bolt on tip that I already had. With the K&N air filter in the stock box and with the muffler after resetting my ECM it made a real differrance. Car has much better pickup and mileage plus it has a nice sound,not a ricey one.

IgottaWoody

I'm with Curly..anything the factory makes stock CAN be made better,especially exhaust.The exhaust is restrictive and too quiet..thank you very much EPA and noise level mandates( and design limitations).The intakes are designed to minimize noise therefore some restriction..theres too many sensors in the intake path creating turbulance and restrictions.....
it always amazed me how the weekend rodder can make some small inexpensive changes and increase power AND milage AND cleaner exhaust but yet the factory types cannot..and these changes would not have any adverse effects on anything,peroid.Even a simple thing like cam timing...maybe because they can't put a stamp on it and overcharge. I think they like to limit the improvements so they have something to sell next year.