Ultimate GEN1 cat / muffler upgrade: Long Winded Version

ZEUS

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For my '94 rt bone stock:

Like many of you with Gen 1's not satisfied with the stifled stock sound, I researched the sh&% out of the VCA and the Alley to come up with the best sound I could (specifically at low revs and idle) to go with the cars killer looks. If another buddy was to say "it's so hot looking, but why does it sound like a stock civic" I was gonna kill someone.

Anyways someone suggested I take off the cats ("You'll love the sound!"). So I did...no F'n difference, (maybe slightly raspier). And man it smelled especially at stops. And even if you can stand it, most chicks won't like it at all.

Decided to start from scratch without muffs and cats, just to hear what the car sounded like at its loudest for a basis. My midas guy cut the pipe before the cats and I took it for a spin (without side-covers obviously). Loud at idle but, it had a nice top-fuel dragster "gurgle, gurgle", surprising not as overly loud like you've heard all other cars without muffs. My old VW was 10x louder than this. However, as I drove, it was way too loud on acceleration, and WOT was really, really loud and really unique---wailing, wailing trumpets!!!....BUT MAN, I DID NOT EXPECT THE POWER JUMP, holy f%$#!!!! Throttle response was amazing, amazing, amazing...and third gear spins crazy man, what a rush, quite literally!!! As well it pops on decel so much and really loud too. Anyways it made me smile so much, but truly there is no way you can legally drive it with that noise.

Now to tone it down, I bought Hi flow cats from Roe (3" metal) and I took the advice from some and bought a glass pack 3" (actual red "cherry bombs") 30"long. They both fit exact distance (from cutting the original weld point of the oem cat) to the hanger before the turnout. No mid pipes necessary. Lastly Roe supplied me with the 3" turnout pipes they use in their system. (I carefully measured angle and distance of original exhaust cut-out, before I cut and installed the turnouts (Don't weld here use clamps for adjustments for placement).
Results:

The Bonus part is power. It is so much faster I can't handle it. Really, it made it a must (only now) to get some stickier rubber otherwise it spins every time I heavy-throttle it (not even WOT) with so quick a response in second and even third ("stupid" dangerous spining). The short (about 5" long) 3"diameter hi-flows are the only "obstruction" really in this system and they do an amazing job. Smells like stock now, thank God. The difference in power from no cats, no muffs is not even noticeable. It did muffle 70% of all the pops on decel (all the loud ones completely though).

The best part, the sound. It has low bassy gurgle, it has presence without being obnoxious at idle and part throttle. People hear some bassy muscle coming down the street. Now I know "likeable" sound volume is subjective, some will say that this straight pipish design is probably overly loud. But a good litmus test is what others/passersby think....yes great attention, they'll all hear that low grumble, but everyone thinks the car sounds like it is the original exhaust or the way it should've. Furthermore, I was in bumper to bumper traffic beside a cop windows down for about 5 mins with no hassles. No one questioned me this whole summer "what did you do to the exhaust", no one. HOWEVER, if you floor the throttle near that sweet spot rpm ie-3000ish...."wailing trumpets" (so original man! I and all my buds have not heard this on any car) and loud as to scare anyone on the sidewalk. Beware of police "hearing" you if you're racing in the area. But this is only around that rpm, and so normal ("mean") everywhere else (part throttle, 3/4 throttle). So you can modulate this at any time to never peak into higher revs if you wanted to be extra quiet, but it is really fine. As a matter of fact some Porsches/Ferraris etc. have an exhaust bypass at WOT for power/sound. Ours is 'natural'. But to summarize, people have never said the car is too loud, they think that this is how a Viper should sound.
Hope this helps people for their research,
-Tom (ZEUS)

NOTES:
-The original muffler is not straight through at all. It goes down to 1 5/8" wide inside...like it was a last minute idea by Chrysler to rid the WOT "wailing trumpets" that my car now has.
-Roe's 3" full system might be the same, slightly better, slightly worse. They use a borla 5" Can that like mine, is basically a straight through with the same Roe 3" hi-flow cats. A couple of people suggested a tinnier noise than the glass packs which are known to be bassier, but I'm sure they sound close.
-One thing to note, on cold start up it is raspier/louder than normal idle for a minute or so which might come across echoing into the house.
-I don't drive much with the roof on---it is not my daily driver, so drone might be an issue, but every change from stock will affect it anyway.
-I finally did the intake/filters/minus-intake-resonators just now, but increase is hard to feel with what the exhaust did for spinning tires.
-here is a video link of a quarter-mile run by Rich Detert's car...extra long glass packs (48" I believe) without cats, but only 2.5" all the way through. It sounds good (this video is the main reason I went this route) but it still doesn't come across as if you were standing curbside. http://richdetert.com/MARVideo.htm
-link for my 3" cherry bomb
http://www.supremeperformance.com/DisplayTab.aspx?tid=3
 

TheMeat

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Nice write-up!!! :2tu: I hope I can feel the type of performance increase that you described! Especially since I am doing Belangers,exhaust, and VEC1 at the same time.

The link that you posted doesn't work for me though :(

Here is the link to the mufflers that I've put in place of the cats... Moroso Spiralflow mufflers

Also, the glass pack style mufflers that I chose have louvers inside them for the exhaust to enter and are not a perforated design.

Ray.
 

randy lindberg

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Great Description. On my '94 I also cut off the exhaust at the cats. Then, went with a reducer 2-1/2" up to 3", put in Moroso Spiralflow mufflers in place of cats with a dynatech vortex cone mounted inside the Spiralflow where exhaust first enters the muffler (this really helped the drone at 1500 to 2500 rpm). Next a 3"pc. of straight pipe (6" long with about 1-1/2' inside each muffler) into a 3" Dynomax Race Bullet "glass pack" muffler. I got tips from Summitt and fabricated a hanger to acccomodate the 3" system. Lots of trial and error, but I'm thrilled with the final results. Cost me about $380-$400. (Vortex cones were pricey, but I think worth the extra expense). Lumpy, bassy idle, loud at WOT. Fairly inexpensive, great sound.
 
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ZEUS

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Ray,
I tested the links, they work for me...you have to wait a few secs.
My cherry bombs are louvered as well. We didn't know which way to place them (it didn't indicate a direction)...ended up placing the louvers with the wind ie.-openings toward the exit (otherwise, flow gets trapped?)

Your car will zoom like mad with Belangers..I can't imagine it on top of what I have (must fix sticky rubber first)... but, my gen3 buddy's car is really ridiculously loud with Belangers (vibrates all his panels!). Keep me posted.

No-cat smell doesn't phase you? I couldn't stand when passengers/bystanders would complain...I didn't want to hear it, (or buy cats really) on top of the smell on my clothes. If you go 3" the Roe metal cats, it didn't make a difference in power loss...believe it. I mean they are wider and only 5"-6" long, and you can see right through them. Pricey, but relatively cheap from Roe.
 

Roland L-Ocala FL

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Has anyone had any dyno numbers done or should I say redone after these changes? I would be curious to see what the numbers say from before the mods were done, and then after you pulled the stock cats and replaced them with Roe's cats and put in glass pack mufflers. From what you guys are saying, it jumped up the hp quite a bit, and it did not cost all that much to do.
 

ViperJames

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I did basically the same set up Roe High Flow w/ Roe exhaust...I honestly think it is TOO loud now....I love it, but when it comes to a long cruise or dinner with the wife....it is not excactly exciting...Has anyone found a happier medium?
 
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ZEUS

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James, I haven't heard Roe's Borla instead of these long glass packs...I mean I used a 30-35" cherry bomb, that video is of a car with 48" glass packs. Your Borla is only 15" long.
Maybe that's why the average joe has never mentioned my car is too loud.
-Tom.
 

XS TORQ

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Great write up!

I went from just
smooth tubes and filters
to
Valaya headers, free-flow (Hen-S-E) cats, and glass packs
and my dyno results went from 374HP to 417HP
don't have the run info here, and can't remember the torque. Torque went up about the same if I recall correctly.

I have now done heads and cam, 1.7 roller rockers, larger throttle bodies, and comp coupe mufflers.
It now makes 471HP/492TQ. It is screaming load at WOT. A bit too loud going through the neighborhood. I may try some cones in it. It sets off car alarms. In garages. The garages are about 100 feet from the street in my neighborhood. :)
 
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ZEUS

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Heads and Cam work change lowered the torque? Gen 2's say they like original gen1 torque at low rpms.
 
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ZEUS

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Roe claims 17-22hp for the 3" cats alone. I drove without cats initially (with stock ****) for 2 weeks with not much difference in power "felt" compared oem cat and ****. I wonder how much the oem muffler is really worth in HP loss. Only after replacing that stock muffler with my straight through 3" glass pack...that's when I felt ape-sh#* power, tires spinning like crazy etc..

The original **** is a power drain. (Funny thing is I think Chrysler had Borla design that piece of twisted 1 5/8"inch crap!!)
 

rpm9000

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I added Belanger headers, Roe 3" cats and Dynomax mufflers to my 95 recently. I could tell a big difference in power. The stock system is very restrictive. I plan on dynoing again soon to see actually how much power was gained. Before the mods I got 385hp and 457tq.
 

ViperJames

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I added Belanger headers, Roe 3" cats and Dynomax mufflers to my 95 recently. I could tell a big difference in power. The stock system is very restrictive. I plan on dynoing again soon to see actually how much power was gained. Before the mods I got 385hp and 457tq.

If you added the VEC2 to your mods, you would put down over 100 HP over stock. It is the best $1k you could spend at this stage of the game.
 

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