catalytic converter delete?

ok soooooooooo........ i gotta ISSUe.......... ummm remember my sweeet exhaust with NOOOOOOO mufflers...... well remember the MOM APPROVED MUFFLER ADd. yahhhhh well i have two flowmaster mufflers and still have the resonator and car welllllllllllllllllll............ what would happen if i removed the cat and replaced it with a pipe?......... yah or nah???????? would it be ALOT louder or just a little grumblier?????

do you have inspections in your state? visual or emissions?

Removing the cat will probably not yield big gains since you'll still have the resonator, which is one of the biggest restrictions in the exhaust.

I removed my cat and put headers on, left the resonator and stock mufflers on. It definitely made a difference, I'd guess it added 15 hp or so. Deleting the cat made almost no increase in exhaust level. It sounds lower, but not much louder. Here's a clip: http://www.hometown.aol.com/aasearles/exhaust.wav

of course, because of the headers.

i just want it to be a LITTLE bit deeper and louder and then maybe knock off a few patches of KR............. idk.........

98riviera98 wrote:

i just want it to be a LITTLE bit deeper and louder and then maybe knock off a few patches of KR............. idk.........

It won't knock off patches of KR. It may help a little but not much. I'd get rid of the resonator thats pretty restrictive. It will make it sound louder and deeper but you WILL get a drone on the highway.

no resonator with flowmasters will most likely not be pleasant, but everyone has different tastes.

im thinking about deleting my cat from my 95 rivi sc, but my cousin sez that in doing so, the computer will throw up all kinds of codes! is this true? and if it does, will the car refuse to run? or run really poorly? i deleted a cat from a 88 acura legend coupe,and lost some low end torque a few years before i got my rivi, but at the top she really ran fine! up to 140 mph. what im afraid of is the computer just quiting on me because of the delete on the rivi..........

you will most likely get a code but fellow member "MR. RIVERA" only gets a code Once in a great while with his delete....... your best bet would be a O2 simulator

95's had the rear O2 sensor? IIRC all GM's in 95 were OBD1.5 and didn't have a second one.

I deleted my cat. Because your car is supercharged, you won't notice a loss in torque. If you set off a code, it will illuminate the SES light, but won't cause your car to run badly. But like BillBoost said, the OBDI doesn't have a 2nd O2 sensor, so might not even throw the code.

And you won't run to 140 mph in the Riv because the PCM is limited to 108.

All Rivs limited at 108? Interesting tidbit.. you may find some are at 128mph. This would be based on the tires the car shipped with and listed on the sticker in the drivers door jamb.

I've seen SC'd B'villes with both 108mph and 128mph limiters. Talk about pissing off a guy... stock for stock and one stops at 108mph..lol

From what I hear,you may get a popping sound when you let off the throttle from unburned fuel if you delete the cat.

If there's a Riv that isn't limited to 108 mph, it would be a '95, but I haven't heard of one that wasn't. What rating were the tires on '95s? My '98 came with the "optional" Michelin tires, which literally broke apart at high speed with less than 40k miles.

Usually, the popping is only audible when you let off at high revs (engine braking while manually holding 1st, 2nd, or 3rd at very high speeds). If you let the trans do the shifting automatically, it will upshift before any popping occurs. I don't think the pops are dangerous, and they sound really cool, imo. Have never watched for it, but at night there's a chance that you could see fire from behind. THAT would be awesome!

Sounds like the rev limiter or fuel cutoff?

thxfor the info guys ! im goint to cut it off right away! sucks about the highway drone that comes with takining out the resonator too. but on my old legend i just turned up the radio, and everything was fine!

Limiter is fuel cutoff.

Removing the cat will not cause much drone if you leave the resonator in. I still have my res along with stock pipes/mufflers. The exhaust wasn't too bad on these cars, imo. Best improvements happen upstream, closer to the manifolds.

98riviera98 wrote:

you will most likely get a code but fellow member "MR. RIVERA" only gets a code Once in a great while with his delete....... your best bet would be a O2 simulator

this is true. and i dont know why my car is like that. i have a rear sensor still pluged in and a 3" straight pipe in place of the cat.

i have no drone with my 3" DP and cat delete. i do get some popping when revving down in 1st gear, most noticeable in parking garages going down hill

but like Aaron said, it kinda sounds cool...holding first, decelerating from like 40mph, blower whining like crazy, fuel being tossed into the engine for the fun of it, and the exhaust trying to keep up

oh, and dont take out the resonator. you will only see minimal power gains, and it will sound like shit! i have a friend that had a 95' and no cat/res and it was awful sounding.

quote: "this is true. read and i dont know why my car is like that. i have a rear sensor still pluged in and a 3" straight pipe in place of the cat."

Maybe rear O2 sensor is bad? Mine used to set off about every 3 days once I ripped the cat out.

As for the resonator, we're not really sure how much gain you get from removing it. Surely it offers some advantage, but is it worth doing? Personally, I think the more flow mods you have, the bigger the benefit of a res delete. I have solid evidence that my exhaust system is compromised, but not until about 5900 RPM; I never use the band that high, even when racing. If you do nothing else to the engine except remove the res, I think all you'll get is a lot of noise.

mine only sets off on long trips at 70mph. if i go faster it wont set, and i can drive in the city all year and never set the code, not even a pending code.

it is P0420 btw.

Mine always set off at idle. Same code, P0420.

lots of cool info there guys! thanks again! but have any of u had problems passing smog ,along with the cat delete? i live in nevada and i dont know if a cat delete will allow me to pass. but i just got it smogged last week,so im cool for a year. i suppose if paranoia sets in at the next scheduled smog test i can just instal a temporary cat just to pass......

I ran 3in straight pipe with no res or cat and popped in an O2 sim. no problem at all. (97) Unless they actually look under your car (they definitely don't in IL), emissions is no problem with a simulator.
It never pops unless I'm playing. It smells exactly the same as with the cat (although my cat wasn't in top shape or anything)

unless you're re-piping it all, I'd say just keep the resonator.

I noticed a different odor with the cat removed. Smells like it's rich. My '70 Olds with no cat smells the same.

Some states hook up an exhaust probe to actually measure emissions, right? If so, you'd fail for sure. But if you take a car with no cat to any emissions inspection, and they pass you, that's not saying much for the inspection procedure. I'd think the first thing they'd do is look under the car.

if i was going to remove my catalytic convertor how would i go about doing so and what are the pros and cons for doing so? thanks for you help