I gave up trying for a baseline time of my stock HHR, and finally put in the IMCO muffler (already have the CGS on). But natually I had to be different. I put a Y pipe before the muffler, and ran it to a header collector, creating a true 'lake pipe'. By putting a solid plate between the collector and the exhaust tip, all the exhaust goes through the muffler. Remove the plate and I have open exhaust. Add a plate with a few holes in it, and I have a semi-open system. Here are some pic's.

http://www.chevyhhr.net/gallery/files/3/2/4/backviewDSCN4459.jpg

http://www.chevyhhr.net/gallery/files/3/2/4/EntireDSCN4444_476032.jpg

http://www.chevyhhr.net/gallery/files/3/2/4/RightunderDSCN4446_487397.jpg

http://www.chevyhhr.net/gallery/files/3/2/4/LeftunderDSCN4445.jpg

Great set of picture! I'd like to know how that sounds!

I dont know yet. From the car it is not very loud totally open. But, I thought that the IMCO was too quiet. I have to get my son to video my driving around the block, then I will post it.

I'm kinda simple so let me break this down to see if I understand.

full plate-single exhuast
open plate-dual exhuast
holes in plate-dual but with more to mufflerIs that it?

Are there any concerns about heat from the pipe routed to the passenger side?

Thats the story. The way the y pipe is, it only relieves the back pressure going into the muffler. It is actually a t, not a y. So not a lot of heat goes to the second pipe. But, it about a foot from the fuel emissons box behind the rear, and several inches below the spare tire well so I do not think that heat will be any problem. If so, I can always add a shield. But exhaust pipes run under the car without any heat issues.

Thats the story. The way the y pipe is, it only relieves the back pressure going into the muffler. It is actually a t, not a y. So not a lot of heat goes to the second pipe. But, it about a foot from the fuel emissons box behind the rear, and several inches below the spare tire well so I do not think that heat will be any problem. If so, I can always add a shield. But exhaust pipes run under the car without any heat issues.

I'm just thinking about my next mod.

Since we put the lakes on Bonnie's, I'm thinking of hiding her tailpipe so its not so obvious that the lakes are fake (I know they will all be capped, but most people may not even notice). so I'm thinking of a way of using her factory tip on my to give the appearance of dual exhaust. Would be even cooler if it really was!

What about back pressure? I thought that the HHR needed enough to run well. Wouldn't opening it lessen that and mean less performance? (I'm not bashing, just asking cause I don't know.)

That is an excellent question. I will have to test it both ways at the track to see (or with my GTech). But I am sure that the IMCO is not at the exact correct back pressure, so there will be some variance. And by using the right amount of holes in the blocking plate, if I could get it on a dyno, I would be able to find the sweet spot.

For now, it just sounds more aggressive. Plus, it has dual exhausts that are not phoney like the fake tail pipe someone sells on the internet. If anyone looks under the car, they will see it is connected!

I'm really loving what you've done and I'm thinking that this may be the way to go.

Keep the info coming, thanks.:thumb:

Excellent work Lee!:thumb:
You seem to know what it will take to get the best performance out of that system with the variable plate aperturs. Do you have a lift or are you jacking and grunting everytime you go beneath the HHR?

Looks good Lee :thumb: Keep us posted on how it all works out

thats how my borla exhaust on my trans am was, i always ran it wide open ;)

I really love it. I was at a car show yesterday and there was a salesman from the Chevy dealership where I got my car. He noticed the exhaust and loved it. Was also impressed with the intake.

I need to bring the car in to check on brake chatter. I will see if the mechanics notice.

Looks good LEE - nothing new there. Just wanted to add thought to your dual exhaust by stating there ARE "Y" pipes (not sure about "T's") on the market that have an ELECTRONIC solenoid that actuates the blockoff plate!!! Talk about trick:eek:!!! Flick a switch and your runnin' straight through's? Flick it back and it's back to stealth? :thumb:
Nice work... just some food for thought. Can't tell by the pic's if the 'T' that's in there now is bolted, or welded, in place.

It is welded. I checked the electronic ones, and they are expensive. Plus, the collector and block off plates are easy to reach. And, with my system, and can have partial open exhaust.

Looks sweet Lee. Should sound something like my functional sidepipes when you have it opened up. You'll notice a difference when you go from the muffler to just open free exhaust.
Good Job!!!!!!!!!!!!

Looks sweet Lee. Should sound something like my functional sidepipes when you have it opened up. You'll notice a difference when you go from the muffler to just open free exhaust.
Good Job!!!!!!!!!!!!

Aside from the noise what do you mean by "you'll notice the difference?"

i also have dual exhuast and it pulls harder and accelerates a lot better. waiting on the underdrive pulley in the mail, then intake next stop tune see you in the high 13's after that.

Aside from the noise what do you mean by "you'll notice the difference?"

The car will pull harder and have more torque. Mine also gets better fuel milage.

Mike, Howdy-where are you? What do you think-yay or nay?

I love it. :thumb: Awesome job Lee! :bow:

Captain-thanks, buddy. I was wondering where you were:confused:

Now if I could just get Mikes seal of approval...

I am going to post some video/sound clips of the car with the stock exhaust, the IMCO closed, and the IMCO open.