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Old 03-24-2003, 01:12 AM   #1
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Default catalytic convertor question

I just got through changing my muffler from the OEM to a Turbo Muffler with new dual tips and was hoping on a new sound. I was kinda disappointed when the muffler guy told me if I wanted a different sound I would have to remove my catalytic convertor. My question is would changing the catalytic convertor out for a high flowing one make any difference in the sound quality or should I have just picked a diferent muffler. I was really disappointed in my Bonnie even though I can feel a difference in the power with my new muffler I still don't have the sound I'd like to have had.
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Old 03-24-2003, 01:30 AM   #2
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When I changed to a high-flow cat, I noticed the difference in sound immediately. A bit throatier....sortof like a boat at idle on the street. You can really hear the cam if you know what I mean.
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Old 03-24-2003, 08:36 AM   #3
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I had my cat pulled completely. I can hear a HUGE difference in sound. I am also running 3" pipe as well. I probably have one of the loadest Bonnevilles of my type ever made. It seems that the most common muffler around here is the Flowmaster, but Iam using a Magnaflow which is a bit more open inside.
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Old 03-24-2003, 09:31 AM   #4
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Mine is pretty throaty too...nothing like SSEi95'* but it gets the point across.

High flow cat, 2.5" SS pipe, MagnaFlow muffler, single tip...well, custom single tip. If I were you tho, I'd get the 3"

Go cat-back all the way!! In some states/provinces its illegal to go with no cat and here in CAN, we have emissions and "Drive Clean" tests every 2 years. We gotta have em!
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Old 03-24-2003, 12:30 PM   #5
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3" isn't a good idea with an LE or SE, even most SSE'*. Without the other mods to back it up, you'll lose low-end power. The car he'* talking about has a 2.25" exhaust. Don't go more than 2.5" diameter.
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Old 03-24-2003, 05:58 PM   #6
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So, in other words, a 3" system on my 1994 SLE is going to be overkill? I am running a CAI, 180* t-stat, NGK V-power plugs, 8.8mm wires, removed maf screen from the TB, and always run 91-93 octane. Future plans include a Superchip, MSD coil packs, 3" high flow cat, 3" mandrel bent pipping, Magnaflow single 3" inlet --> and dual 2.5" outlets --> --> with (2) 2.5" inlet dual 3" outlets with resonator tips.
I just got to start driving the car Saturday, and even with the current mods I still got killed by a 1994 Grand Prix SE 3.1. Well actually, she didn't really win -I let her get a good jump before I kicked it down. She was going about 30 with a full throttle and was about a car length ahead and I was going about 15 when I kicked it down so she kept pulling on me but only for 3-4 seconds before I started reeling her in. Of course I let her "win" - just earning my self some brownie points before I went for the kill - or as it is more commonly known . Of course I couldn't take it then, but I got a rain check because I had a friend along who I didn't feel like leaving with my car while I went and "scrogged". That'll be this next weekend -
Anyhow, for right now i just have to replace the right rear control arm as it broke last night while hauling about 800lbs of friends around town "....driving fast cars, and chasing hot women!!"
Oh, and the other fast car was my cousins 1996 Buick Riviera Series II 3800 Supercharged. Pulled up next to him at the stop light with two loaded cars and we pulled even!!! I am psyched. Of course we only raced up to 45, but it was neck-and-neck the whole way. Can't wait to put the superchip, MSD coil packs, and the exhaust system in. Hopefully I'll kick his *** then. Even better when I get my dry 75 shot. Kicking it down at 30 mph with no passengers I can get it to chirp the tires.
I had a guy in a Monte Carlo ask if I had a Chevy smallblock V8 in it because of the tone of the exhaust with the cold air intake. It does sound sweet (much throatier like an exotic engine sound. It definitely sounds different than my old 1992 with the cone filter on the stock airbox hose and no catylitic convertor. Boy is good to be back in a Bonneville (the Lesabre wasn't too bad, but it'* just not a decked out Bonnie).
Anyhow just letting you know I got the car on the road (for 2 days anyhow), and it'* been a blast. More to come when I get it back and more mods done.

Stylez
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Old 03-24-2003, 07:46 PM   #7
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Quote:
Originally Posted by OLBlueEyesBonne
So, in other words, a 3" system on my 1994 SLE is going to be overkill? I am running a CAI, 180* t-stat, NGK V-power plugs, 8.8mm wires, removed maf screen from the TB, and always run 91-93 octane. Future plans include a Superchip, MSD coil packs, 3" high flow cat, 3" mandrel bent pipping, Magnaflow single 3" inlet --> and dual 2.5" outlets --> --> with (2) 2.5" inlet dual 3" outlets with resonator tips.
Unless you plan on fitting a turbo or a SC under the hood the 3" will probably won't help at all, and my even hurt your low end torque. Without getting in to college level physics, the basics are that the airflow needs to retain a certain volume and flow to run smoothly thru the pipe. If the pipe is to large the air will flow every which way and cause poor exhausting of the engine. With a turbo or a SC it adds enough volume to do the 3" and get away with it.

I personally have the 3" only because I have the SC, a few engine mods already, but primarily because of the upgared that are in progress like the 2.5 SC pulley for more boost. Besides, a 2.5" exhaust will cost a lot less than a 3" for materials.
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Old 03-24-2003, 07:53 PM   #8
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So would going with a high flow 2.5" cat and 3" piping after that be ok? Or should I just get the 2.5" high flow cat, 2.5" mandrel bent piping and get a 3"-2.5" reducer for the 3" inlet on my muffler? Any way I can get the biggest bang for the lowest buck I would definitely use. Would hate to pay for the 3" setup only to find it was a waste of money.
Thanks for the tip. Hopefully I'll have it all done (all mods on my 1994 SLE) by the time April 26th comes around. Right now since the right rear control arm broke last night I am getting SSE rear springs put in for the 1" lowering effect.
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Old 03-24-2003, 09:30 PM   #9
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Will changing to a hi flow cat make anymore horsepower?
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Old 03-25-2003, 12:07 AM   #10
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It will...a few horsepower, not much, but you may notice. It helps to do the whole exhuast. Seems you have done that already
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