What is the Resonator and the U Bent?

I’ve been reading some of the posts related to pipes, intakes and mufflers... Can someone tell me where I can get educated and get information regarding the exhaust system on a 2000 Monte Carlo SS.
 
I just installed a set of Magna Flow.  I like the sound but it could be a bit louder.  Someone told me to get rid of the Resonator and the U Bent.  I don’t know what they are or where are they located.  I can take it to a muffler shop and tell them to take the Resonator and the U Bent out and replaced it with a 2.5 straight pipe from the Cat.  I know the guy at the muffler shop will be impressed with my talk, but I am not sure of what I just said!!!
 
What is the Resonator, where is it and what does it do?  Same with the U Bent... what is that?
 
Sorry for the ignorance, but I rather ask and get educated than to remain stupid the rest of my life. 
 
MC2K
 
 


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the resonator is just like a little tiny muffler that usually goes right after the catylitic convertor and it just muffles a little more sound out on the car...quiet's in down...but not really that much..and you gain like 2 hp for getting rid of it...i know its not much..but every little bit helps...
 
and the u-bend is right before the catylitic convertor and its a piece of exhaust pipe right after the down pipe(thats 2.5") that does a little "u" like it says thats about 1.25"  major restriction on the flow of the exhaust...there's also a o2 sensor there that they will put back in with a new o2 bung in the straight peice of pipe :)
 
hopefully i didn't just confuze you more ..lol

the u-bend is after the convertor not before.

wiz is the man he has helped me with the choice of my flowmaster selection process.
 

Thank you Mr. Josh.  You have saved me from being a permanent resident of STUPID-VILLE.
 
I think I know what you are talking about.  I took some pictures of the exhaust system when they installed the Magnaflow.  I think this should be the Resonator:
 

 
And then the U-Bent should be that piece in front of the CAT where the O2 sensor connects.  Is this right?
 
MC2K
 

yep in that pic you can see the flat area of the U bend between the resonator in the pic (top closest  to the camera and the cat furthest from the camera.
 
resonators are specificly tuned to remove certain frequencies in an exhaust system.  mufflers generally remove volume resonators remove either high's or lows at a very tight range

ok ok ok cool so now i know what the hell we looking at

yup, so get rid of all that stuff in the pic, puta highflow car in from magnaflow, and a piece of straight pipe for the u-bend and the cat resonator...you'll notice a huge difference :)

A buddy of mine said that the stock CAT from the 2000 (and up) on the Monte Carlo SS is just as good as the Hi-Flow CAT from MagnaFlow and that I did not need to change it.  Also... I've been told that by changing all of my pipes to 2.5 and get rid of the U-Bent, I will loose back pressure and power.  I was just going to replace all, but maybe I should just remove the Resonator and change the pipe from the CAT, back to the Mufflers.
 
I think it would be too risky to change all the pipes and the CAT.  After all... this is my only ride and I must go to work and back home.
 
 MC2K

quote:

ORIGINAL: MC2K

A buddy of mine said that the stock CAT from the 2000 (and up) on the Monte Carlo SS is just as good as the Hi-Flow CAT from MagnaFlow and that I did not need to change it.  Also... I've been told that by changing all of my pipes to 2.5 and get rid of the U-Bent, I will loose back pressure and power.  I was just going to replace all, but maybe I should just remove the Resonator and change the pipe from the CAT, back to the Mufflers.

I think it would be too risky to change all the pipes and the CAT.  After all... this is my only ride and I must go to work and back home.

 MC2K

Does your friend drive a ricer?  You really only need to be concerned with backpressure when you're driving a 4-banger.  High torque American 6 and 8 cylinder cars like to inhale and exhale hard to make power.  The u-bend is a restriction in the exhaust flow.  Freeing that up and increasing intake volume will allow the car to breathe better.  An engine is basically an elaborate air pump.
 
Here's what stock versus aftermarket looks like:


This piece replaces the bent piece in the top-most photo.  O2 sensor is positioned off to the side instead of on top.
 
Click here to read about it.

looks a lot better

I replaced my entire exhaust from the downpipe all the way back and saw a huge difference and every thing that i have is 2.5 from the down pipe back with a high flow cat and u-bend and then Borla on back and i have no problems with it.
 
also with the cat from your car you need to remember that it has been on there for 7 years now and it is most likely as good as it once was. 

i will definitly be removing the stock u bend cause it looks disgusting

so are you saying that if you take the resonator out... replace the u bend and just put mufflers in the back it wont be to loud?

I have ripped every inch of my exhaust system out. DP, CAT, RESONATOR and stock mufflers.  I recommend flowmasters, 40 or super 40s depending on how loud u want it inside.  I have had 3 things inplace of the resonator, a cherry bomb glasspack, a red hot resonator and straight pipe.  Straight pipe is soooooo loud but soooooo nice.  I commute 60 miles a day and on the highway the red hots was the best.  My dp with cat/ubend delete is a magnaflow and after installing it, I could tell the car had more balls.

i did the u-bend delete and no resonator first...with the stock cat, noticed a difference in performance...then i did the highflow cat convertor and noticed another difference in performance as well, and my car only had 7000 miles on it @ the time i did this...so whoever told you the stock one is as good as a high flow one is a little off on that ...
 
so now i have highflow cat, no u-bend, and no resonator, and i left the rest of the exhaust the way it was....still stock mufflers..and my car is not too noisy at all...doesn't really make any noise actually...its a little louder than stock..but not much..
 
definetely a good investment if your looking for more power

ok so once i get my mufflers done and have the u bend and resonator taken out and replace with 2.5 pipe i need to go back and have the stock changed out to a highflow cat? what is the going price for the highflow cat and i need to take it to a shop to have it put on right

i have the 3400 in my monte will any exhaust sound good.

yah it should...i dont think there's a lot of sound difference in the 3.4l and the 3.8l engines

Thank you everyone for guiding me in the right direction...
 
Bigg J - That's a great photo explanation of the U-Bent.  Nothing tells it better than a picture and I appreciate that.
 
I will be taking the car to the muffler shop this week to remove the Resonator and change the pipes to 2.5 from the CAT to the Magnaflow.  I don't think I want to take the U-Bent aout now, but I will consider it after I hear the car.  Don't wnat it to be too loud!
 
I will try in taking pictures and post them later.  Again, thank you to all.
 
MC2K

the u-bend wont change any sound at all...and thats where all the power is lost...i dont think you will notice much of a difference without that being gone first

OK... Question then:  Can I replace the U-Bent with a straight pipe WITHOUT the connector for the O2?  What would be the consequenses?
 
MC2K

If the computer doesn't get signal from the O2 sensor it will probably go to a general map (reducing power) and leaving you with stock fuel delivery (eliminating any benefits of mods you have)  If you leave the O2 sensor connected, just not in the exhaust, then it will read very very incorrectly and the car will never run right.  The best option is to either 1, use the O2 sensor eliminator available on some sites, this tricks the computer into thinking the car is running properly.  Or, having the guy weld in an O2 bung.  By far it's better to have the 02 sensor connected  and placed properly in the exhaust system.  without the O2 sensor your car won't adjust for temperature, air density/altitude changes as effectively as it normally would.

you would have to leave the o2 in place, all they do is put a piece of striaght pipe in and weld an o2 bung into the pipe for the o2 sensor...very easy and quick job...
 
i defientely would not suggest getting rid of the o2 sensor

OK... Would I have to mess with the PCM?  I had planed to change it soon, but if I don't need to, I save the $$ for when I upgrade the breaks
 
MC2K