GMPP exhaust on 2.4?
06-14-2012, 09:11 AM
#14
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Join Date: 10-02-2005
Location: VA
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Behind the resonator, the HHR necks down immediately to 2.25", where the Cobalt necks down to 2.25" in the portion over the twist beam. Just a short length difference there!
The mufflers (both) are 2.25" inlet. Construction is the same and NOT restrictive!
The Cobalt pipe to tip is longer than the HHR due to body differences.
IMHO, not really worth it!
06-14-2012, 02:08 PM
#16
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Join Date: 10-02-2005
Location: VA
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FYI for everyone....
The earlier HHR 2.4 and Cobalt SCs used the exact same manifold. It flows better than most think!
The Cobalt SC downpipe is larger than the HHR 2.4 and necks down just before the catback flange. On HHRs, the downpipe is slightly different for auto and manual trans due to engine "clocking". Never had a chance to compare.
The only dimensional difference in the catback is behind the muffler.
As for the hangers, the front one, at the back of the resonator is the same. The others, I'm not sure of.
As for the muffler itself, years ago, before the SC, I put a straight through Magnaflow on the wagon. At that time I only had my tune. No other changes. Dyno showed absolutely no gain! Which made be take a cut off saw to the "turtle". There's a pic in my gallery. So, if anyone uses words such as "the restrictive stock muffler", get ready for a digital arse whuppin'!!
And, if anyone mentions "back pressure" as being a good thing.... Well, I'll probably get banned.
Exhaust is all about flow and maintaining velocity for cylinder scavenging. Yet some, especially the kidz on CSS.net, seem to think bigger is better!
Currently the fastest street SC Cobalt is a friend that I've tuned for years now (and currently porting his cylinder head) that turned 12.0 @ 117 in the 1/4 mi. His exhaust is a 2-1/4" GMPP catback!BOTTOM LINE: For the 2.4s the stock exhaust is plenty for anything other than a highly modified car. It just works! Anything else is money wasted or just noise!
06-14-2012, 02:12 PM
#17
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Join Date: 10-21-2008
Location: hemet, calif.
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Yeah for the price I'll probably just go with the Imco. I've heard good things about them before and at least a few members here are running them. The magnaflow universals are not really what I'm looking for sound wise and I just can't spend 5 bills on an exhaust...maybe much later down the road.
Last edited by jay loukakis; 06-14-2012 at 02:13 PM. Reason: most members are going with the Imco T-740 about 3 inches longer.
06-14-2012, 02:14 PM
#18
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Join Date: 06-30-2010
Location: Kannapolis NC
Posts: 25,739
The intermediate pipe is located between the flange at the end of the downpipe and the muffler, I thought that there was a length difference between the Cobalt systems and the HHR, maybe its a faulty memory Joe.
06-14-2012, 02:23 PM
#19
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From the flange at the end of the downpipe to the end of the system at the tip, it is all one welded assembly.
Not sure about other Deltas, but I think I recall where some platform other than the Cobalt had a length issue, maybe Saturn. And, before you say faulty memory.....
06-14-2012, 02:26 PM
#20
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