Corsa Resonator in Chicago?

[WARP TEN]

Anyone around Chicago have a leftover Corsa resonator? My new '95 just came back from Marc's after maintenance servicing, gears, Corsa install etc. and I realize that I need to modify the Corsa resonator to resolve one noise issue. I had done this on my 93 and it improved the sound. So I was hoping to either find an inexpensive leftover resonator or one that I could borrow, get modified, swap with mine and return. Either way works. Thanks--Bob

[ZZZZZR1]

Anyone around Chicago have a leftover Corsa resonator? My new '95 just came back from Marc's after maintenance servicing, gears, Corsa install etc. and I realize that I need to modify the Corsa resonator to resolve one noise issue. I had done this on my 93 and it improved the sound. So I was hoping to either find an inexpensive leftover resonator or one that I could borrow, get modified, swap with mine and return. Either way works. Thanks--Bob

Bob,

Check with Paul Workman (in your area)... He had a set made that looked identical to what you did on your old car and it's VERY reasonably priced!

I'll look for the post he did on it years ago. (probably 3 years ago) Geat modification!

How is the "new" ZR-1??? You installed 4:10 gears?

:cheers:

David

[WARP TEN]

Bob,

Check with Paul Workman (in your area)... He had a set made that looked identical to what you did on your old car and it's VERY reasonably priced!

I'll look for the post he did on it years ago. (probably 3 years ago) Geat modification!

How is the "new" ZR-1??? You installed 4:10 gears?

:cheers:

David

Thanks David-- I will check with Paul. Since you are from Maryland, you must have seen the mod I did on my old system. The problem I have with the Corsa is that under load at 2,500 rpm I hear a loud, annoying “fluttering” sound that I have described in the past as hearing individual cylinders firing, with the pulses reinforcing each other. Not the normal resonance at 1.800 and 3,400 that the Corsa handles well. Last time (probably a dozen years ago) on my 93 I improved this by cutting out a portion of the pipes where the H pipe is and behind the resonator and boxing them with stainless panels welded in. So I thought I would try it again.
The “new” ZR-1 is great. Seems to have lived in a dry climate all its life (20k miles). Marc found no evidence of any prior damage which bears out the clean Car Fax. I had Marc put in 4:10s, a Hurst shifter (he still has a couple left), a chip and installed the used Corsa I got from CorvetteGeorge. He also did lots of overdue maintenance, like oil, serp belt, clutch hydraulics, brake fluid, coolant, new hatch gaskets and struts, etc. It should be fine for a long time. The only thing it really still needs is engine refinishing, although I do have lust I my heart for headers and top end porting.... --Bob

[scottfab]

.................. The problem I have with the Corsa is that under load at 2,500 rpm I hear a loud, annoying “fluttering” sound that I have described in the past as hearing individual cylinders firing, with the pulses reinforcing each other. ..........

See now I'm going to be listening for this as soon as this T-storm rolls through. I can't say I've ever heard it. But then I don't spend much time below 3k ;)
I've always had an ever so slight peak resonance at 3.1-3.2k

[-=Jeff=-]

Last time (probably a dozen years ago) on my 93 I improved this by cutting out a portion of the pipes where the H pipe is and behind the resonator and boxing them with stainless panels welded in. So I thought I would try it again.

SO did you make the H bigger or block it off? I cannot seem to get my head wrapped around the mod you did

[WARP TEN]

SO did you make the H bigger or block it off? I cannot seem to get my head wrapped around the mod you did

Hi Jeff--
The Corsa does a great job eliminating the common LT-5 resonance or drone under load at 1,800 and 3,400 rpms. What I am hearing is different. It sounds like individual cylinders firing or as I described it a fluttering sound under light/moderate load at about 2,500 rpm. I think certain firing pulses just reenforced themselves at that speed, creating a type of resonance. What I was trying to do was to get the pulses from each bank of cylinders to mix more to smooth out the sounds.
I regret that I no longer seem to have any pictures of the modifications I did on my '93, but I will try to explain them. I first cut out sections around the H pipe about 3”-4” long on the inside of the pipes entering the resonator and removed the H pipe. I had a stainless fabricator box and therefore connect the cut out sections. (FYI, the H pipe on that older Corsa actually intruded into the pipes by about 1/4”, creating a bit of an obstruction in the pipes).
Second, in the pipes aft of the resonator I drilled a bunch of 1/2” holes on the insides of the pipes and similarly had them boxed with welded stainless plates to allow sound mix but not change the exhaust flow. I feel that the modifications were successful in reducing or eliminating the annoyance of the pulsing sounds I noticed. I have no evidence that the modifications change performance in any way.
As Scott noted in an earlier post, if you don't hear such a sound then don't worry about it. Maybe it is just my mind going. But since I noticed it on this system as I had on my older system, I will modify the resonator on this system and see if I can eliminate it. If I ever do the modifications (no one yet seems to have an extra Corsa resonator to borrow or buy) I will take and post pictures of it and report on success or failure. Hope that helped. --Bob

[-=Jeff=-]

yes Bob thanks for that

[XfireZ51]

Bob,

Why not use an LT4 or Magnaflow resonator?

[WARP TEN]

Bob,

Why not use an LT4 or Magnaflow resonator?

No good rational reason not to, but after testing five different exhaust systems on my 93 and concluding Corsa was best for me, I am kind of used to Corsa. I used to use my Quasar Blue as their demo car at shows like Mid America. And I know it it will fit without extra work (other than my mods). Also, I like that it has a straight through pipes yet is effective at cancelling the primary resonance that our engines are known for. So except for the fact I want to modify it to cure another noise problem.... :_)

[XfireZ51]

I believe the LT-4 is straight thru and we know it fits. I have used the Magnaflow resonator on a stock and ported motor. IMO, it works well for anything up to 400rwhp as it did for mine. However, its a 3" inlet. I believe the LT4 is 2.75" which would match up better w the Corsa. Just a couple of alternatives since you've last owned a Z.

[scottfab]

No good rational reason not to, but after testing five different exhaust systems on my 93 and concluding Corsa was best for me, I am kind of used to Corsa. I used to use my Quasar Blue as their demo car at shows like Mid America. And I know it it will fit without extra work (other than my mods). Also, I like that it has a straight through pipes yet is effective at cancelling the primary resonance that our engines are known for. So except for the fact I want to modify it to cure another noise problem.... :_)

I hope you can get a chance to record the sound it makes. A before and after sound track would be instructive.

[WARP TEN]

I hope you can get a chance to record the sound it makes. A before and after sound track would be instructive.

Hi Scott--
I will plan to get a before and after recording. I am most curious to see if it really is audible on a recording. But first I have to get something to record with. Maybe my wife's iPhone (I am am stil a dinosaur with my flip phone). I have not had much time to think about it as I just installed my new lift Tuesday and my daugher is getting married on August 3rd. Eventually I will get around to it. -- Bob

[scottfab]

Hi Scott--
I will plan to get a before and after recording. I am most curious to see if it really is audible on a recording. But first I have to get something to record with. Maybe my wife's iPhone (I am am stil a dinosaur with my flip phone). I have not had much time to think about it as I just installed my new lift Tuesday and my daugher is getting married on August 3rd. Eventually I will get around to it. -- Bob

What, your daughter's wedding is more important than working on the car? :p
I can only imagine your happiness for her. Congrats !!

[WARP TEN]

What, your daughter's wedding is more important than working on the car? :p
I can only imagine your happiness for her. Congrats !!

Well you know how it is. You have to get over certain hurdles to get back to the important things in life.