Factory Exhaust Resonator Removal and Free Flowing Alternatives

[SteelBlueZR1]

How many of you have tried keeping your stock 2.75" factory ZR1 exhaust system and just replacing the 1990-92 restrictive resonator with an aftermarket freer flowing resonator or x pipe?

Haibeck says the stock resonator is a major exhaust flow restriction costing about 20hp, due to the resonator core reducing to 1 5/8” ID.

What is the best product to replace the resonator with to maintain the low noise and no resonance I currently enjoy?

I prefer not to go to a straight pipe or crossover, but rather find a replacement resonator with straight through 2.5-3" pipes. Has anyone tried the DynoMax® Ultra Flo™ X performance stainless steel mufflers with 3-in. diameter internal X-pipe balance tubes?

I am concerned about fitment issues, so what have you tried that fits the factory pipes and doesn't drone?

[GOLDCYLON]

How many of you have tried keeping your stock 2.75" factory ZR1 exhaust system and just replacing the 1990-92 restrictive resonator with an aftermarket freer flowing resonator or x pipe?

Haibeck says the stock resonator is a major exhaust flow restriction costing about 20hp, due to the resonator core reducing to 1 5/8” ID.

What is the best product to replace the resonator with to maintain the low noise and no resonance I currently enjoy?

I prefer not to go to a straight pipe or crossover, but rather find a replacement resonator with straight through 2.5-3" pipes. Has anyone tried the DynoMax® Ultra Flo™ X performance stainless steel mufflers with 3-in. diameter internal X-pipe balance tubes?

I am concerned about fitment issues, so what have you tried that fits the factory pipes and doesn't drone?

Well you could use a Corsa resonator. The xpipe would be better flowing but you will pick up resonance

[Gunny]

AFAIK there are only 2 systems that have NO drone ... stock and Corsa ... the fitment is fine on either system. Corsa is reasonably tame until you get above 2500-2800 rpm then it is very loud (at least to me).

The early (90-92) stock systems were not only restrictive at the resonator but also at the mufflers ... can't remember the neck down at the muffs but I believe it was about 2" or less. Also, I think that only one tip flowed; the other was for appearance. The later stock systems were less restrictive and if you want to stay with a stock system it's probably easier to get one than try to mod or adapt an early model to fit your needs; otherwise you're looking at a variety of 3rd party exhaust systems. Finding the "perfect" exhaust system for all situations is a tough, perhaps impossible task ... I know since I currently have 3 systems hanging on the garage wall plus a Corsa system currently installed. Every system I have (except for the stock 90) has a certain appeal to me but also some drawbacks ... I'm looking for the happy medium which may not exist.

Do a search on this forum ... the guys in Chicago are doing some really nice things with larger systems, C6 flapper mufflers, etc. I haven't heard any of these systems yet but plan to next week at BG ... great place to hear a lot of different exhaust systems.

George

[efnfast]

I'm running a brand new OBX system, headers and exhaust. No drone. If you're coming to BG, you are welcome to come for a ride with me and listen. Maybe you can drive, maybe.

[SteelBlueZR1]

Thanks for all the feedback guys. I would love to hear the new OBX system... But I really had my heart set on finding a replacement resonator for the stock 1991 exhaust. The 1991 mufflers according to Chevy are 40% larger than the 1990's and have much less backpressure, plus I like em quiet.

[GOLDCYLON]

Thanks for all the feedback guys. I would love to hear the new OBX system... But I really had my heart set on finding a replacement resonator for the stock 1991 exhaust. The 1991 mufflers according to Chevy are 40% larger than the 1990's and have much less backpressure, plus I like em quiet.


I have a corsa resonator in my attic. If you want to get it fit at a shop to try it out. I paid $200 for it I would let it go at that plus shipping.

[mike100]

Well you could use a Corsa resonator. The xpipe would be better flowing but you will pick up resonance

stock muffs are quiet even without the factory resonator. There might be a slight bit more rumble, but rest assured that you won't feel fatigued on the highway after a long run at 70 mph.

I would easily say that my stock 90 pipes and mufflers with the magnaflow x-pipe are quieter than Corsa at pretty much every power level.

I used the magnaflow x-pipe from their x-pipe and resonator combo- just hacked off the chrome resonator can due to ground clearance concerns.

http://i29.photobucket.com/albums/c265/mschrameck/Cars/zr1_xpipe_sm.jpg

[mike100]

I bought this from Hans when I got the stock exhaust, but ended up only using the x-pipe. You could just have your exhaust guy make one, but you could also buy this pipe for $85 from Summit.

http://i249.photobucket.com/albums/gg225/hans_meyer/IMGP3039.jpg

[GOLDCYLON]

stock muffs are quiet even without the factory resonator. There might be a slight bit more rumble, but rest assured that you won't feel fatigued on the highway after a long run at 70 mph.

I would easily say that my stock 90 pipes and mufflers with the magnaflow x-pipe are quieter than Corsa at pretty much every power level.

I used the magnaflow x-pipe from their x-pipe and resonator combo- just hacked off the chrome resonator can due to ground clearance concerns.

http://i29.photobucket.com/albums/c265/mschrameck/Cars/zr1_xpipe_sm.jpg

Having all three exhaust systems I would have to disagree with that assessment. However in the end Bert can make up his own mind as it will cost him to try systems out.

[sammy]

you could also buy a 3in xpipe from summit about 80 bucks . then buy 2 dyno max super turbo mufflers 3in inlet and dual 21/2 in outlets about 150 for both hack off the zr1 tips from the stk exhaust and have a nice no drone exhaust for about 350 and it would look stk . idf you pm me your email i will send you a utube video of my car going down the drag strip with this exhaust on my 92 .

[mike100]

One thing I am sure of that if you are worried about losing the resonator due to extra dB's out, you will be horrified with many of the aftermarket systems (including the Corsas- they are just plain loud when you stand on it).
I like Sammy's idea with the 3" turbo mufflers, but I haven't been able to find any dual outlet kind that are smaller in overall length. For now (since i don't have headers) the stock mufflers make about the same power as any other pipe. My restriction is the factory manifold so I will run it the way I have it now.

At some point, I may sell my Corsa cheap (the resonator was welded previously) and the pass side flange is custom so welding may be required to install that.

[sammy]

part number WLK17674 is what i used . the case length is 13in and total length is 17.in. price is 67.45 ea.. i just love this set up . i dropped 2.5 tenths and gained 1.7 miles an hr at the drag strip over the corsa set up . and to me it was quieter also ,but had a nice sound when you put your foot to the floor .JMHO

[GOLDCYLON]

many of the aftermarket systems (including the Corsas- they are just plain loud when you stand on it).

Lol thats kind of the point mild at idle and cruise and wild at open throttle otherwise whats the point of having an aftermarket system?

[SteelBlueZR1]

I am going to speak to Dynomax and Magnaflow, both who manufacture a resonator with a built in exhaust crossover to see if there is a size that has the right dimensions and inlet center measurements to replace the stock restrictive resonators. If I find a 2.5" or 3" resonator that works I will share this with anyone else who wants to just replace their oem highly restrictive resonator, but not risk drone and noise of an X pipe.
*DynoMax® Ultra Flo™ X performance stainless steel mufflers feature 100-percent welded construction for lifelong durability. Ultra Flo™ X incorporates a 3-in.diameter X-pipe balance tube inside the muffler - promoting exhaust scavenging and equalizes flow
-or-
Magnaflow Tru X Perforated Core- PART#: 12599 with 5.75" inlet center spacing
Inlet/Outlet Size: 3in./3in.
Body Shape: 5in.x11in. Oval
Core Size: Dual 3in.
Body Length: 22in.

Any input or ideas?

[mike100]

The resonator x-pipe combo in my previous picture may or may not be like that magnaflow p/n you listed. The resonator itself merged in the center into one big glass pack of sorts. I'm not sure why they sell it with the x ahead of it, but I had heard that it is capable of supporting a fairly high rwhp (400 and below). I did not use it because it was fairly large and would have been the lowest part on the undercarriage.

[Gunny]

I tried the 3" dynomax x-pipe resonator and it was a tighter fit than I wanted so I abandoned that idea ... whatever you decide on, be sure to carefully check your measurements for fitment.

Have you looked at the dynomax vt mufflers (internal flapper)? The claim is "absolutely no drone" while retaining all the performance characteristics ... sounds too good to be true but I haven't heard them yet. Might be worth looking at ... just a thought.

[tomtom72]

:o just a fwiw I didn't really have the $$ to spend on a Corsa system. So I looked around and found these guys:
http://www.classicchambered.com/classic/products.html

I was going to buy two of these and cut out the OE 90 resonator and splice two of these in it's place and keep the rest of the OE exhaust on my 90. I don't know how loud these are, but I was thinking these parts reminded me of my factory side pipe mufflers on my 72 LT-1. No restriction, or not much going on with these, and I figured going thru the stock mufflers the noise should be kept to a tolerable level. Don't know if this helps you out or hinders the resolution of your search for flow and no noise.:o

:cheers:
Tom

[Paul Workman]

I bought this from Hans when I got the stock exhaust, but ended up only using the x-pipe. You could just have your exhaust guy make one, but you could also buy this pipe for $85 from Summit.

http://i249.photobucket.com/albums/gg225/hans_meyer/IMGP3039.jpg

Ah HA!! So THAT's where my MF system ended up!

I bought that 3" MF system, thinking it was as advertised. But, I discovered several neck points and the resonator is a single pipe, making the sharp bends in the X pipe section redundant and resitrictive (the pipes are NOT 3" in diameter, in and out of the X section...grrrrrrr. Hans wanted to try it, so I sold the resonator and X pipe sections to him (the muffs are on my car still...for now)).

To the OP: Dominic used a MF system with success, up to the point of porting his heads. The system proved too restrictive; impeding performance after installing ported heads and re-ground cams. But, as I recall it had no resonance, and it sounded rich and deep. (Corsa sounds a bit "tinny" to me and others. Sound is a subjective thing, but resonance is prolly universally disliked.)


P.

[SteelBlueZR1]

So, I decided to resolve the restrictive 1991 exhaust resonator issue on my ZR1 by purchasing an LT4 resonator, which does not have the restrictive 1 5/8 inlet and appears to be very close to 2 3/4" straight thru. Bought this piece from "Jeff" here on our forum and am looking to have installed by Maryland exhaust shop.

Does anyone have a recommendation for a Baltimore County/Maryland custom exhaust shop who can fabricate 2 3/4" pipes to join the resonator with the existing exhaust?

[secondchance]

I'm running a brand new OBX system, headers and exhaust. No drone. If you're coming to BG, you are welcome to come for a ride with me and listen. Maybe you can drive, maybe.

Agree 100%. I am also running OBX headers and exhaust - completely happy w/ the result.

Bert - if you want you can try my car next time we meet. Any custom conversion you do removing resonator or switching to other resonators will cost at least $100-200. OBX exhaust can be had for $350.
One more thing. Factory exhaust is 2.75" system. However, depending on the year 2.75" pipe reduces by 1/2" or so at transitions to resonators and mufflers - not a true 2.75" system.

[secondchance]

Sorry Bert. Didn't realize you already bought LT4 setup.
Offer to have you drive my car still stands.

[SteelBlueZR1]

Hi Secondchance, Thanks for the cool offer to drive your Z and decide if I will be happy with the OBX vs. modding the stock exhaust. I will definately take you up on this at our next Wazoo work day. I'll hold off on installing the LT4 resonator till I hear your new exhaust. My original goal was to make the exhaust appear original and unmolested, yet free up the 10 hp lost thru the 1 5/8" 90-91 resonator restrictions.
I do really like the OBX, especially for $349'ish + shipping on e-bay, but I worry my lovely wife will hate the beautiful noise and never ride along with me.

[zrwhat]

Bert,

Recently had a shop in Glen Burnie Maryland do some custom work on my ZR-1 exhaust, they made hook ups for my slip fit headers and fitted a 3" crossover going back into 3" B&B mufflers deleting the resonator.

They did an excellent job and I'm picky as hell about others work.

Name of the place is: Mandrel Bending Solutions, they are on Mountain Rd in Glen Burnie.

Gibby

[Tyler Townsley]

I replaced my resonators with a 36 in long 3 in version of these:
http://www.classicchambered.com/
It cut the volume down quite a bit but I also have xpipe with headers and B&B muflers so it is still somewhat noisy.

Tyler

[mike100]

I replaced my resonators with a 36 in long 3 in version of these:
http://www.classicchambered.com/
It cut the volume down quite a bit but I also have xpipe with headers and B&B muflers so it is still somewhat noisy.

Tyler

I actually thought about those using an H-pipe. If i go headers it might still happen as I think it is a good way to go if one needs to keep the dB's down.

[sammy]

mike .i had an h pipe set up before i got the b and b set up from you . i later switched the the b and b head pipes and x pipe to my set up and found that the exhaust note smoothed out and got alot quieter at cruise with the x pipe

[efnfast]

Hi Secondchance, Thanks for the cool offer to drive your Z and decide if I will be happy with the OBX vs. modding the stock exhaust. I will definately take you up on this at our next Wazoo work day. I'll hold off on installing the LT4 resonator till I hear your new exhaust. My original goal was to make the exhaust appear original and unmolested, yet free up the 10 hp lost thru the 1 5/8" 90-91 resonator restrictions.
I do really like the OBX, especially for $349'ish + shipping on e-bay, but I worry my lovely wife will hate the beautiful noise and never ride along with me.
Bert, I installed the OBX headers and exhaust. My lovely wife and I drove it to BG this year. She didn't mind the beautiful noise at all.
Steve:proud:

[secondchance]

Bert, I installed the OBX headers and exhaust. My lovely wife and I drove it to BG this year. She didn't mind the beautiful noise at all.
Steve:proud:

OBX headers/exhaust, to my ears, certainly sounds healthy but not overly loud.

[Bob Eyres]

Here's a dyno proven alternative that you may have seen, but if not, it's a good read:

http://www.zr1netregistry.com/flowmaster.htm

uses mostly stock parts, and the power increase is phenomenal.
Thanks to "The Hibster".

BTW, that's a beautiful "Steel Blue" ZR-1. What a terrific color for a ZR-1.

[SteelBlueZR1]

Thanks everyone for all your feedback. It looks like I am going to go ahead and get the OBX exhaust system. I drove Yun's car and loved the V8 rumble under acceleration, 0 drone, and quiet cruising... Thanks Yun!
So, I now have an LT4 Resonator in good condition, looking for a home. It is much less restrictive than the 90-91 resonator... The LT4 resonator pipes are at least 2.5" straight thru. PM me if you are interested; I will post pictures. Will sell for $60+ shipping.