Aurora40

I'll have pictures up later. But I got the work done today. LT4 resonator, and Dynomax 3" in, 2 1/2" dual outlet Ultraflow SS mufflers.

The work is excellent, it looks very stock and very nice. I'm very happy with the guy who did it. From lifting the car to the fabrication to painting the mufflers, he was very careful and thorough.

When we looked at the mufflers though, they were slightly different than the way they generally work. Instead of a 3" perforated pipe for a short distance that Y'd to dual smaller perforated pipes, it was a huge 3" perforated pipe for about 3/4 the length of the muffler. Then it was just an open chamber to the dual outlets. I guess that should have told me right there it would be loud. The muffler case is already pretty short, but 1/4 of it provides no muffling at all!

The car sounded great coming out of the shop, and not really very loud either. The volume of sound isn't really too much more than stock, you can still hear the mechanical sound of the engine prominently when getting on the gas.

But the resonance.... holy crap... I don't know if it's less or more than some other systems. You can cruise at 60mph in 5th no sweat, and 75+mph in 6th no sweat. But below 2,000 rpm you get more resonance as you open the throttle progressively from cruise level to cruise/slight acceleration. And around 1,500-1,700 rpm it is really jarring when you give it any throttle at all. Enough that my voice would vibrate slightly as I talked. My head was hurting a bit after an hour.

It's possible to drive with little resonance, but you need to be in the right gear to stay in the right rpms. You have to not mind driving at ~2,000 rpms vs shifting to a more relaxed cruise. Cruising with the windows cracked at 60 it doesn't seem too different than stock, there's just a slight burble where there'd ordinarily be more of a drone.

The overall volume level isn't too much higher than stock, it's just that the resonance peaks are much higher. It's not like that all the time, but when it is, geez!!

I'll see if they get quieter after a couple hundred miles, and see how they grow on me in more regular/short distance driving.

But if you want to try the same thing, I would not recommend 3" mufflers. If you use LT1-style tips maybe it would be ok as the muffling would extend the whole length of the muffler.

I will certainly consider changing them out to 2 1/2" in/out mufflers in the future, or maybe even some 50-series Flowmasters. I think if I do, I'd like to get the car dynoed first.

The sound is subjective, I loved the stock sound. This is deeper and burblier, and doesn't have as distinctive a sound over other pushrod 'vettes. IMO, the stock sounds of a ZR-1 and say an LT1 'vette were easily discernable. I'm not so sure my car now sounds any different from a pushrod 'vette with fiber packed mufflers. The sound is good, though, not a bad sound.

415LT5-badZR-1

No pics - therefore:

Aurora40

LOL! I just wanted to feel important...


Here's the LT4 resonator compared to my 1990 (mine was a lot cleaner). Look how significantly the 1990 resonator tapers down! The LT4 seems to be about 2 1/2" through it while mine was about 2" through it. Both are perforated straight pipes inside with fiber packing around that:





Here is what the muffler looks like inside, you can see how it doesn't Y to the outlets:

Aurora40

Here it is all together. The mufflers were highly polished, so they got painted black. Not perfectly stock looking that way, but close enough for me:







Original vs modified:





Like I said, I'm very happy with how it looks. It's a spitting image for stock, except actually the tips are even more perfectly lined up now.

Aurora40

Some sound/video. The before (wasn't fast enough on the camera to get the car at start-up):

http://aurora40.dyndns.org/Hometown/...ust/before.MPG

The after:

http://aurora40.dyndns.org/Hometown/...aust/after.MPG

JoeyGibson

love that license plate

Sgreg

Bob-

Very nice work; I doubt my exhaust guy will cut and weld that good. I am installing Jeals and Random Tech cats and am going to try to use all stock pipe back of the cats ( 2 3/4") with the LT-4 resonator ( 2 1/2 ") and 2 1/2" Flowmaster mufflers. I hope it will produce something a little quieter that your set-up but still produce a decent exhaust system. BTW, anyone know a good exhaust guy in the Houston area ?

Greg.

Aurora40

Thanks! I always love to hear that. I wonder sometimes if it's too esoteric, but then people compliment it. I went to a local 'vette dyno day a few months back, was all C5 and C6 guys, but even they complimented me on the license plate (and the stock exhaust sound).

Cool, let me know how it works out. I still need to see how I like this, but I'm not ruling out doing it again with some smaller mufflers.

Oh, also it was $520 for all the labor and the Dynomax's, and I paid $70 shipped for the resonator from a forum member. Seems like if you get the timing right, sometimes you can get stock exhaust stuff for free, though. So it was cheaper than buying and having installed any other exhaust option. Plus it looks stock (I know, no one cares...)

93RubyZ

Looks nice and sounds even nicer!

You oughta post your sound clips to this post so they can all be collected together:

http://forums.corvetteforum.com/show....php?t=1425360

Greybeard ZR1

That setup looks great. Very much stock looking, but the sound is nasty.
I like the car, and plate too. Like my plate, (4CMLT5), to people who don't know, it doesn't look like a vanity plate. But to those who know what a ZR1 is, it sends the message.

BTW, have you read the article by Hib Halverson (on the ZR1 Net site) on the custom exhaust he pieced together? I haven't heard the results, but he claims a good increase in power, great sound, and minimal resonance. Check it out. It may give you some ideas about other muffler choices.

I've got headers, no cats, Xpipe, and 3" B&B's. So, let me tell you what REAL RESONANCE! is........

kmoudy

NOT TOO LOUD...damn..it scared the little dog here in my office..
you'll need to learn sign language in a few days..
one word..Corsa...but i love your plate

Aurora40

Yeah, I'd seen that. It seemed like the resonator he used would be the big bottleneck though. That's why I thought the LT4 would be a good choice, it should do a decent job of sound attenuation as it's OEM, and it's not so restrictive. I think my muffler choice just wasn't quite on target.

I just kept thinking if I went 2 1/2" I'd regret not trying 3", though I suppose if 2 1/2"s were on the edge of being too loud, I'd probably be glad I didn't go 3". And I kept thinking if I went Flowmasters, I'd regret not having straight-through.

LOL... I don't know what I was thinking saying it wasn't too loud. Though it didn't seem too loud to me. Maybe I was expecting the ground to shake or something?

I'm warming up to it though. It sounds pretty good, my 30 minute drive to work today was fine, it didn't bother me. And the car definitely feels like it gained some power all over the band (though I haven't run it out to 7 grand yet). Even below 2,000 rpm it feels more responsive when I press the gas.

tomtom72

Sweeeet sound Bob!

Looks like the stock/sleeper set up...I'm in that camp...stealth!

Nice growl at idle and plenty bark on the blip!

Sorry for the Q's:o
you re-used the stock tips?
The new mufflers were too shiney, so black'em out...right?
The resonator from the LT4 fits the stock pipes??? or you need new pipes?

Resonance seems to be 1500 to 1700 in 6th? less than 1500 rpms in 6 is where I cruise I think? Can't remember it's been so long that I haven't driven my car!

Maybe I try this but with flowmasters....I have no top end work like you do so it proly will not matter to my car...for sure like the sound!

to you on this job!!

Tom

Aurora40

Hey Tom,

Yes, those are the stock tips. They were cut off the original mufflers and welded on. The LT4 resonator is exactly the same dimensions, just with less pipe taper. It fit up perfectly.

I had to go with Dynomax mufflers to get the outlet spacing required in order to retain the stock tips (because I wanted straight-through mufflers, thus eliminating Flowmasters). They only come in aluminized cases or in highly polished stainless. So yeah, they were crazy shiny and would have looked very weird. So they got painted flat black for a more stock appearance.

If you use Flowmasters they would probably match up just fine without painting as they are a dull metal finish, not shiny. You might paint the end of it since that's how the OEM mufflers are.

If you don't use stock tips, or if your stock tips are the LT1 style, then the muffler choices really open up to you. The LT1's just require a center outlet, no spacing to deal with, and non-stock tips, you don't have to retain the stock spacing in which case some Magnaflows or something would work too.

The resonance really was killing me on the way home from the shop, though it was about 65 miles from me. Since then it hasn't bothered me too much, though it is certainly more than stock. I would guess with some smaller mufflers it would be better, though. Really, the resonator is 2.5", so I don't imagine having 2.5" mufflers would hurt much.

cadillac531

Bob:

It sounds BOSS!!!! I love the fact that it looks stock, yet sounds like it's ready to feast on some poor unsuspecting ricer.

Constantine

Aurora40

Thanks! I'll try to get a few more sound clips. Unfortunately it's pretty noticeable even at idle, so a ricer would have to be just about deaf to be unsuspecting!

tomtom72

Thanks Bob for the info.

I was liking to keep the 90 tips on my 90. The more I looked at what was out there in Corsa & Borla & B & B, I was liking the 90 tips even more as all the other tips from the big dogs didn't hit me right....I guess I'm the wierd one but I like the way the stock 90 tips look. The only other tips I really like were from I guess the LT1's and the LT4's. They are the single large rectanglular ones that fill the whole bumper cut out....but I figured I shouldn't put those on a ZR-1 until I think I saw them on some late mod ZR-1's and I really liked the look. Did the 94-95 Z's have single sq tips??

The resonance would kill me as mostly my rides are loooong.

Maybe I get away with the LT1/4 tips and use your idea for the LT4 resonator and any 2 1/2 " single outlet muffler like flowmaster or some other generic brand.

Thanks for the R & D
Tom

Aurora40

Hey Tom, I believe ZR-1's from 1992 and up had the single rectangular tip. So if you like that, it would be easy to find mufflers like that. However, the Dynomax's I used also come in a 2 1/2" inlet size, and there are some Flowmasters that would probably work in that size with dual outlets.

Here are a few more comparable sound clips. I tried to take them in the exact same parking lot, but there was a church service going on, so what can you do... It also seemed there was a bit of wind noise the camera was picking up. It wasn't noticeable at the time, though, and wasn't a windy morning.

Accelerating away

Stock: http://members.aol.com/corvettezr119.../accelrear.mpg
Modded: http://members.aol.com/corvettezr119.../accelrear.mpg

Peeling out

Stock: http://members.aol.com/corvettezr119...ps/peelout.mpg
Modded: http://members.aol.com/corvettezr119...st/peelout.mpg

tomtom72

The sound on your car is soooo choice!

Yea I thought that the later model Z's used the single tips. I like that look...kind of reminds me of my 72 LT-1 after I put the stock sys back in....the side pipe covers were getting too expensive

Aurora40

I had to watch those clips a bunch (as I can't accelerate the car away from myself to hear it). The car sounds pretty much the same to me in the befores and afters. I suspect it might just be a little more volume and a little more burble. They actually don't seem any louder when I floor it. I still mostly hear the mechanical sound of the motor and the tranny/rear. They sound much like stock, but more so, which is a good thing as I liked the stock sound.

Also, FWIW, my wife didn't seem to think it was too loud at all in the car. I really thought it would bother her. Though she also said she always thought the car was loud. I guess it would help to hear what some other cars sound like inside and out.