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Custom exhaust system/experiment

18K views 58 replies 10 participants last post by  ZR2LIFE 
#1 ·
Here is what I've come up with so far for a modified exhaust system. There are 2 mufflers on the Trailblazer. The first one which is right behind the catalytic is more of a resonator while the second one under the rear bumper is the main muffler. I decided to remove the rear muffler and put a y-pipe in it's place with 2 exhaust pipes leading up to the dual exhaust tips. I figured the huge rear muffler was very restrictive and just removing it results in very good power gains of at least 10hp and 10ft lbs tq. I honestly believe the gains are much higher, but I'm trying to be realistic at the same time.

Front muffler/resonator


Rear muffler


Here is where I made the cut to remove the rear muffler. I chose this location so that the muffler could easily be reinstalled with a butt joint band clamp and it worked good for the y-pipe placement.




Here is the y-pipe and dual exhaust pipes.




Custom adjustable hangers using narrow band SS exhaust clamps, SS threaded hex nuts and SS 10 x 1.5 x 130mm bolts. The bolts have the heads cut off and bent using a torch.


Exhaust pipes leading into the faux exhaust tips on the RS just like stock.


Some of the parts used. 2" SS 90° bends, 2" SS inlet/outlet y-pipe, 2" SS narrow band clamps, 2" SS butt joint band clamps.


I've now logged about 100 miles with this setup and the results are good in many ways, but more tuning is needed to refine the sound. For now everything is clamped to make adjusting and further modifications easy.

Pros so far-
Incredible power increase which is obvious right away.
Being able to hear what the engine is actually doing.
Losing over 20 lbs off the rear end.
The deep exhaust sound the little 3cyl makes.

Cons so far-
A little louder than I want it.
Some exhaust drone and resonance while under a load.

I'm looking into adding 2 small resonators or bullet mufflers (1 on each exhaust pipe after the y-pipe). I believe most of the resonance is due to the long run of exhaust pipe after the first muffler/resonator. This is why you often see resonators/mufflers near the end of the exhaust on most vehicles. Since we have a resonator up front I'm guessing the 3cyl makes some unwanted noise/resonance immediately after the cat. Adding some resonators to the rear should also cut down on the intermittent drone too.

I'll get an exhaust clip soon, just waiting for my camera to charge which hasn't been used in years, lol. My camera records sound better than my phone, so I'd rather use it for a more accurate sound clip.
 
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#54 ·
I bought the y-pipe, exhaust clamps and SS bolts from ebay, the exhaust tubing from Summit Racing and the SS hex couplers from Amazon. It was about $150-$160 for everything. You could do it for about half that if you used steel parts instead of stainless steel, but SS will last forever so I always go that route with exhaust parts.

The y-pipe is 2" ID for the inlet and both outlets so a 2" OD tube fits pretty good, but I still made 1 slot on each y-pipe connection so the narrow band clamps fit tighter.
 
#55 · (Edited)
#57 ·
The SS exhaust clamps have 10mm x 1.5 bolts, so I used a SS 10mm x 1.5 hex coupler along with a SS 10mm x 1.5 bolt. The bolts are 140mm long with the heads cut off, then bent 90° using a Mapp torch. I used the nuts that come with the clamps as jam nuts to secure the hangers once you get the height adjusted.



 
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#59 ·
Sold my Trailblazer back in January. I still have the exhaust, just not sure if I should keep it for a future project or sell as is.
 
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