Hi-flow cats and stock exhaust: Does that make any sense?

[Parisianviper]

Hello everybody, this is my first post, please don't hit too hard...

Because of highly restrictive european noise regulations, I would like to keep the stock muffler and resonators on my 01 RT/10 ( The other reason is that I mainly drive my car in the narrow streets of Paris).
I read that stock cats are responsible for a lot of backpressure and heat, hence my question: Will switching to Hi-flow cats ( oval Roes or Random tech) on an otherwise stock exhaust, provide any extra power, reduce sidesill heat? Can it be dangerous for the stock rear muffler since it will handle more flow?
Will the noise be only slightly modified?

Thanks for your input .

Eric.

 

[GTS Bruce]

High flows will help.If they don't sniff your car get rid of them completely and use sims.The sills will be then only warm to the touch.I have headers to 3" collector,3" stainless to 3 " Corsa and no cats.On the gas its outrageous.However off the gas or at light pedal you barely notice the difference between stock.Never had a problem even passing cops at low throttle openings.If they have a listening station you must go to and rev it then you are of course screwed.HIgh flows will not make much diff in sound volume but should be cooler.There's nothing worse than a great looking car that sounds like a delivery truck.A good sounding cat back with high flows won't increase sound levels very much either. GTS Bruce

 

[Parisianviper]

Hi Bruce,

I forgot to mention that I would like the car to pass emission testing, that is why I would like to keep some kind of catalysor on the car. But your answer tells me it's feasible, I plan on using Roe's insulation material to really keep the heat level down. I can start with hi-flows first, then switch to a cat-back if the sound is not loud enough.
The stock cats being welded on the header side, how do you remove them?
With a good old saw?

 

[my viper]

Hello everybody, this is my first post, please don't hit too hard...

We only hit the gas hard. Relax, you are in good hands

 

[angleiron]

Actually...Sean Roe told me that he felt that doing the hi-flow cats with the stock exhaust was fine, and that the sound was actually nice in that combination. Call Sean...ask him.

 

[CitySnake]

Hello everybody, this is my first post, please don't hit too hard...

Because of highly restrictive european noise regulations, I would like to keep the stock muffler and resonators on my 01 RT/10 ( The other reason is that I mainly drive my car in the narrow streets of Paris).
I read that stock cats are responsible for a lot of backpressure and heat, hence my question: Will switching to Hi-flow cats ( oval Roes or Random tech) on an otherwise stock exhaust, provide any extra power, reduce sidesill heat? Can it be dangerous for the stock rear muffler since it will handle more flow?
Will the noise be only slightly modified?

Thanks for your input .

Eric.

Eric:

I had the set-up that you are considering (on an '01) for 25,000 miles (stock factory header, Roe Oval HF cats, stock catback exhaust system). The sole exception was Corsa SS tips which are irrelevant regarding your concern.

There is a very slight increase in power as a result of swapping out the OE cats. There is a noticeable decrease in sidesill heat. There's no danger to the mufflers and resonators (25,000 miles should be sufficient to prove that). There is a slight increase in exhaust noise. Very slight. If I had to guess I'd say it was +-5db. There is a noticeable increase in downshift popping and "burble".

No problems with emissions testing.

I have recently removed the resonators (leaving the mufflers) for a bit more overall exhaust sound.

PM me if you have any other questions.

 

[Parisianviper]

Thanks angleiron I will do that.
CitySnake, I can see you drive in the big apple and you probably have the same concerns I have about the car being too loud in city traffic. Your answer confirmed that it's safe for the car and that you can still gain from that mod.
How hard is it to remove the Cat from the header side?

 

[troyrt10]

Eric,

I have a 96 GTS. I deleted my rear muffler and the car sounded a a little meaner(louder) I wasn't satisfied so I cut off my Cats and repalced them with straight pipe. The sound was awesome at Idle and Acceleration, and the heat from the sidesills was pretty much gone!
However!
The gas smell was BAD and crusing on the interstate was very loud. Hard to carry on conversations with my wife(who also hated the smell) I decided to try Sean Roe's HF Cats. The sound is AWESOME! It's a lower rumble. Much of the higher sound waves are muffled and the gas smell is non-existant. The heat from the sidesills are also reduced(but still hot).
I think that the Viper runs better with High Flow Cats and the rear muffler delete. I think I am getting around a 20hp increase due to the lack of Cats and rear muffler.

Also, the HF Cats from Roe weigh about 7 pounds compared to about 20 pounds from the stock Cats. The HF's are also about 1/3 the size of the stock Cats.
I hope this is helpful info to you. I really love the way my Viper sounds and runs now.
Troy

 

[Mr Hemi Head]

I have been to Paris several times, your Viper must attract allot of attention.
The loudest vehicle I encountered was an occasional Harley Davidson Motorcycle, the rest were 4 cylinder micro cars and they were very quiet, compared to the SUVs in the US. LOL

The streets are narrow, air conditioned buildings uncommon so windows are open during the summer and folks like to sit outdoors in front of cafes.

I had Roe Cats and IMHO they are not for your car in Paris.
BUT if you insist I have installed these with the Roe cats:

http://www.secureperformanceorder.com/dynatechstore/getproduct.cfm?CategoryID=28&ClassID=266&SubclassID=1278&ProductID=5339

and they did reduce the noise at low RPMs. Rick

 

[Parisianviper]

Thanks Troyrt10, I will defintely go that way, keeping the rear muffler for now and upgrade to a cat back system after experimenting.

Mr Hemihead, my car attracts a LOT of attention in Paris, and that was the point!!! Otherwise I would have bought a Porsche witch are pretty common around here. Since I drive this car, people have stopped honking at me if i drive too slow (that happens...), they just ****** me, it's funny.....
Thanks for the link. Do you get any loss in performance with that product?

 

[Parisianviper]

What do you think of these adjustable mufflers:

www.powereffects.com