customblackbird

iTrader: (15)

Idk whats going on with my other thread so I'm reposting.

I'm fabbing my exhaust currently. I originally had a true dual 3" with Xpipe and dual 3" mufflers under the rear seats, then dual 3" over the axle with hidden tail pipes on each side. Car was pretty loud but sounded real good with a 521 but i'm going a different route. I have now ripped out the whole combo and swapped in a 150k 5.3LS bolted to the same 2004R trans. The Engine will be supercharged with about 10-12psi and should make 550-600hp in all stock form (original 99 5.3 truck motor with 150k rated at 275hp from the factory). My conversion of flow would put me in the dual 3" territory but I wanted to change that out for a different setup that followed the stock routing more. I calculated that a single 4" will work and flow enough for my needs and not really affect the max power.

So I swapped in some cheap 304ss LTs with 3" collectors connected to 3" mandrel S-bends into a Flow master dual 3" inlet - single 4" outlet Ypipe. Then I ran 4" tubing and mandrel bends over the axle and to the stock location. I was going to use a 4"x16"x6" dynomax ultra flow muffler in the stock location with a hidden tip on the driver side. After mocking it up I ran into a issue with my sumped stock gas tank not allowing the 6" case to fit level and would hit the sump causing the muffler exit to point down. Wanting to keep the car somewhat quiet I decided to order a 4"x14"x4.75" Hooker Max Flow muffler that will hopefully fit up closer to the stock tank and sump and allow the exit to be somewhat level.

Now my question is... Do I run both mufflers? I know people put the first muffler in the intermediate pipe which is perfect usually but my Driveshaft etc is too close for the 6" case and I wanted it tucked up nicely. This leaves me with really only 1 option which is to run the MAX flow muffler in the stock location and then run the dynomax ultra flow where the exit pipe would be with a short turndown at the tip below the rear bumper. Using both mufflers should help with noise and resonance I would think. Besides kinda looking alittle ***** i think it would look nice. Given the 4" DIA tubing and this being a supercharged motor the exhaust will be loud as is. Both mufflers being a 16" case and a 14" case would effectively give me 30" of muffler with different resonance frequencies.

I know from specs on the net with some real testing showed this on a 11:1 SBC motor.

For reference, a 14 dB increase doubles the sound level, while 60 dBs represent normal conversation and 90 dBs are considered the threshold for pain.

1. Borla XS 80db at idle, 90db at 2,000 rpm, 110db at WOT.
2. Hooker Maxflow 80db at idle, 90db at 2,000 rpm, 120db at WOT.
3. Magnaflow 82db at idle, 91db at 2,000 rpm, 114db at WOT.
4. Flowmaster 82db at idle, 93db at 2,000 rpm, 115db at WOT.
5. Flowtech Warlock 83db at idle, 92db at 2,000 rpm, 112db at WOT.
6. Dynomax UltraFlo 83db at idle, 94db at 2,000 rpm, 113db at WOT.
7. Borla XR1 83db at idle, 96db at 2,000 rpm, 118db at WOT.
8. Bassani Street 83db at idle, 96db at 2,000 rpm, 120db at WOT.
9. Edelbrock RPM 84db at idle, 93db at 2,000 rpm, 118db at WOT.
10. Bassani Real Street 84db at idle, 96db at 2,000 rpm, 120db at WOT
11. FlowtechAfterburner 86db at idle, 94db at 2,000 rpm, 115db at WOT.
12. FlowtechTerminator 86db at idle, 94db at 2,000 rpm, 119db at WOT.
13. Hooker Aerochamber 87db at idle, 94db at 2,000 rpm, 114db at WOT.
14. SpinTech 87db at idle, 97db at 2,000 rpm, 116db at WOT.

15. No Muffler 91db at idle, 103db at 2,000 rpm,

120+db

120+db

.

Combined these should really quiet things down even for a 4" exhaust. What do you guys think? Here are some pics to show where I'm at with the dynomax mocked up in the location it would be.

Rich92 RS

iTrader: (16)

Curious to what you ended up doing? Im going from true duals to a single 4" and Im also concerned with how loud it'll be.

89gta383

iTrader: (5)

Run both. I just added another 4" ultra flow to my car and wish I had space for 2 3" mini bullets in the y-pipe.