Punched-out CATS...... What's it sound like???
 

Just as the title says... My car is a 1995, and when I have to get my car inspected again, they will nolonger do emissions... I am looking for something that would complement the Stebro Exhaust that I currently have... Something that will let it breathe alittle better for AutoX competition.... Something that will "Free the Ferrari within" (The sound I mean)... Anyone who has heard a 3 peice Stebro will know what I'm talking about :D:D

So I was looking at Random Technoligies CATS... They are VERY expensive.... :(:( But they flow the best of any CAT I have ever seen (if there is a better one out there, please show me!!!)

There are generic off brand CATS that "claim" to be "High-Flow".... But you know they probably are talking about an extra 5 or 10cfm or something... That sort of Ripoff is not acceptable...

Apparently CATS from a stock 1999 Mustang GT will work, and flow more than our stock ones.... But I'd prefer to stay away from "Rigging" components on the car...

CATless exhausts (from my experience) sound very RICE.... That is the last thing that I want my SVX to sound like... Can anyone comment on how Punched out Primary CATS sound??? Remember, I already have the 3 peice Stebro (no 3rd CAT)... If I punch out the two primary CATS who thinks it will sound like RICE??? Who thinks diffrent?? Who has an AUDIO clip of punched out CATS???!?!?! :):)

I punched out the converter on my civic and it sounded like crap.. If I were you I'd just leave it, not like you'll gain any noticeable power anyways, maybe like 2 hp.

I also agree to not get rid of the cats completely. One option would be to swap the "Euro Resonator" for a 2>1 center cat then gut the pre cats.

From my experiance, punching the cats makes a high pitched "Reeow" kind of noise , usually followed by a hiss.
Gutting the cats just makes a mess, but makes cooking them alot less painstaking. I recomend that you lay down some plastic to keep things clean before doing this
Hope my explanations answered some concerns

Gut the cat????
 

Hi Chris, the front cats are an integral part of the SVX exhaust design. They are accounted for in the operation of the system. Even the non catalytic models like Danny's, that can run leaded fuel, have the cat box with the ceramic brick in there, just not coated with the catalytic metals, to allow the system to work right.

If you want to remove them, it is better to replace them with pipe, if you just punch the brick out of them, you will end up with two empty chambers that will lose you some low end torque.

Harvey.;)
p.s. Do you know that Lions brewery is trying to buy Coopers, this must never happen.:(

well i can tell you that i dont have any pre cats and a 2 into 1 high flow center cat and it resonates like no other at 3000-3800 rpms. I have been told this is b/c of the lack of pre cats by many on here. So i would say if you take em out replace them with something else. Definitely wish i had done that. Never know though with the stebro it could be different

This is what the former owner of my other '92 did, and it sounds fine

Yeah, I figured that the CATS were definitly a part of the Exhaust design and that if I removed the materieal I'd loose that torque down low that gives me the advantage over a good number of WRX's on the AutoX course.... The thing is though, What to replace them with??? Straight pipes are pretty much out of the question. That changes the exhaust even more... Replacement "High-flow" CATS sound like a great idea, however they are so $$$$.... Does anyone know of a High-Flow CAT that will fit where the two primary CATS are on the SVX??? I'd prefer an all Metallic CAT (Like the Random Technoligies CATS) that flows around 400cfm and that doesn't cost an arm and a leg...


Harvey, I didn't know that coopers was up for sale!??!?! That's terrible!!! :eek::eek::eek:!!!!

I'm sitting here imagining a catalytic converter in a pot of boiling water.

Mmmmm..

meowwwwwwwwwww?:confused:

I've been through my share of header back exhaust systems on my SVX, and in my experience, removing the primary cats doesn't hurt low end power at all. I've always figured that the ceramic mesh would be detrimental to any kind of exhaust dynamics. It disperses sonic waves, and it slows exhaust velocity. Besides that, having the exhaust pipe open up at the primary cats causes a sonic reflection that would only provide a benefit at something like 7000 rpm. As I see it, that sonic energy is going to waste and would be better used if it were reflected at a point further down the exhaust line where it could cause gains in power at a useful point in the powerband.

I've heard an SVX "uncorked" before, and it is REALLY loud, but I like the sound of it, it's very mean. I don't know if you should just punch the cats out though, with the stock piping being smaller, wouldn't the diference in size hurt the flow?

It was my understanding the pre cats act as a pre-dump at high rpms to slightly diminished backpressure.
Did I get this part wrong?

Yes, no, if the cat is replaced with a pipe, it will still allow the low speed gas inertia to work ok. If the brick is removed from the cat, and the can left, it will hurt the low speed gas inert, by having the gas pressure expand too early before it has developed the inertia to clear the cylinder. Yes it would reflect the sonic wave too early.

I feel you have a negative view of a catalytic converter.:D They are not as bad as you think.:( The area of the holes in the ceramic brick is larger than the pipe, so it does not restrict the gas flow, and it doesn't affect the sonic wave, it just pases through, just like the mesh covering over your stereo speakers, on your Hi Fi.

Harvey.;)

Hi Harvey. I understand what you mean by the speaker grille analogy, but I think the cat brick does have some sound damping because the exhaust note on my car got quite a bit louder when I removed the primary cats (with no other change to the exhaust system).