PulpFriction

Lotsa good stuff! Saw someone who needed to replace a stock SS system. Will try to find him.

Maybe you know the difference between an SS automatic muffler and an SS manual one?

2005HHRauto

Believe it or not GM made 2 mufflers for the SS.
One for the manual & one for the automatic.
The manual one is a little quieter than the automaic one as it has twice to three times as many holes in the 2.75" internal tubing that's appx: 18" long.
The 2.75" internal tubing that is 18" long is awesome!! as the SS muffler will flow as good as any other aftermarket muffler out there, & support all the power that we can throw at it.

Even the SS 2.5" piping is awesome with beautiful bends & free flowing.
While I'm at it, the resonator is 2.5" straight thru free flowing also, & the downpipe is a beautiful 3" with just the 2nd 'cat' choking the flow, & this is an easy 'fix' when 'cored'.

Back to the mufflers LOL
The manual internal tubing looks like most aftermarket straight thru mufflers with rows & rows of holes everywhere.
The automatic internal tubing only has like 6 rows of holes on the bottom & the same on the top.
Absolutely bat **** crazy GM.
If I was a bean counter at GM I would have said NO NO , the manual muffler would be perfectly ok for both automatic & manual SS buggys. LOL

So, back to the total HHR SS exhaust system.
All the you need to do is 'core' the 2nd cat & it will be the best exhaust system for our buggys.
I turned 12.4s will the stock exhaust system with a 'cored' 2nd cat.
I removed it & went to a full 3" exhaust system & picked up just a tenth of a second at the track.
The stock exhaust system rocks!!!

PulpFriction

Wow! $0.50 question, $50.00 answer! Thank you! This deserves it’s own thread!

I know a guy who retired from GM, said he was the “part number nazi” for a certain system in all cars.

Apparently, the designers are prone to create new part numbers for trivial reasons. “No, you’re not getting a new part number because you’d like the lanyard on the gas cap to be 1/2” shorter.”

Pretty sure he would have resisted that SS automatic muffler. Maybe it was needed for air quality or noise compliance. Like the restrictive 2nd cat.

2005HHRauto

Ok me thinks also it was somehow related to the noise compliance, (to be called an SS), BUT, BUT also they really took away a ton of power from the automatics, because the bean counters thought
that guys would be blowing up the automatic trannys causing high warranty costs for the general.

BUT, the bean counters were wrong!! Our 4t45e rocks!! It's very durable.
I've heard that our 4t45e is more durable than the 4t65e.
Transmission shops repair way more blown-up 4t65e than our 4t45e.

Ok, back to the mufflers. LOL
Which came 1st, the chicken or the egg.
So which came 1st, the manual muffler or the automatic muffler. LOL

Since our HHR SS was the 1st SS since the 05-07 Malibu SS disaster, GM wanted the HHR SS to rock.
After all, GM was mocked pretty bad as the whole world thought that the 05-07 Malibu SS sucked as it didn't meet the STANDARDS to have a model called a SS.
GM decided that future SS models, starting with the HHR SS, had to have more power, better handling, better braking, stronger parts, & SOUND better, to be called an SS.

So with that being said I truely believe that they really did design BOTH mufflers at the same time.
The engineers knew that the Manual would need more sound control, & they knew that the automatic would be a 'dog' with all of that power removed to 'save' the tranny. LOL
So, the automatic muffler doesn't muffle the sound as much as the manual muffler.
So, the engineers won the battle over the bean counters because SS. LOL

It was for SS quality......LOL

ps, another $50 answer for you. LOL

PulpFriction

I seem to remember something about the 4T45E in the HHR SS (3.29:1, one of 4 ratios?) having a hardened output shaft or something.

I imaging the pre-LNF Cobalt SS’s were disappointing, too; 2006 in particular, had LE5, same as a HHR 2LT (wheeze.)

The GMPP tune promised 290HP for auto as well as manual. Although rumor has it that that was underrated at least for the manual, I, like you, kinda doubt the the skinnier muffler itself reduced the HP any. I like you theory that it was all about sound. Also, the manual is more likely to pass an occasional backfire, maybe?

2005HHRauto

The 4t45e in our buggys did have some more durable parts, as the general was really concerned about warranty issues.
It really wasn't much, but every little bit of improvement helped, & it was the end of the line for the 4t45e as the the general was dumping them in favor of the 6 speed trannys, for better gas mileage.
Yes there was at least 4 different ratios, & at one point in time I thought of going with the 3.63 ratio to 'push' me into the 11s at the track with slicks.
Mine has held up very well at the track, with many many low 12 second passes with slicks, pushing at least 450 foot pounds of torque thru the 4t45e.
With street tires I have wheel 'spin' thru 1 & 2 gears, & hookup only when going into 3rd, so going to a 3.63 ratio would be ape **** crazy on the street... LOL

I know nothing about the older Cobalt SS & I thought that they were all 'supercharged?

The GMPP 'tune' was rated at 290hp, BUT our PCM is a 100% TORQUE BASED PCM, so ALL changes have everything to do with that wonderful increase in TORQUE... LOL
Everyone should at least have the GMPP 'tune' in their buggy... LOL It is safe & powerful.
The 'engine' part of this 'tune' was the same for both tranny's & the automatic 'tune' had changes to the automatics controller to take advantage of the increased engine performance.
The GMPP 'tune' has built in 'safety' features so that you will have no worries about hurting your engine or turbocharger.
This is the 'base' 'tune' that everyone should use when going to a more aggressive 'tune', because of the new built-in safety features.
If GM had used this GMPP 'tune' as the 'stock' 'tune', everyone would have bought a HHR SS... LOL

Remember, it's SO EASY to HotRod our buggys for increased performance.
1. E47 'tune.
2. 'Core' the 2nd cat,
3. K&N air filter system.
4. Better motor mount.
With slicks you will be in the mid 12s at the track.
On street tires you will be slipping & sliding into the low 13s, as it is so hard to get into the 12s on street tires, but you will be smiling & laughing all the way down the track...LOL

skinnier muffler ??? NO SUCH THING
Both mufflers are exactly the same except for the amount of holes in the internal 2.75" piping.
Our stock muffler is the BEST muffler for our buggy.
Changing out the stock muffler will only increase sound & will have ZERO impact on hp/torque.

For more info checkout this thread:
https://www.chevyhhr.net/forums/hhr-...t-power-43170/

Cored 2nd cat using the 2.75" automatic muffler internal pipe that I had on hand when I took an automatic HHR SS muffler apart... LOL
Notice the 6 rows of holes.
There's another 6 rows of holes on the opposite side of this pipe.



ALL HHR SS mufflers are of a straight thru design with 2.75" internal piping as shown in the picture above.


The worst muffler is the stock HHR LS & LT as shown below with the top removed. What a piece of horse ****!!!!!

hhrumadbruh

Anything that will make a 2008 auto ss sound more like a throaty Subaru?

2005HHRauto

Well that's easy peasy...

Just remove your muffler & replace it with piping & a nice chrome tip.
It's called a "muffler delete".
You can search this forum for threads about "muffler delete".

Because we have a turbo, two cats, & a resonator, the sound will amaze you when you do a "muffler delete".
There is a zero horsepower gain with this modification as the SS muffler is of a "straight-thru' design with zero restriction to exhaust flow.

PulpFriction

With the SS there is absolutely zero performance gain in a muffler delete. Only obnoxious noise gain. HHR SS sounds pretty good from the factory in my opinion.