new cat and cutting out the resonator

Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's, Olds 98 91-96, Buick Lesabres and Park Avenue 91-96. Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.
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spoiledred94
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new cat and cutting out the resonator

Post by spoiledred94 »

I bought a universal fit (pn:91006) magnaflow cat for my 94 se (L27). I was hoping that when I cut the old cat out that I could also drop the rear most cut to behind the oem resonator that runs straight back to the muffler. I have already replaced the oem muffler with a thrush resonator.

I was reading a post by 2000silverbullet and it was mentioned that cutting out the cat would drop low end torque pretty badly.

So, my setup would be something like this GM stock exhaust from the block (no better exhaust for my L27 available) into the magnaflow cat and then straight back to the Thrush resonator and then out. I just want to know if I'd be better off with or without the oem resonator.

:bstooges:
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Re: new cat and cutting out the resonator

Post by alexcoqui »

from what Ive read here in the forum, the only diffrence would be on the sound. I took mine out & the sound dosnt bother me, but Ive heard some peolple here say that they think it sounds ricey.
I would sujest that if you remove it, dont throw it away just in case you dont like the sound.
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Re: new cat and cutting out the resonator

Post by bonnevillain »

i say leave the resonator in. like alex mentioned, it won't help power to remove it and it will sound much more raspy / ricey

but again, its all about opinion
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Re: new cat and cutting out the resonator

Post by spoiledred94 »

I went ahead with it this afternoon. Had them drop the oem resonator and replace the cat. Sounds a lot better, but I am still unsure of any performance improvements. The traffic in PDX today was hard and thick so I couldn't try a WOT run Maybe tomorrow.

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Re: new cat and cutting out the resonator

Post by spoiledred94 »

I don't know anything about top end right now, and the low seems to have been reduced some. It felt like a slower maybe even more hesitant to accelerate thing. The top end may be there if I get the nerve tonight.
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Re: new cat and cutting out the resonator

Post by spoiledred94 »

Well this is what it feels like: Since I redid the exhaust the car seemed slow to respond from a stop for a day or two, but has gotten more responsive and quicker from a stop. How long does it take my PCM to set itself after a change in the system? I only went WOT for a thousand yards and it seems faster if not quicker. How can a I get a accurate record of my 1/4 mi time w/o paying $100 to the local public drag strip?
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Re: new cat and cutting out the resonator

Post by olblueeyesbonne »

bonnevillain wrote: it won't help power to remove it and it will sound much more raspy / ricey
Actually, it will help with power, but not much. The internal diameter of the 94-99 resonators was like 2" or less.
I am not saying delete the resonator altogether, but rather, get a high flow unit in as that will prevent an annoying drone.
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Re: new cat and cutting out the resonator

Post by willwren »

$100 at the dragstrip?

Find another dragstrip. It's usually only 35 bucks at Woodburn or PIR.

The PCM dosn't have a whole lot to learn from an exhaust change that far back in the system. Most of what you're feeling in gains is probably strictly in your head. Any time you open the exhaust up too much, you will lose low-end torque, and you will not get it back over time.
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Re: new cat and cutting out the resonator

Post by spoiledred94 »

Willwren, I made an impatient blunder. Will you recommend a resonator for use in my car? It would be the only thing in my exhaust beside the magnaflow high flow cat. :)
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Note if you pull the injectors to obserbe fuel delivery...make sure you leave the plugs in and disconnect the ign. Believe me
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Re: new cat and cutting out the resonator

Post by alexcoqui »

Again, if you dont like the sound, then add a resonator. but dont think that it will give you back lost power. it wont.
If you installed to big of a cat, then that is your problem.
Like Will mentioned earlier, sometimes our head play games with us. Like yesterday I changed the oil & I can swear that the car feels more responsive, but in reality :roll:
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Re: new cat and cutting out the resonator

Post by spoiledred94 »

I've asked around about what to replace my oem resonator with. Right now I have a magnaflow hi-flow CAT, and a thrush 22" cherry bomb at the tail end. I removed the OEM 36"+ resonator that was between the cat and the rear end resonator. this made the car lose its low end torque due to the decreased back pressure. I'd like to know if the way it is now would work well with nitrous kit or should I go ahead and replace the oem resonator with another resonator, perhaps with a smaller in/out diameter?
2001 Bonneville SSEi. 1598xx mi.
great car. Wrecked

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Burnt Bonny.

Note if you pull the injectors to obserbe fuel delivery...make sure you leave the plugs in and disconnect the ign. Believe me
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