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Discussion Starter #1 (Edited)
The second muffler finally came in so I went down to the shop yesterday evening to have the system put on. The idle RPMs are a little high in the "Before" sound clip because it was recorded as I was leaving for work.

Before
After
Added sound clip:
2nd gear dyno run ... 2600-6500 RPM

It is definitely NOT the Road Runner - but I like it.

I'll have pics up by tomorrow - I hope - along with the details ...
 

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Why so large?
 

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Discussion Starter #5 (Edited)
We start where the 2"+ pipes come down from the cats and go into the Y-pipe ...


Followed by the first muffler, a 3" Dynomax UltraFloSS - notice the "custom" rock-catcher on the front ...


Then there's the 3" mandrel bend tubing from TrueBendz - along with the old system ...


and the Flowmaster DeltaFlow 40SS (#843043) behind the gas tank ...


And lastly, we have the Flowmaster polished SS tip with the rolled edge ... I'd never seen a clamp-on tip before - kinda' odd.
 

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Discussion Starter #6
hypnos said:
Why so large?
The 3.5 is almost exactly half of my 440 in both HP and displacement so this system is half of what my 440 exhaust will be after the re-build. Actually, the 440 will only make about 450 HP, not 500. Insane logic? - I'll let you know after the dyno. I did run the dual 2-1/4" pipes back as far as I could ... hopefully it's far enough.

mlfca said:
Do you get the 2000-3000rpm roar noise?
There's quite a bit of resonance from the trunk right now and I'm still thinking about adding a resonator tip to tone it down a little bit. But the trunk liner I got from LOUD98ES will be going in tomorrow - that may help a lot. You'd think two mufflers would be enough! So far, I've only had a day to listen to it - give me a week to really get used to it and get the liner in - then I'll let you know. I like the sound from the outside, it's the inside noise when I'm on the pedal that I'd like to loose ...
 

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All I can say is: dayuhm! That's one nice setup. Dynomat the trunk, forget the resonance. You wanna hear that exhaust, not tone it down. :p
 

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Nice set-up.

I was wondering what the noise was like with this set-up. I'm currently running the stock resonator in front (where your y-pipe is lcated) and the Magnaflow in back. That stock resonator is going someday, and I'm wondering if I should look at something to dampen the noise, or just replace with a y-pipe and call it a day.
 

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Discussion Starter #13 (Edited)
sconnelly said:
Nice set-up.

I was wondering what the noise was like with this set-up. I'm currently running the stock resonator in front (where your y-pipe is located) and the Magnaflow in back. That stock resonator is going someday, and I'm wondering if I should look at something to dampen the noise, or just replace with a y-pipe and call it a day.
Getting rid of the factory resonator is probably a good thing (I'll let you know after the dyno runs) but - IMO - you need a second muffler/resonator ... unless you want it LOUD.
I've only had it on one round-trip to work, which is mostly freeway - I need more time with it to give you a good opinion ...
 

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Excellent work, who did it? While your system may not be exactly perfect for backpressure as far as balancing torque and horsepower, it sure is unique and hell, it sounds real good from here, and that's not even in person, so kudos to you!
 

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Discussion Starter #15
Axle said:
Excellent work, who did it? While your system may not be exactly perfect for back-pressure as far as balancing torque and horsepower, it sure is unique and hell, it sounds real good from here, and that's not even in person, so kudos to you!
Thanks! A local shop did it - same guys that installed the 2-1/2" duals on my 72 Sebring. Everything I've seen says I should have lost torque on that set-up, too, but I didn't. Even though it's only a 318-2v ... I gained some by up-sizing from 2x2-1/4". Before the 2-1/2" system I could barely chirp the tires, now it burns about 15'. Not bad for a stock 318 w/225's on it.

As for the balancing - we'll see what happens on the 5th when I dyno it again. I would have preferred 2-3/4" instead of 3". But I think the 2-1/4" pipes are running back far enough to make it to the proper cross-over point - though I must admit I relied on Chrysler Engineering for that (300M Special as intrepitor noticed).
 

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The benefit from the slight upsizing on the 318 is to be expected because, as I'm sure you know from personal experience, those things were chocked by the exhaust, especially at higher engine speeds. Furthermore, it wasn't a tremendous upsizing, just a quarter inch in diameter, which is actually the same thing that should have been done on the Intrepid, a cat-back 2.5" if going by the cookbook for balanced exhaust systems. A dyno might not show the difference you're looking for because the reading is taken in 3rd gear, supposing it's a standard dyno, and clearly, the engine's output is different in 3rd gear than it would be in 1st due to different engine speed, but just for comparison's sake, do you have an initial dyno on the Intrepid or do you at least have a copy of one to see a before and after?
 

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Discussion Starter #17
Axle said:
The benefit from the slight upsizing on the 318 is to be expected because, as I'm sure you know from personal experience, those things were chocked by the exhaust, especially at higher engine speeds. Furthermore, it wasn't a tremendous upsizing, just a quarter inch in diameter, which is actually the same thing that should have been done on the Intrepid, a cat-back 2.5" if going by the cookbook for balanced exhaust systems. A dyno might not show the difference you're looking for because the reading is taken in 3rd gear, supposing it's a standard dyno, and clearly, the engine's output is different in 3rd gear than it would be in 1st due to different engine speed, but just for comparison's sake, do you have an initial dyno on the Intrepid or do you at least have a copy of one to see a before and after?
I was going by the Flowmaster chart for exhaust sizes - it lists 300-350 CID up to 250 HP as 2x2-1/4". That's what it had on it when I bought it - including the headers ... I just upgraded the pipes to 2-1/2". That's what my 440 is running, too, for now.

As for the dyno runs, all mine were done in second for two reasons ...
1. I wanted a wider range to test the mods I was gonna' do - 3rd gear has a forced shift at 5700 RPM, and
2. Having never done them before I didn't know I was supposed to use third (1:1 gear ratio).
I come from a poor hotrod neighborhood ... racing was our "dyno" ... :biggrin:
 

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Discussion Starter #19
Axle said:
Kind of off-topic, but what were the 318 and 440 connected to, 727 or 904?
The 440's got a 727 with a B&M shift kit and pan. I'm not positive about the stall speed - I think it's 2500 ...
The engine in the Sebring is from the mid-80's (with the closed port heads). The guy before me swapped it so he may have swapped out the tranny, too. I haven't played with it very much - just some little things like the exhaust (which needed replacing) and some body work (still not complete).
 
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