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[TABLE="width: 578"]
[TR]
[TD]TRUBENDZ 04-08 Pontiac Grand Prix Dual Exhaust Tubing System[/TD]
[TD="align: right"]$170.00[/TD]
[/TR]
[TR]
[TD]WALKER 17666 Dynomax Super Turbo Direct Fit Muffler RIGHT[/TD]
[TD="align: right"]$69.99[/TD]
[/TR]
[TR]
[TD]WALKER 17667 Dynomax Super Turbo Direct Fit Muffler LEFT[/TD]
[TD="align: right"]$69.99[/TD]
[/TR]
[TR]
[TD]WALKER 21569 Exhaust Resonator and Pipe Assembly[/TD]
[TD="align: right"]$42.79[/TD]
[/TR]
[/TABLE]

all of those are the 2.5" pieces, including the OEM replacement resonator assembly.
 


Instead of the walker resonator you could just put in a glass pack. It will probably last longer than the Walker one, and you can put one as long, or short, as you want.
 
stealthee said:
Instead of the walker resonator you could just put in a glass pack. It will probably last longer than the Walker one, and you can put one as long, or short, as you want.
Click to expand...

i hate glasspacks, complete waste of money IMO. I have had about 5 of them over various cars none of them ever changed the sound by a decibel.
 
Spawne32 said:
[TABLE="width: 578"]
[TR]
[TD]TRUBENDZ 04-08 Pontiac Grand Prix Dual Exhaust Tubing System[/TD]
[TD="align: right"]$170.00[/TD]
[/TR]
[TR]
[TD]WALKER 17666 Dynomax Super Turbo Direct Fit Muffler RIGHT[/TD]
[TD="align: right"]$69.99[/TD]
[/TR]
[TR]
[TD]WALKER 17667 Dynomax Super Turbo Direct Fit Muffler LEFT[/TD]
[TD="align: right"]$69.99[/TD]
[/TR]
[TR]
[TD]WALKER 21569 Exhaust Resonator and Pipe Assembly[/TD]
[TD="align: right"]$42.79[/TD]
[/TR]
[/TABLE]

all of those are the 2.5" pieces, including the OEM replacement resonator assembly.
Click to expand...

That is too expensive in my opinion for mufflers that are not fully welded. I have used Dynomax in the past, the sound is decent with a bit of a nice growl, but they dont last as they end up leaking at the seems. As we discussed before also in my opinion 2 1/2 is too small for our cars, but get what suits you.
 
rottonj said:
That is too expensive in my opinion for mufflers that are not fully welded. I have used Dynomax in the past, the sound is decent with a bit of a nice growl, but they dont last as they end up leaking at the seems. As we discussed before also in my opinion 2 1/2 is too small for our cars, but get what suits you.
Click to expand...

I'd happily buy a 3" exhaust, if you could prove to me that there is a gain by going to a 3" over a 2.5" dual. lol
 


On stock horsepower levels, the 2.5in tubing is fine. You are only making 300 crank HP. And the split to two 1 7/8th exit pipes does help already.

My silverado has 2.5in pipes off each manifold into a single 2.75in catback system and makes 330-340ish crank HP with a tune and thats enough flow.

The issue is the manifolds on the LS4, replace those and the downpipe and you are just fine.
 
Fivefingerdeathpunch said:
On stock horsepower levels, the 2.5in tubing is fine. You are only making 300 crank HP. And the split to two 1 7/8th exit pipes does help already.

My silverado has 2.5in pipes off each manifold into a single 2.75in catback system and makes 330-340ish crank HP with a tune and thats enough flow.

The issue is the manifolds on the LS4, replace those and the downpipe and you are just fine.
Click to expand...

His car is not stock, has a cam, headers with a modified induction system and a intake in the works.
 
Spawne32 said:
I'd happily buy a 3" exhaust, if you could prove to me that there is a gain by going to a 3" over a 2.5" dual. lol
Click to expand...

Be stubborn :), I cant provide it other than stating I have used 3 inch exhaust systems in the past on cars with one main section pipe with seat of pants gains. I can tell you going 2 1/2 will net you nothing as its what is there already except for the smaller tail section. Whatever you choose I would include some brand of welded mufflers if you want it to last awhile.
 
rottonj said:
Be stubborn :), I cant provide it other than stating I have used 3 inch exhaust systems in the past on cars with one main section pipe with seat of pants gains. I can tell you going 2 1/2 will net you nothing as its what is there already except for the smaller tail section. Whatever you choose I would include some brand of welded mufflers if you want it to last awhile.
Click to expand...

General rule of thumb is to size your exhaust by engine output CFM, roughly 2-2.5 CFM per horsepower, so for the 5.3 I estimate somewhere around 350 crank horsepower. Which generates roughly 700CFM of gasses into the exhaust system. While you could argue that the small section of 2.5" pipe coming off the 3" downpipe isnt sufficient enough (as 2.5" pipe generally only flows about 500cfm), i still stick with the dual exhaust formula, and even then a 2 1/4" tail section would still be adequate enough for the 5.3 in this case. So im still a firm believer that increasing the size of the pipes to 2.5" straight through to the tail and getting rid of that small reduction section in the back is still more then enough CFM flow for this engine. I like to undersize them slightly vs over-sizing because the lose of torque and low end from over-sizing is more significantly noticed vs the loss of "potential" horsepower gains from running slightly larger. Not to mention the fact that you have to consider the fact that running a cat as well, is still really the big restriction in the exhaust, which dwindles the gains from a catback even further. Most of my restrictions in the LS4 exhaust system have been eliminated largely by increasing the size of the primary's, adding length, and increasing the size of the crossover and downpipe by a significant amount.
 
You cant use the dual exhaust formula, its not accurate for our cars system. You could lose a little torque and low end, the car blazes the tires right off the car as it is lol. I say better to go bigger than do it again. I'm really surprised you are running a cat, I didn't think you had to for emissions in your area? The 2 1/2 to me isn't worth the time or money.
 


rottonj said:
You cant use the dual exhaust formula, its not accurate for our cars system. You could lose a little torque and low end, the car blazes the tires right off the car as it is lol. I say better to go bigger than do it again. I'm really surprised you are running a cat, I didn't think you had to for emissions in your area? The 2 1/2 to me isn't worth the time or money.
Click to expand...

I run the cat for two reasons, primarily noise, because remember I drive this car every day, long rides on the highway with a droning sound are quite annoying. Two being that we still have to pass visual inspection, while i could run a fake cat, again my primary reason is for noise. The one I have on there now is a 400 cell but you can get them as low as 100-200 and 300, problem with those is they dont really do anything and you just wind up with bad cat smell.
 
Yup, know all about the fake cat. Played that game for years battling the emissions police with every car . I got old and lost my will to fight them lol.
 
Lol, why did you even bother getting a cam and headers if your going to undersized the rest of everything else proven gains from a Tru 3inch are there. Same with you still using the stock maf and such. Just because it can flow a given cfm does not make it optimal. I'm not even cammed yet my system is full 3inch, while the powerror band has shifted slightly higher, I'm also liking that car isn't being chocked when i punch it. Also you running a single cat 300 cell type is not that restrictive, at most your losing 2whp.
 
blueguy said:
What police officer seriously goes under the car and looks for a converter? lolol
Click to expand...

its NJ inspection. they look with a HD color cam in the floor, they drive over the cam and watch it on a 32 inch monitor here.

they also have road side check points too in my county. if your over due or have a failed sticker they will pull you in and inspect your car for you,,,,and dole out tickets as needed. ( they are looking for a cat)
 


So, is it infrared or xray to see if there is something inside the converter case?

Like...they'd know right away if you have a hallowed out cat?

That's nuts.

Here's Missouri: Headlights? They work. Horn? Yup, it works. Start it up. It's kinda loud? Must have mufflers. Go and flip on the blinkers and wipers. Got it? Got it. Good. Here's your sticker. Bye.
 
blueguy said:
So, is it infrared or xray to see if there is something inside the converter case?

Like...they'd know right away if you have a hallowed out cat?

That's nuts.

Here's Missouri: Headlights? They work. Horn? Yup, it works. Start it up. It's kinda loud? Must have mufflers. Go and flip on the blinkers and wipers. Got it? Got it. Good. Here's your sticker. Bye.
Click to expand...


they literally dont care what type of cat it is. all they care is if its there or not....i tried to pass cat less. they had my hood open the mirrors on sticks out, and they failed to find it lol so i failed.

NJ used to be the worst state to pass inspection. now they hardly care about the over all condition, just that the cel is off and it has a cat.

i passed with a busted side view mirror, rather bald-ish tires and a few lights out.
 
91parkave said:
Lol, why did you even bother getting a cam and headers if your going to undersized the rest of everything else proven gains from a Tru 3inch are there. Same with you still using the stock maf and such. Just because it can flow a given cfm does not make it optimal. I'm not even cammed yet my system is full 3inch, while the powerror band has shifted slightly higher, I'm also liking that car isn't being chocked when i punch it. Also you running a single cat 300 cell type is not that restrictive, at most your losing 2whp.
Click to expand...

Yes and your car also isnt fast, so there's that. So if your gonna ham it up, throw up some dyno proof that your 3" exhaust somehow net you some ridiculous gain over a 2.5" exhaust and id be willing to concede the argument to you. The reason im still on the stock maf is because im still on the stock intake, and my intake manifold and MAF swap is sitting in my garage waiting for the spring. I'm running a 400 cell thunderbolt cat, and im pretty sure my car isnt being "choked" either when I punch it, like i said, there probably is a gain to be had, but minimal at best going from the 2.5" to the 3" and the increase in noise isnt worth the price and performance gain.
 
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