So, you want even MORE flow than a Random Technology Cat huh?

[Viper Specialty]

Well, thats EASY! Or...not so easy as I have found out. As some of you know from my earlier posts, I had a RT cat fail a few weeks back. Well... I found out soon after my Passenger was coming apart too. Hmm... do I no longer trust RT? You better believe it. I didnt even get 3 months out of them, and I was always running a wideband, well within the parameters of what they are designed to handle. Between the 2-week wait PER SIDE, and the out of pocket expense until THEIR decision what had happened, it wasnt worth the hassle. So, I built a better mouse trap.

As many of you know, and some don't, the SRT comes with 4 Catalytic Converters. The two upstream are Ceramic Substrate, and the two downstream are Metallic Substrate. Let me say that again; The two downstream are METALLIC SUBSTRATE. You know, that goofy bonus you paid RT an extra few hundred bucks for? And, get this: The STOCK CATS are actually a 5" diameter substrate, while the RT cats are only 4"! What does that translate to? That means the STOCK CATS have 160% of the Cell-Surface area of the RT cats! Before some of you knowledgeable people call it, yes, the CPI (Cells Per Inch) is the SAME as RT. The key to getting the flow out of the stock cats is the size piping used with them, and cutting down the number from 4 to 2. The primarys are high flow, too, but from what I have seen, they start to come apart FAST. my pair was already showing signs of cell fracture at 12000 miles, with various cells plugged as a result. Not nearly enough to cause a problem- but you could bet your bottom dollar by 25000 miles it would cost you some power if the rate remained the same.

Well, thats just the parts. Getting it into the car is a whole 'nother ball game. Unfortunately, at this time, there does not appear to be any way to even get the parts to do this unless you have a set of RT cats first... as the correct 3" pipe, lip, bend, and hangers are all part of their setup. However, for someone who ever has a set fail, this is certainly the way to go:

Three things are a MUST before you would even attempt this.

1. Patience. It takes a LOT of it to get the angles correct, lengths, etc.
2. TIG welder and experience using it. MIG is not a good choice at ALL in close proximity to a Catalytic converter with an Edge-To-Edge weld. Mig's produce far too much splatter, wire blow-through can break off later end end up in the core, as well as Flux-Cored Mig wire can poison the core itself.
3. A GOOD Carbide cutting disc and files to prep pipe-ends.

I may offer this service over the winter if I show dyno gains from it. Anyone who has RT cats could send me the full assmblies, and I would install the OEM's. The RT cats would still be sellable on Ebay for a hundred bucks or so each if in good shape. I may also work with RT or someone else to get bare pipe assemblies ready for installation.

SKIP- They sure are Cats! I hope you still have them all!!!

 

[KaiPL]

Very interesting. I'm glad I kept all of my old exhaust stuff after installing the Corsa Track system.

I have no idea which cats are which. Could you please post pictures of the stock ceramic and metal subtrate cats and identify which part is which?

 

[SylvanSRT]

seems like a lot of effort/labor to make this change and run cats. why not just go cat-less. unless you live in a state w/ emissions testing? and will the car pass an emissions gas test w/ the modded exhaust anyway? no cats should yield more hp and flow correct? also more volume(loudness).

 

[Paul Hawker]

Many have reported that catless Vipers smell like rotten eggs. (Maybe that was only with one cat).

 

[Viper Specialty]

Catless doesnt stink like rotten eggs, but it BURNS your nose and eyes sometimes, especially in the SRT. Cross-winds/backwinds in slow traffic can make it unbearable quite easily.

Also, going catless has its other downfalls, such as a completely different tone. the exhaust pitch is much higher and raspier without them... dare I say it, much closer to "rice" territory. Random Tech is a far cry from Rice, but the stock cats are MUCh deeper sounding than RT, as a result of their larger diameter and a resonator effect.

 

[Skip White]

I say ditch the sec. cat's leave the primary's alone. Or go catless all the way. Trying to weld in the RT's is not so easy. I do like the primary pipe, and factory flex joint conected to it. This is really hard to subsitute. Danniel is correct about the Rt's. They are just to small to flow as well as the oem primary, at least I think so. The length of the substrate doe's also matter. If your going catless all the way, I strongly recommend the Mopar off road setup. They are the only ones that have there system going all the way to the collector, and they do have a flex joint also, if memory serves me. That is what I'd run if I were going completly catless.

 

[Skip White]

Hay Daniel, since you have both cats out, have you measured how deep the honycomb block is in each cat, and how is the veiw looking through them. Is one more obscured than the other.

 

[Viper Specialty]

SKIP- The Primaries are OK, but the problem with them is 3-fold. The Flex pipe is a restriction, as it does go down to 2.5" internally, and there is no way to change it. From the 3" collector, this is a bottlekneck. Second, the "out" end of the primary is actually a shell within a shell, with some insulation between. In order to make it a 3" out, you will have to cut through both shells- and it is a NIGHTMARE to get them lined back up again, and then an even bigger nightmare to seal them back together- and all that is assuming you didnt damage the substrate when it was moving around. Third, the Primary cat's cell structure is much more restrictive than the secondaries.

Here are the measurements:

OEM Primary- 9cm long, 13cm diameter (the housing w/insulation makes it APPEAR larger than the secondary- it is not)
(Face Area= 132.75 cm^2, Volume= 1194.75 cm^3)
OEM Secondary- 10cm long, 13cm diameter
(Face Area= 132.75 cm^2, Volume= 1327.5 cm^3)
RT- 9cm long, 10cm diameter
(Face Area= 78.55 cm^2, Volume= 706.95 cm^3)


The RT and secondary can be directly compared, but the Primary cannot. The Primary is a Ceramic substrate with a much tighter cell structure. By looking though them, hands down the secondary can flow much more than the primary. As an example, when looking though the primary at a flashlight, all you can see is dim light. When doing the same with an RT or OEM secondary, you can see the flashlight itself, features and all.

 

[Viper Specialty]

Very interesting. I'm glad I kept all of my old exhaust stuff after installing the Corsa Track system.

I have no idea which cats are which. Could you please post pictures of the stock ceramic and metal subtrate cats and identify which part is which?

In the top picture, the larger Cat is the OEM secondary, which would normally be located in the Side Sills of an SRT-10. The smaller cat next to it is a Random Tech cat, which was cut out of the pipe the OEM is now welded into in the picture. Basically, in this setup, the secondary cats located in the sills are moved up to the area in front of your feet, and all of the 2.5" pipe is replaced by 3". there is no longer a second cat in the sills. The OEM primary is not shown in the pictures- but it does not look the same as either of those.

 

[ILLSMOQ]

So Daniel, how has the secondary cat worked out for you?

 

[Viper Specialty]

Wow...old post!

No issues at all.

 

[ILLSMOQ]

Yeah haha. I was comparing a set of Random Techs to a set of stock cats I had laying around and remembered reading that the stockers were high flow.

Did some thread searching and found this post.

Figured I'd resurrect your thread and find out how they worked out for you.

Good stuff Daniel.

btw - Summit Racing has mandrel bends available in many sizes and shapes...not quite as pretty as the stainless stuff but works just as well and won't crack as easily.

 

[Racer Robbie]

This is a great mod Dan. I noticed that the Hi Flow RT cats were smaller also. I have over 8000 miles on them with no problems at all and no rotton egg smell. You should start selling this setup and charge a core charge so you get the OEM secondary cat back to use on the next set. I would be interested in offering them for sale if the price was compairable to the RT's.

Robbie

 

[zorroespanol]

Catless doesnt stink like rotten eggs, but it BURNS your nose and eyes sometimes, especially in the SRT. Cross-winds/backwinds in slow traffic can make it unbearable quite easily.

Also, going catless has its other downfalls, such as a completely different tone. the exhaust pitch is much higher and raspier without them... dare I say it, much closer to "rice" territory. Random Tech is a far cry from Rice, but the stock cats are MUCh deeper sounding than RT, as a result of their larger diameter and a resonator effect.

Daniel, I consider you THE MOST knowledgeable guy on this board, but this time you are ******* out of the bowl!!

I am cat-less (04 SRT), and never smelled rotten eggs, never been unbearable in cross winds. In fact, never ever smelled the exhaust!!! and I am in Miami, my car is 80% of time top-down. and many times stop-go traffic.

Also, the exuast note depends on the mufflers. I have anything but ricey, high pitch noise. If you have been reading my other posts, my problem in fact is a deep, drone that is anything but high-pitch!. When I first did my exhaust I thought in fact that it wasn't loud enough.

again, the mufflers make the differece in sound, and if your car is running right there shouldn' be foul smell in the exhaust.

my .02

 

[Viper Specialty]

Catless doesnt stink like rotten eggs, but it BURNS your nose and eyes sometimes, especially in the SRT. Cross-winds/backwinds in slow traffic can make it unbearable quite easily.

Also, going catless has its other downfalls, such as a completely different tone. the exhaust pitch is much higher and raspier without them... dare I say it, much closer to "rice" territory. Random Tech is a far cry from Rice, but the stock cats are MUCh deeper sounding than RT, as a result of their larger diameter and a resonator effect.

Daniel, I consider you THE MOST knowledgeable guy on this board, but this time you are ******* out of the bowl!!

I am cat-less (04 SRT), and never smelled rotten eggs, never been unbearable in cross winds. In fact, never ever smelled the exhaust!!! and I am in Miami, my car is 80% of time top-down. and many times stop-go traffic.

Also, the exuast note depends on the mufflers. I have anything but ricey, high pitch noise. If you have been reading my other posts, my problem in fact is a deep, drone that is anything but high-pitch!. When I first did my exhaust I thought in fact that it wasn't loud enough.

again, the mufflers make the differece in sound, and if your car is running right there shouldn' be foul smell in the exhaust.

my .02

Hello,

If you re-read my post, you will see that I was informing someone that catless does NOT smell like rotten eggs. However, Catless will have an unburned fuel type odor, which can bother many people. I have compared RT cats to catless, same car, heads up- trust me, there is a HUGE difference. As soon as I went catless, I also got complaints from fellow Viper drivers who happened to be unlucky enough to be sitting next to my car while running for extended periods. I personally also felt the effects of it, especially when leaning down near the exhaust or sitting in traffic next to walls/barriers or close to other cars- I wear contact lenses, and the fumes seemed to "stick" on the lenses for a short time. Not sure if this would be better or worse without the lenses. I have never had these occurances with the cats installed- any type of them.

Secondly, as far as exhaust tone, I challenge you to drive an SRT that has the same catback as you, same headers, but WITH Cats. I GAURANTEE it will sound different. From my own personal car, catless sounds very different that with RT Cats, and RT Cats sound very different that my setup as well.

PS- You also have Vortex cones in your exhaust- they change the game a LOT. I have them in my setup too, and they definitely changed the tone. Mine were installed later however, so I know what the setup sounds like in every variation. That heated cone may also burn off SOME of the unburnt fuel too, which may also be helping the smell.

 

[zorroespanol]

I also installed the cones a few months after the mufflers. There was a noticeable difference in sound, but not much. And there was no change in smell before or after the cones.

I do agree with you however that a catless car is way louder than one with cats... unbearable for most people, especially with the exhaust a couple of feet away from our heads!!!

I asked this somewhere but I ask you now: Do you think if I ran a 2" pipe from the exit of each muffler to the other, I would notice a sound decrease?? My theory is the sound pulses will cancel each other out... I have no experience with X-over pipes so I am just theorizing...

P.D. great work with those cats!

 

[Viper Specialty]

I also installed the cones a few months after the mufflers. There was a noticeable difference in sound, but not much. And there was no change in smell before or after the cones.

I do agree with you however that a catless car is way louder than one with cats... unbearable for most people, especially with the exhaust a couple of feet away from our heads!!!

I asked this somewhere but I ask you now: Do you think if I ran a 2" pipe from the exit of each muffler to the other, I would notice a sound decrease?? My theory is the sound pulses will cancel each other out... I have no experience with X-over pipes so I am just theorizing...

P.D. great work with those cats!

Hmm... thats a good question. I think there will be SOME change, but whether it is enough to justify the work, probably not. Most crossovers on the market bring the piping into very close proximity before they actually cross.

 

[ILLSMOQ]

Zorro - I doubt you would even notice a difference at all.

 

[Racer Robbie]

Final GTS

To go back to my question: "This is a great mod Dan. I noticed that the Hi Flow RT cats were smaller also. I have over 8000 miles on them with no problems at all and no rotton egg smell. You should start selling this setup and charge a core charge so you get the OEM secondary cat back to use on the next set. I would be interested in offering them for sale if the price was compairable to the RT's."

Robbie

 

[Viper Specialty]

Final GTS

To go back to my question: "This is a great mod Dan. I noticed that the Hi Flow RT cats were smaller also. I have over 8000 miles on them with no problems at all and no rotton egg smell. You should start selling this setup and charge a core charge so you get the OEM secondary cat back to use on the next set. I would be interested in offering them for sale if the price was compairable to the RT's."

Robbie

I would be more than willing to make them if I was sent the raw materials... just need a set of RT cats, OEM front sections, and (optional) Vortex Cones.

 

[Racer Robbie]

well I have the oem front sections but no used rt cats