colorado2500hd

Hi All,

I'm thinking about putting the stock muffler back on, but I'm worried about restrictions. I have a 2003 2500hd with TSP stage 3 high lift cam, 1 3/4" long tube headers, and had TSP re-do the heads with their stage 2.5 I think they call it (porting with larger valves), Magnaflow wide body muffler, with stock cats and dyno tuned. Makes a disappointing 314 at the wheels, but still better than stock.

The noise in cab is awful. I have 2 resonators on there, both after the muffler (no room to install any pre-muffler): one pretty long no-name resonator from an exhaust shop, one Ultraquiet. The exhaust is standard 3 inch. I don't think it's really that loud outside the truck, but inside is driving me crazy. I like the sound 20% of the time when I'm putting my foot into it, but the other 80% it's too much. Especially when hitting the trails and staying in 1500-2500 RPM it's just brutal.

An exhaust shop told me if I put the stock muffler back on that it would blow out because the truck moves so much more air. I don't know if this is true or not, but I don't know anything about exhaust: I would think the stock cats would be more restrictive than the muffler, but I don't know. Every exhaust shop tells me the only option to quiet it down is to swap the muffler. Also, the tune was done with the Magnaflow on there, but I don't know how much of a difference that makes.

Looking for some advice from anyone who knows more about this exhaust stuff than me. Want to quiet it down without messing anything up or losing power. New Colorado emissions laws so I have to keep the cats.

Thanks!

RDF1

314 isnt bad at all.
I dont have any cats and just running a big dynomax muffler and its very nice.. Very little noise at 70mph / 2400 rpms.

Does your tail pipe exit out from under the bed?

swathdiver

I would say with 314 horses, you're not moving enough air to blow out the muffler. Ditch the cam and heads to get your power back and begin again from there with a good tune.

adriver

iTrader: (1)

Do you have any way to test the decibel level you are getting in the cab that is too much, just so were on the same page? Without a number its relative to what is too much.

I don't have them, but isn't the cab noise being made, mostly coming from the long tubes?

There are many resonators out there that are only slightly larger than pipe, they will work much better if before the muffler, if they are even doing or going to do anything at all.. The resonator isn't there for noise overall, it's supposed to be tuned to stop the drone that's being caused at a specific frequency / RPM. They may really not be helping anything. If you are getting drone at a certain RPM, then you probably need to fix one.

Magnaflows in general are not a quiet muffler. You could definitely swap to a different manufacturer and maybe the style of muffler. Chambered mufflers are designed to stop a specific frequency range (high or low) to "clean up" your exhaust sound. If its a low or high pitched tone specifically that is bothering you, that could easily be fixed by the right muffler. Straight through mufflers are generally loud and flow the best, (but you don't need to go all out with what you have if you don't want that).

If your exhaust tips are pointed at the ground, you will get more sound bouncing off the ground, and if straight down, then into the cab.

Here is some stuff I recently found. There's a way to use your engine numbers and some math, and you could see if those mufflers are choking you out. My guess is they are.
Complete new exhaust, and I think I need to modify the cats. - Page 2 - PerformanceTrucks.net Forums

If it was me: I would put some better mufflers on there, keep the mismatched resonators off, (until you see if you even need them), and run pipes out the back with the tailpipes pointed straight out the back.
(I had magnaflow and flowmaster mixed up and edited some of this out).

EDIT: How is your piping routed? Are you completely straight through? Perhaps someone else can answer, but with the ported, higher flowing heads, wouldn't OP do better with a X pipe or some scavenging?

colorado2500hd

@RDF1 - exhaust points slightly downward at an angle right below rear bumper on passenger side

@swathdiver - maybe I'm not understanding, why would undo everything I just did, and buy new heads?

@adriver - thanks for the reply, that list is very helpful. The noise is definitely from the muffler, it's been there since before I did the headers, it's always been too loud. The noise is definitely a drone - at 3,000 rpm it's great. Exhaust pipe is somewhat pointed at the ground, more of an 45 rather than a 90.

RedXray

This may sound crazy but after doing my floors and bulkhead in Kilmat over the weekend my junk went from a loud obnoxious redneck truck to an upscale quiet sophisticated enjoyable piece of junk on the inside. 1 7/8" headers, two Vibrant resonators, two 14" Magnaflows with rear rollpan exit (no cats). Hard believe the difference, makes driving enjoyable even more so.

silentbravo

iTrader: (1)

You did the floors and rear firewall then @RedXray ? Any other panels like doors or roof with sound deadening? I need to do my interior, but wasn't planning on the floors. I figured the carpet and carpet pad had pretty good sound dampening, but I'm sure there is room for improvement there.

RedXray

Yeah floors and rear bulkhead. The doors are next when I get a few more pieces of mat. Not going to do the roof because my headliner is perfect and messing around with a delicate 22 year old headliner kinda scares me. It's quiet inside now... almost to quiet for a hotrod.

swathdiver

Because you are way down on power, that combination of parts is not producing the power it should. The proper way to find out is to take the stuff off and start over, making one change at a time and measure the performance. My Gen IV 5.3 puts down 307 RWHP through the traps in the quarter mile and it is stock save for a BlackBear tune, no fancy air filter, exhaust, headers, nothing but new cats and y-pipe. All that stuff on yours should blow me away.

adriver

iTrader: (1)

I have done my entire cab. I did the doors first. That helps put the barrier between your music and the outside world. The doors help block out most of the "other people caused" noise. The back cab half wall and floors are going to help block out the EXHAUST, engine, tire, and road noise, (the noise your truck is making). The roof helps to kind of finish up the cocoon of sound dampening. I would guess I get a 15db drop from the outside noise. I would compare it to sitting in your house, and watching tv with the windows open. Do it for 30 minutes so your ears adjust, then go close the windows. You can turn the tv / your truck stereo down, because there is less competing noise. Your ears can relax, and you can block out the garbage all those other idiots are listening to.

I have a $3K system in my regular cab pickup, (2K watts, 3 amps, some ridiculously overpriced (but clear) component speakers). I can do 90 with the windows down, sing as loud as I can and drowned myself out. I really enjoy my LOUD music. After I did this, I spent 3 months with it off just because I appreciated being ABLE to have it quiet when I drive. I keep the stereo off, more now than before I installed the sound deadener. I can get annoyed quickly at other drivers, (/ can be an *******), and I think having this option has calmed me down as a person. If this is in the plans, this will DEFINITELY help.

Its a thin hard material, IIRC fiberglass frame, but the only thing to worry about is when it falls and the pillars. The A pillar clips on the top are really strong and (from what I found on mine and everything in the yard), those clips generally will break off if you don't use a trim tool. I even ripped a crack down the bottom of my C pillar when I went too quick once. The tabs holding those on are pretty weak also. IIRC 7 tabs or holding each one, and there's a reason I don't think you will find one with all of em still attached. Not sure if heat or cold would help pull those off, but the A and C pillars are more likely where you will cause damage.

I remember I had to find a youtube video on how to pull the hooks off. IIRC they were really tight, but you have to pull them forward (at their angle), then they will pull out. Once you get all the plastic off the roof panel, it falls right out. There are no clips or anything holding it in that can damage it. If you can find something to help support it while you are doing that, you shouldn't damage the headliner at all. Two minutes to pull the plastic trim if you have done it, and a 2 person job to support and pull out the headliner if that's an option.

The roof doesn't do as much as the floors or doors. I liked the doors because when you close them, it gets rid of the "thin tin" sound you get when closing em. It makes them feel and sound a bit more solid, (as if it inspires "build quality"). The roof will get rid of the rain "ting". Quiet down airplanes flying over head. If you live in a city where there's activity above this would help. It's definitely the least and last of the three areas.