Exhaust Resonator Question

[edram454]

by the way, I have long tube headers and no cats either... very straight free flowing exhaust like they ran at the ft. stockton record run!!

[Okiedoke]

Originally Posted by WARP TEN

Goldcylon is right. The ZR-1 engine has pronounced natural resonance at two rpm points, about 1800 and about 3400.

Well, that certainly helps explain things. I've been getting these annoying vibrations (okay, maddening vibrations) near these RPMs and my mechanic tracked it down to a busted resonator. So now I need to look for a replacement.

[Okiedoke]

Originally Posted by GOLDCYLON

PM Sent. The difference is you will pick up significant resonance and your exhaust will be louder. The CORSA resionator flows better than stock and you wont have the resonance issue.

Goldcylon, do you have the model number of this CORSA resonator? Would it adversely impact smog tests? Do you know if it's still possible to purchase a stock resonator?

[WARP TEN]

Originally Posted by Okiedoke

Goldcylon, do you have the model number of this CORSA resonator? Would it adversely impact smog tests? Do you know if it's still possible to purchase a stock resonator?

The Corsa resonator would not adversely impact smog tests although visually it is slightly different from the stock one. Lee (LGAFF) has a used Corsa system for sale listed in the parts for sale section. --BOb

[Gunny]

Corsa resonator is 2.5" inlets/outlets. To my knowledge it is not available as a separate part, but I have seen a used Corsa resonator a couple of times over the past 10 years or so.

OEM resonator is 2.75". Again, AFAIK these are no longer available but can sometimes be found used. If you go OEM try to find a 94 or later including the 96 LT4 ... these are the least restrictive and work very well. A good exhaust guy can fab these to whatever setup you have.

Other resonators/X-pipes et al ... I doubt you will find anything in 2.75 diameter but only 2.5" or 3.0". Search for Craig's (Hawaii ZR-1) solution for the center resonator ... I believe he discovered a good substitute.

[RussMcB]

Maybe, as a short term solution, install an H-pipe with 2.75" tubing to put in place of the stock resonator. That will get rid of the rattle. It will be a little louder - Not sure how much, but maybe the stock mufflers will keep the sound level reasonable.

[Gunny]

Originally Posted by RussMcB

... install an H-pipe with 2.75" tubing to put in place of the stock resonator ...

this is actually a pretty good idea. in conversations with several Z-owners I'm learning that the H-pipe installed toward the front and eliminating the resonator might produce better results than an X-pipe. sounds like this might be a good time to give it a try ... if you do, please report your findings.

[C4Ray]

The Resonator keeps the drone down, so if you remove that or replace it, then you will have drone and drone is terrible for long term hearing. Those Corvette engineers back in the day did their research with the stock exhaust ... It is a pretty good system as is!

[Okiedoke]

Originally Posted by Gunny

OEM resonator is 2.75". Again, AFAIK these are no longer available but can sometimes be found used.

There seems to be a 1990 complete exhaust system listed in the registry market place. Does anyone know if there are any differences between the '90 and '91 exhaust? If not, would it make sense to swap out the entire exhaust system instead of just the resonator?

[Gunny]

Originally Posted by Okiedoke

Does anyone know if there are any differences between the '90 and '91 exhaust? If not, would it make sense to swap out the entire exhaust system instead of just the resonator?

Someone more knowledgeable may chime in ... but I think the 90 and 91 systems are essentially identical. I'm fairly certain all the pipe diameters are the same @ 2.75" and that the resonator is the same. Not sure if the 91 still has the twin tip mufflers or not. If so, it would probably be easier to swap an entire exhaust system since it involves no more than unbolting the two pipes from the back of the engine and taking loose 6 hangers ... no need to go to an exhaust shop for welding, etc.

The big advantage is retaining the OEM look without a lot of effort. But, in an effort at full disclosure, the early OEM exhaust systems are rather restrictive (resonator & mufflers) and do not allow the LT5 to breathe as well as the later OEM systems or other, less restrictive 3rd party systems.