Full Exhaust vs. Catback vs. Fabricate

[huklebuk]

Hi all. I have been looking at exhaust upgrades. Anyone use a Gibson exhaust? I looked underneath and there is like 4 cats and 2 mufflers. Would it be hard and cost effective to just get parts and put a new system in with fabrication? I have access to all the tools I would need. I was looking at the gibson split exhaust (catback) but it seems like $420 is alot for just a muffler and pipes with shiny tips on em. And I cant seem to find a full ready to install system. Also does anyone know the diameter at the headers so I have a place to start? Thanks.

 

[green03]

What year model is your truck? I picked up my tailpipe through a local muffler shop. It is 3", mandrel bent, polished stainless tip, made by IMCO. I then used a magnaflow single in/out muffler similar to the one they include with their complete kit for my truck. I fabbed everything else up from scratch including an equal length y pipe and replaced the factory 4 cats with 2 high flow units from dynomax. After replacing the cats the exhaust was too loud for normal driving so I added a Twister race muffler/resonator behind the magnaflow to quiet down the girl just a bit. Has a really nice mellow tone to it now. Almost sounds like one of those Nissan Zs at part throttle. It sounds very uncharacteristic for a v8 truck, but I really like it.

Matt R

 

[huklebuk]

I have an 02 EB. I didn't realize it had 4 damn cats! I guess I need to take a good look at it. Did you use any of the stock pipe, or did you fab everything? I also wanted to go to a dual pipe, but the catback from gibson and everyone else are like $400 so I don't think its worth the money. Do you think I could use some kind of a kit (i think i heard someone say you can get them at a muffler shop) that just has all different parts in it and make something work? Im in brooklyn, so going somewhere and having the work done, I'm leary about. They wanted 180 just to diagnose a broken radio, so the prices up here to get shit done are outrageous. I'm trying to save some money so the wife doesnt have a wife freak out moment when the bill comes!

 

[green03]

I buy my mandrel U bends from summit racing and cut and weld to the desired curves. You can reuse most of the stock pipe if you do this.....
Eliminate the front cats, you will need to use some bends here. Put the new high flow cats in the first straight section (where the pipe goes straight). You will need to re-locate the rear oxygen sensors to behind the 2 new cats instead of in front of the old rear cats.
You can use the magnaflow y pipe section (really nice part) or you can fab up your own like mine.
The equal length is alot of work and I really don't think it is worth the effort but it does make it sound nice.
You might see if IMCO offers a performance exhaust cat back for your truck. The part in front of the cats you can fab up but you won't gain a whole lot (i would just replace the y pipe section) unless you have some serious mods planned.
Matt R

 

[green03]

http://www.grabthepower.com/ is IMCO's site. They are sold through most of the muffler shops across america. Their stuff is pretty cheap and really good quality...... and for some reason my picture won't attach.
Matt R

 

[pronstar]

I agree...cat-back kits are a bit pricey for what you get.

If you can fab up the tubing, that's a great alternative.

But even if you can't, a good muffler shop can fab-up a system, typically for a lot less than the cost of a cat-back kit.

Tubing is all the same just pick your muffler.

I would suggest a replacement y-pipe/collector (where the pipes merge) if you have a single-outlet system. The factory one sucks and is very restrictive inside. You can get one for about $30.

 

[huklebuk]

Wow good info fellas, thanks. Is there room to run a duel exhaust all the way from the headers to the back? Of course thats gonna be alot of work. I can see this is going to be a project either way, so I might as well have some fun with it. Is there any advantage running duel, or will the y pipe do just as well or not a noticable fall off? More questions to follow, stay tuned for more threads from yours truely, I'm just too tired to start tonight.

 

[green03]

A single 3" exhaust is more than you will ever need unless you do something really ludacris (not the rapper....LOL)

2.5 inch has an area of 4.9 inches so you have 9.8 sq inches of flow area for dual 2.5 inch pipes.
3 inch has an area of 7.065 inches

Now those calcuations give approx... flow potential difference. With even high flow cats you will lose the flow of the 2.5 inch pipes full potential so a single 3 inch pipe and straight through muffler (like a maganflow) should flow about the same as 2 2.5 inch pipes with cats on them (even high flow).

True duals is hard to do on the 03 and up because the fuel tank is on the driver's side of the truck and the rear suspension is a nightmare to get the pipe around/through. I'm not sure on the older ones.
Matt R

 

[ELVATO]

So you guys are saying that all that is really needed to be changed in an 03 would be the Y pipe, and maybe the mufflers.

Just go to muffler shop with those parts, and say "I want a refab?"

 

[pronstar]

I'd shop around to a few shops. Tell them what you want and they can come up with a price. Many shops will cut you a little bit of a break here or there if they get to do the labor and sell the parts.

 

[huklebuk]

Ok. So here is what I have come up with. I buy two cats and a muffler. I do have a question on the size though. Stock I am guessing (educated) is 2.25 in/out? So should I step up to a 3" inlet and outlet? Or just leave it at 2.25 and go 3" outlet and on back for the rest? What would I have to get to attach it to the headers? I feel like such an idiot, I've never really worked on exhaust systems because I could never afford it, not that I can really afford it now but, whatever. Oh and I also got the bright idea, since the cat pipes meet right ahead of the muffler, would it be all right to use a dual in/out muffler instead of a y pipe and single? I plan on going from a single to dual exhaust anyway, sot I planned on putting double out muffler on anyway, mostly because I like the look.

 

[pronstar]

First, check your local smog laws. I think NY has the same rules as CA...do they also have a visual check in NY?

In CA, if they see that you are missing the two front cats, you fail. That's why I simply gutted mine out, so it appeared that they were on there.

Also, are your factory cats good? I wouldn't bother replacing them if they were funcitioning OK. They aren't that restrictive IMHO. I replaced mine because a bad tune fouled them, but if that hadn't happened I would still be running the factory cats.

Stock tubing should be 2.25-inch, but wait to see what green03 posts because I think he'll know for sure.

2.25-inch duals all the way back to the y-pipe/collector is good. Then you can open up to a 3-inch after that.

Dual-in/dual-out mufflers are cool, some of them have a crossover/x-pipe in them as well.

If you want the look and minimal installation headaches, I'd put a single-in/dual-out muffler on. Running duals all the way back is a PITA...basically twice the work.

 

[green03]

What year model are we talking about here. The pipe on the 03 and up use 2.5" OD primary with 2.75" tailpipe. Kind of a strange setup. The most improvement IMO would be simply replacing the factory Y-pipe section with a magnaflow piece and adding a good cat-back system. The Cats aren't worth the trouble on a naturally aspirated truck and won't be much of a restriction at that HP level and actually will keep things quiet. On the 03 the second set of cats aren't monitored so if they were to be hollowed out then it wouldn't cause and adverse effects but there would need to be some cutting/re-welding to get to the rear of them anyway.
Matt R

 

[ELVATO]

Ok, Y pipe replacement it is They are rather cheap.

Any special size requirement?

 

[huklebuk]

Ok, so I just got finished shopping. Heres what I went with on the upgrades list: For the exhaust, I got 2 magnaflow high flow cats, and a flowmaster series 50 suv dual in/out. I went with the dual in/out because I was going to have to fab to get a y pipe in anyway, so i just eliminated the y pipe. I'm gonna run dual pipes straight out the back, right next to the tow hitch frame, and I might throw on dual tips on each side, just for a different look, havent decided yet. I'm going to gut or remove the front cats, whatever is easier once I start. Under the hood I went with the AEM Brute force cold air intake, jet throttle body spacer (stiffle your snickers please, got it for the sound), and a spark plug change, gotta pick them up later. And for the suspension and body, I got a 3in body lift kit with gap guards, Pro Comp ES9000 shocks with a steering stablizer, airlift rear air springs with the onboard air compressor and cab control, a 2in coil lifts for the rear and a set of 35 X 12.5 X 17 Pro Comp AT tires. Just ordered today, going to begin install around the 20th, figure 2 weekends and I'll have everything done. All to the tune of about 2 large. Credit is great! I'll take some before and after pics so you can see the changes if your interested, I have no idea how this is going to turn out! Hey Matt, hows about a tune up?

 

[pronstar]

Damn, you don't mess around!

 

[green03]

Now you need a good programmer to fix the speedo and tune for the exhaust and intake upgrades.... Hint Hint
Drop me a PM!

Oh and just make sure your rear O2 sensors are behind your new cats otherwise you will throw a code, but then again that can be eliminated in programming as well.....

Matt R

 

[huklebuk]

No, I don't mess around. This is my first really serious venture into doing anything major to anything, because I could never afford it. Now here is the kicker and why I'm not concerned with emmissions laws: Although I live in NY, my tags are still in NC because I am in the military. I don't have to switch, the funny part is I have a NC registration on it with a Brooklyn address! So I don't go through NC emmissions, nor do I go through NY emmissions. Best part is I spend about 50 bucks a year tagging 2 vehicles and my motorcycle. Ok back on subject. Matt, I sent you a pm a while back. I'll resend.

 

[huklebuk]

Originally posted by green03
Now you need a good programmer to fix the speedo and tune for the exhaust and intake upgrades.... Hint Hint
Drop me a PM!

Matt R

Clean out your pm box.... its not accepting anything! How much am I looking at for a tune? Does it involve a chip?

 

[green03]

Okay... PM box cleaned out!
sorry about that.

I'm still not getting notifications of of thread responses and PMs to my email.... I wonder what is going on...