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My New Exhaust System

Rogue

Well-known member
Joined
May 18, 2003
Messages
312
Location
Orange County, CA
Corvette
1991 Turquoise Metallic Coupe
I finally installed an aftermarket exhaust on my 1991 L98.

It's the Dynamax Ultra-Flow Stainless Steel Mufflers and companion Y-Pipe with cross-flow tube. These ones:

http://www.madvet.com/shop?frame=1.119.983

Opinion:
The build quality of the exhaust is pretty good considering the price. The stainless steel on the mufflers where of very high quality. The exhaust tips however are kind of cheap looking. Although, nowhere near as cheap as the factory ones. I paid about $510 plus shipping, and another $100 for professional installation.

The sound is very much improved from stock. It has a very deep rumble at idle and part throttle. Now it sounds like a mean-ass V8 powered muscle car. Yet, at WOT, the sound seems subdued. Just barely louder than the factory. Hmmm......weird. I was concerned with resonance and this is why I wanted the Y-pipe with the crossover, which is suppose to "eliminate" it. Well, like most things in catalogs, there's a bit of exhaggeration in their description. There is resonance between 1,500 to 2,000 RPM. However, it's there only when the transmission shifts to top gear and the engine is under load (like climbing a hill). In any other situation, there is very little to no resonance at all. At idle, there is no resonance. At cruise on flat roads (with little engine load) there's no resonance. At engine speeds above 2,000 RPM, which is where my engine is at during freeway, the exhaust is as quiet as the stock mufflers! This was a pleasant surprise as I didn't want the low droning exhaust sound while cruising down the highway.

My only issue is that the mufflers fit a bit off. The right muffler (while facing the back of the car) sits higher than the left. According to my installer, who is a Dynomax dealer as well, this is normal on all the Dynomax mufflers he has installed on C4's. It's because of the tooling Dynomax uses to manufacture the mufflers. I don't know the truth to this but he showed me that the mufflers just bolt on and are none adjustable. Once bolted on, there's little in the way of movement or leeway to allow adjustment of the muffler height. We tried our best but just couldn't get the installed height even between the two mufflers.

Conclusion:
I'm 90% happy with the mufflers. It certainly looks quality for its relatively inexpensive price of $510 including Y-pipe. The sound is just perfect for me.

However, I'm slightly disappointed that there is still resonance. Albeit the resonance is located in a very narrow RPM band and only happens when the engine is loaded at top gear. I am more disappointed about the muffler height difference. Most people won't notice it but I do and that's all that matters I guess.

Would I buy this exhaust again? Since I have an older Corvette, the exhaust of choice isn't available--the Corsas. Thus, I couldn't get that. However, next time I may try the Magnaflows instead. For the price however, I think the Dynomax is worth a look.

What do you guys think?
 
I put the same mufflers on my '89 Convertible. The resonance was so bad that I took them off and replaced them with the Force 50 Flowmasters. Much better, but not the mean growl of the Dynomax's. I am selling the Dynomax's at a good price. They were on the car for 2 months and about 100 mi.


Doc
 
Boy am I glad to read this post. I too have an 89 convertible with the stock rear axle ratio of 2:59 and AT. I run about 1700 rpm at 70 MPH so I bet the resonance would be terrible! I wonder if any of the other exhaust systems are any better?

I was thinking of getting a stainless steel cat-back MagnaFlow system. They really look great but I still worrry about that darn resonace. So far I stll have the stock system. Any opinion on these?

Radar :w
 
Radar, I have stock axle ratio and AT too. But at 70 mph, my RPM's are just at 2,000. So, no resonance. The fattest part of the resonance is at 1,500 to 1,800 RPM and only under load (top gear, climbing up hill). If the tranny shifts down to a lower gear, the resonance disappears. And once the climbing ends, the resonance goes away. It's weird but very consistent. So at highway speeds of 65 mph and above, no resonance or loud exhaust sound at all. Of course, I'm also using the Y-pipe with the crossover tube so that may help.
 
Resonance

I too have Dynomax mufflers. The were on the car when I bought it. The set up is a bit unorthidox but seems to work well. At idle I have a slight grumble, definate low pitch V-8, at WOT I have almost a growl, the little Hondas and Nissans ,ect. around here Have learned when I'm really on it. Their fart cans (OOPS can I say that) alone doesn't put them in the league with a Vette.

The only time I get resonance is when the top is off, but then with the wind noise the radio always goes up anyway.

What one of the previous owners had done was cut the Cat off at the front edge of the CAT (the pipe is rounded the shape of the CAT), welded in a Y 2 1/2" OD I think, and then had straight pipes bent and welded in to the stock muffler locations. Every thing is welded up and fits nice the tips are in line and right where they should be. There are no leaks. It looks like a big X basically. They should have done away with the stock front Y and eliminated the pre CATs, but you can tell they basically told the shop what they wanted. All the welds are Top Notch thats why I think a shop did it.

I don't know about the way your rear Y pipe looks, it could just be the angle of the picture, but it seems awful low. I can see what you mean about the offset in height. I think mine are a little different model, straight in dual straight out. They added an single oval tip. One thing I did notice about mine one muffler is Dynomax down the other is Dynomax up (the stamped side), maybe it fit better that way, can't remember which is which.

:pat
:CAC
 
Man, I bought some Dynomax super Turbo mufflers off ebay.... Im not sure if they are somehow broken... but they are just about as loud as stock. A nicer deeper rumble, not much resonance at all. BUT THEY ARE JUST AS LOUD AS STOCK. I was so sad when the car came on at the muffler shop. Im waiting to see what it sounds like when i get my headers and my x-pipe in.

As for the heights, the one on the passanger side was all over the place. My muffler shop (Noels if you live in miami) is very good. They heated up a part of the y pipe and applied some pressure till both mufflers were at the same height. The tips are pretty cheap, when the x pipe is done, im going to get the tips straightend out. They were adjusted to what we thought was straight while the car was on the lift, but once i got it home it looked off.

Are these mufflers supposed to be this quiet. My stock mufflers were barely on the car, the insides of them a pile of broken tubes all rusted up. The drivers side muffler wasnt sealed at all to the y pipe, just flopping around. AND YET these new mufflers are just as quiet, if not quieter. I dont know whats going on, could it be the resonator? Thats is job right, to cancel out some sound? Clogged cats maybe?

thanks,
-chris
 
Hrtbeat1, yes I did notice the Y-pipe is awful low. There's about 6" of ground clearance. But since they sit parallel to the rear wheels, I don't have to worry about speed bumps or driveways. Just debris on the road that I may drive over. But, it's not any worse than the ground clearance of the front spoiler. I've driven it about 200 miles and so far no issues with ground clearance.

I'm quite happy with the sound of these mufflers. They're aggressive sounding at the right times but out on the highway, they're as quiet as stock. I've heard other V8 powered cars with loud exhaust and they attract too much attention to themselves especially when they get on it. Traffic cops here are paranoid about speeding and they enforce speed laws as much as they can. I already got one too many speeding tickets.
 
militant_x said:
Are these mufflers supposed to be this quiet. My stock mufflers were barely on the car, the insides of them a pile of broken tubes all rusted up. The drivers side muffler wasnt sealed at all to the y pipe, just flopping around. AND YET these new mufflers are just as quiet, if not quieter. I dont know whats going on, could it be the resonator? Thats is job right, to cancel out some sound? Clogged cats maybe?

thanks,
-chris
It would seem like it since our findings are similar. They make more V8 sounds than stock but as soon as you go WOT they quiet down to near stock levels. It surprised me too. I like it actually. One thing that worried me was the exhaust sound would be loud and constant enough so that I'd get tired of it. But that isn't the case. I don't know how these young kids can stand the low, grating noise of their fart cans that stays on constantly.
 
I have the 1133 CFM Dynomax Welded SS mufflers which are actually higher flowing than the stainless (These are the highest output Dynomax makes)

I Love Em!

The Magnaflow however will be my next exhaust simply because of the looks of them. They do a wonderful job with double rolling and stainless.

Mine are the ZR-1 tips single wall. Im hoping I can actually stick Magnaflow tips on my Dynomax mufflers then I"ll be a happy camper.

Mine also resonate a bit but I actually like it. To me its reminding me to HIT THE GAS IM GOING TO SLOW LOL. Its like the car saying Im bored ugh... LOL
 
ok, my 2cents. I've had the dynomax supers for about 8+ years or so with the crossover.
Mine also were cock-eyed from the shop.
When I got home, I got under and adjusted the muffs and the pipe and they've been hanging right ever since.
What needs to be done is to LOOSEN everything enough to be "muscled" in place,
including the y-pipe. Line every thing up by eye, tighten and you should be good.
 
Maybe I have had side pipes for too long-

I like resonance. I need resonance.

Seriously, glad that your pipes worked out for you. I find myself in the same boat- 90% happy with products from the aftermarket. I think I am just a perfectionist though!!!

I wonder what side effects could do for the C5....
 
Rogue said:
I finally installed an aftermarket exhaust on my 1991 L98.

It's the Dynamax Ultra-Flow Stainless Steel Mufflers and companion Y-Pipe with cross-flow tube. These ones:

http://www.madvet.com/shop?frame=1.119.983

Opinion:
The build quality of the exhaust is pretty good considering the price. The stainless steel on the mufflers where of very high quality. The exhaust tips however are kind of cheap looking. Although, nowhere near as cheap as the factory ones. I paid about $510 plus shipping, and another $100 for professional installation.

The sound is very much improved from stock. It has a very deep rumble at idle and part throttle. Now it sounds like a mean-ass V8 powered muscle car. Yet, at WOT, the sound seems subdued. Just barely louder than the factory. Hmmm......weird. I was concerned with resonance and this is why I wanted the Y-pipe with the crossover, which is suppose to "eliminate" it. Well, like most things in catalogs, there's a bit of exhaggeration in their description. There is resonance between 1,500 to 2,000 RPM. However, it's there only when the transmission shifts to top gear and the engine is under load (like climbing a hill). In any other situation, there is very little to no resonance at all. At idle, there is no resonance. At cruise on flat roads (with little engine load) there's no resonance. At engine speeds above 2,000 RPM, which is where my engine is at during freeway, the exhaust is as quiet as the stock mufflers! This was a pleasant surprise as I didn't want the low droning exhaust sound while cruising down the highway.

My only issue is that the mufflers fit a bit off. The right muffler (while facing the back of the car) sits higher than the left. According to my installer, who is a Dynomax dealer as well, this is normal on all the Dynomax mufflers he has installed on C4's. It's because of the tooling Dynomax uses to manufacture the mufflers. I don't know the truth to this but he showed me that the mufflers just bolt on and are none adjustable. Once bolted on, there's little in the way of movement or leeway to allow adjustment of the muffler height. We tried our best but just couldn't get the installed height even between the two mufflers.

Conclusion:
I'm 90% happy with the mufflers. It certainly looks quality for its relatively inexpensive price of $510 including Y-pipe. The sound is just perfect for me.

However, I'm slightly disappointed that there is still resonance. Albeit the resonance is located in a very narrow RPM band and only happens when the engine is loaded at top gear. I am more disappointed about the muffler height difference. Most people won't notice it but I do and that's all that matters I guess.

Would I buy this exhaust again? Since I have an older Corvette, the exhaust of choice isn't available--the Corsas. Thus, I couldn't get that. However, next time I may try the Magnaflows instead. For the price however, I think the Dynomax is worth a look.

What do you guys think?
I’m with you on your Dynomax. I also went through 4 sets of mufflers in 30 days before I put my stock ones back on. The resonance was totally unacceptable for me. It made me feel either that I didn’t want to drive the car or that when I did I was making excuses for the resonance when I had someone else in the car with me. Plus, the resonating sound gave me a headache.



I tried Flow master 2 chambers, and then 3 chambers. Both were terrible. I then installed Borla, and then Dynomax. As far as resonance, they were just as bad. I had both the Bolas and the Dynomax on the car for about two weeks each before I took them off. Called both manufactures and raised hell on there unacceptable products performance. Sent back the mufflers, and both, Borla and Dynomax refunded 100% of my money back, and I even had them pay for the shipping.

As for the Flow master’s, the manufactures were ridiculous to take to. I don’t think they new one end of the muffler from the other. I gave up on them. I had to eat those.



However the good news is, last month I purchased the Magnaflow mufflers. Found them on EBay from a company called Performance Peddler. The Phone number was on the EBay page. I called them direct, and for a total of $345.00, I had them sitting on my front door step with 3 days.

It took all but 45 minutes to install the two mufflers as they came with a section of pipe welded onto the muffler and clamps. I drove the car for an hour, and then drove it right to a muffler shop and had them welded on. Exterior sound is great, but I all the other mufflers sounded pretty good as well. HOWEVER, the interior resonance noise is at least 80-90% better than the others. The interior sound and resonance at all RPM levels is very acceptable.

I still kept my stock mufflers, but this time I don’t think they’ll go back on.



Funny, I didn’t realize how bad the resonance was on all the other mufflers until I put the stock ones back on. I would say that the Magnaflow are about 20-30% louder on the outside of the car than the stock mufflers. But the resonance is about 5-10% louder on the inside of the car than the stock. (And the stock mufflers had virtually no resonance)

All in all, I’m very happy driving the car now – and that’s what counts for me!
 
Last Satuday I just installed a Magnaflow SS catback system, $406 shipped to my door.

I took off the 7 year old Dynomax Super Turbo cat back, resonance is the same but the low end is deeper.

Sound clip

http://webpages.charter.net/walshb/SONY018.mpg
 
C4 Exhaust

I just bought a Borla 2.5 cat back system. My original exhaust is still in great shape since it was an Arizona Vette. I'll let you know how it sounds. If anyone is interested in the stock system let me know.

The New Guy, Vettetrn
 
LD85 said:
Last Satuday I just installed a Magnaflow SS catback system, $406 shipped to my door.

I took off the 7 year old Dynomax Super Turbo cat back, resonance is the same but the low end is deeper.

Sound clip

http://webpages.charter.net/walshb/SONY018.mpg

Looks good, sounds good :beer I gotta figure out how to do one of those :L I'm sure it sounds a lot different under power though, mine sure does and I still love my Big Borla's.
DSCMeanBackside365.JPG


Damn....Those 315's don't look like much from this angle do they ;LOL
 
The Borlas have a deep mellow sound. The other nice things is that I don't have to blast my stereo or yell to my passenger driving with the top down. Did I notice a difference in performance...Little to Moderate.

Cheers
 

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