You haven't explained how my much "bendier" SideEffects system sounds better w/o a muffler than with. If bends are the cure, I got plenty of them. I'm sure more than your Kart. If bends are the cure, the addition of a muffler wouldn't hurt.

 

Is it possible for it not to restrict flow and be quiet? I have my doubts but would welcome your input. I hate my Borla cat back but don't see many options short of an exhaust designer to spend more than the car is worth to build the magical system. With just the single cat, I can't see how to do anything more without hurting the flow. What would be less noise and not reduce the flow to the point it affects the engine? I understand that it needs a certain amount of flow and more, for more's sake isn't better.

I got the Borla because I wanted a higher flow and 304 or 409SS for durability because I might drive it in the winter and Wisconsin has salt for roads when the snow falls. It also has to support 420 RWHP, give or take and not restrict the flow to the point it hurts the engine. I could care less about the sound so the quieter it is, the better for the wife and me.

 

No, I haven't explained it. I don't know any thing about your exhaust. I don't know what it looks like, I don't know how it's routed, how it sounds, muffs or not...I can't explain the observations that you have made on your car. I can only explain what I've observed on my own various cars and exhausts.

 

Here's what Side Effects look like....(They were designed to hookup to the SINGLE stock Y pipe of an L98 or LTx setup. The initial "splitter" is designed fairly well. It splits flow about as smoothly as our double-barreled throttle bodies. The problems stem from it turning UP the car, firing into a resonator/canister, then expelling 180-deg to the rear. Even the outlet represents one last turn!)


Don't forget BOTH L98s and LTx engine start with 90-deg bends as the down-firing stock manifolds reroute to the rear of the car. Plus, they wind around the transmission, over the rear axle, and at an angle out the back. I think there are lots of bends.

My initial setup looked like this. Headers fired into a dual-inlet/single outlet muffler that was connected to the SideEffects system. Drone was bad in 6th on the highway...which is to say in lower rpms. That was also the case when my stock engine was routed through a main cat and output via targas (mounted in a traditional location).



It's possible we are both right...from the standpoint that a "bendy" system OR cylindrical mufflers end up attenuating mid-bass frequencies....which contribute most to "boomy" tones.

 

I'm sure you are aware SOME people have swapped from Borlas to Corsas in search of better sound. Of course, that's one option.

I might be inclined to bypass the Borlas and consider installing cylindrical resonators in the belly. I've also heard the Magnaflow x-muffler with ONLY LT4 cats and straight pipes. I like that quite a bit too. (I haven't heard that over time after the internal batting has had a chance to break down though...) Resonators/glass packs have the added benefit of being cheap too...so it's not an expensive test. I'd probably try traditional resonators in the longest (12-18") you can find.

I'm sure it also matters whether you're running an automatic/manual and (at what) rpms bother you. I think the drone I experienced was lower pitched that most due to the longer run of the SideEffects. What I forgot to mention (in my post above), is that "boxy" SpinTech muffler may have ADDED drone by allowing frequencies to bounce in a non-batted box. Sound is SUPPOSED to "spin" through internal channels in those mufflers -- which you wouldn't expect to collide with other waves. But, I haven't seen one cut apart...to know what the internal baffles LOOK like. The idea is what you hope for -- to get muffling w/o losing power. There's all kinds of "gimmicky" mufflers TRYING to do the same thing. Another company makes a spiral cylindrical muffler that's supposed to do the same thing.

What I've never gotten out of Vizzard's articles is why particular shapes are better than others in creating/eliminating "restriction". For example, I seem to remember his article saying tapered cylinders were worse than some chambered mufflers. I'm not sure I get that...or if there's some "vested interest" in a particular muffler company requiring him to split hairs on the subject? That said, I can see where expandion...followed by contraction induces non-linear flow that's more turbulent than straight pipe. I'm especially confused how one can add a "terminator box" without inducing the crap sound I feel an "open shape" would cause? Maybe an "H" pipe just beyond headers is the best way to accomplish that -- if it can be made to fit under our cars!

Finally, please make sure unwanted sounds aren't the result of pipe "hum" vs poorly tuned exhaust. I see the entire exhaust system similar to a tuning fork. And, it's being vibrated by the escaping exhaust. That means you could also try a quick experiment of clamping weight to the exhaust pipes...just to be sure system resonance isn't part of the problem. BTW...Adding weight should lower any tones related to the pipes themselves. Weight adds mass which slows vibration.

Oh yeah...If you try resonators (or even a Magnaflow x-muffler) in the belly and aren't quite happy, remember you can add MORE resonators down the line. In my OTHER vehicle, I have two sets (end-to-end) in it's exhaust system). Actually, one, then a bend, then the other.

Have you tried it with JUST the cats and no muffler? (If so, I'm curious if it was louder but with less drone than you have now?)

 

Keep the CAT.
Keep the dual mufflers, Borla Corsa Flo-maters, whatever.
Make sure the exhaust tips are at least and inch beyond the body work as viewed from straight down the rear bumper.

And turn the F**King radio up! Its a Corvette! Not your mamas buick for cripes sake.

 

Damn....that thing is crazy. I can't imagine how that would be any good for power.

 

Yeah....I've been waiting for that comment! LOL I really like side pipes and have consider some alterations. Dumps or just piping (like your Kart) directly to the cover's outlets have been a couple of thoughts. One of these days, I want to drop it and see what it sounds like...Of course, I have to consider terminating exhaust under the car -- for the test (heat) and how realistic the [sound] test would be without getting the outlets near the perimeter of the vehicle.

FWIW, a new member has a supercharged 750hp C4 with this exhaust on it. I wonder if it's 1000hp without!




Oh yeah....Concede that I have more bends yet?!?! LOL

 

I forgot to mention (as you've probably read) that one approach includes the use of larger (input/output) mufflers for your application. If you have a 2.5" system, consider 3" mufflers. I can't remember if I've seen them, but [if I had a "normal" exhaust] I'd consider 4" diameter 18" long canister (cylindrical) mufflers for the belly. Or...there's the option of chambered piping -- if that's made in a size you'd like?

 

Right now, I am a single 3 inch split into twin 2.5.

 

IDK. You definitely appear to have more degrees of bend or more total angular change! You've got 360* on each side...just in that bolt on. But I think mine has more bends; where it goes from one direction to another -even if the angularity of change is slight for many of the bends, I believe it matters that it's a "bend", and it changes the exhausts and audio's direction.

 

As Tom points out, address the obvious first. ANYONE looking at my system who'd recommend efficiency improvement would say drop the sidepipes...and they'd be right.

Assuming you're feeding TPIS/Random cats into a stock Y-pipe center section, I'd want to change that. More directly, it sounds like you are dumping dual 3" header collectors/cats into a single 3" mid-section. Not the best solution IMO. You've only got a 7cu/in cross-section for the middle with over 10cu/in before and after the split. Besides the center bottleneck, you're doing the opposite of what's recommended. If anything, narrow exhaust down the line...to keep it moving.

I think you have two options: Increase the center "Y" to 4" by converting it to a 4" diesel/race muffler (like this) or swap to a 3" Magnaflow X-muffler (like this). Back pressure will drop dramatically and you'll be ADDING sound abatement. I think both will contribute to improving your complaint. I should also add that the x-muffler might to the most if this theory of bends has merit. (It would add two extra bends.)

Your profile says TPIS long tubes which have 3" collectors. That means you can feed directly into the x-muffler w/o reduction/expansion. A muffler shop could add reducers on the back-end to transition down to your rear 2.5" catback. If you weren't "OK" with the quietest possible sound, I'd suggest dropping the Borlas to see what it sounds like w/o them (and with the Magnaflow x-muffler). In fact, if you buy one, ask the shop to drop it off the rack before they connect your catback. Drive it around the block to see where you'd be. You might be surprised.

I don't know anything about the internal construction of Borla/Corsa mufflers but the cases look smaller than other "performance/sport" mufflers. If either/both are filled with batting, either SHOULD be much better...though [clearly] Corsa gets better reviews. Less batting and/or different chambering could explain why Borlas aren't as well-liked. As for my point about avoiding oval/box mufflers (while recommending the Magnaflow x-muffler, consider that it's filled with batting AND it joins both banks. It's not a typical muffler. Plus, I've heard/driven one on an LT4 with muffler eliminators and thought it was stellar.

 

Borla drone solved..
https://www.corvetteforum.com/forums...xperience.html

 

Very creative solution. Of course, I have to ask why you considered having ANY hole in the plugged side? (Except, of course, the inexplicable desire NOT to have a plugged up fancy exhaust! .... which I understand LOL )

We've seen/read about the single/double outlet issue for years...including the factory mufflers. Makes me wonder if it's by lowering output/performance or something to do with the way side-by-side sound waves "merge"? I'll have to dig up my PC speakers and see what the difference is really like. (On PC speakers, there's barely a difference)

 

I have a theory on exhaust drone:
Mufflers with oval cases (e.g. the stock mufflers) have the least drone.
Mufflers with flat cases (Flowmasters, Hooker, etc.) have the most drone.

I believe it is because the flat cases will resonate/reverberate like a bass drumhead. Oval cases cannot reverberate. All the reports on this forum seem to support this theory.

 

Unless you count Borlas....which are oval? Corsa is the only non-factory larger bodied muffler I've seen highly regarded...and satisfying. As a cube becomes closer to a sphere, maybe the effect (of boom/drone) is, indeed lessened. Though I've not seen them in person, Corsas and Borlas look like somewhat smaller cases overall?

Smaller bass cabinets tune to a higher frequency...which means the drone would rise in rpms. If it's high enough (e.g., above "bass frequency"), that's when people tend to call it gone -- like Corsas.

When plugging outlets (as described further above), I have to believe it's like removing 2 of 4 speakers in a room. In audio, halving the number of speakers tends to half the volume. By making the second outlet a small hole, the resonant frequent of that outlet rises significantly.....making it more like a mid-range speaker.

Smaller-body mufflers lean toward the same outcome. I think that's why I like cylindrical shaped components better, the chamber part of their construction is a much smaller portion of the unit -- which means they can't let sound bounce around and cause booming. Plus, they will let SOME straight-line bass frequency through so they sound beefier than chambered/box mufflers.

 

One of the things I've wondered about is whether the union/weld between the flat/rectangular tubing and the actual "sidepipe" is OPEN. If so, the flow might be nearly as good as your Kart.

The (flat) rectangular tubing has a cross-section equivalent between 2.5 and 2.75" round pipe. As such, I allowed for the possibility that the dynos (provided in sales brochures) were reasonable in showing an improvement over stock L98 piping...and even a small bit over LTx systems with stock mufflers.

Since most people would consider performance engine fed into headers and an LTx exhaust "reasonable", that's why I decided to keep them after conversion to a 383. FWIW, they were so hard to find back in 2005, it took constant looking until I finally found a good set in 2007.

A picture of them mounted is in a recent "Let's talk spoilers" thread....if anyone is curious about their appearance. Plus, there's finally been a set/two for sale in the past year. Before that, I never saw them anywhere...that lasted 2 seconds. Kinda makes them hard to turn-loose!

If I did convert to a straight-forward setup (like your Kart), I'd only be able to sell the pipes...w/o the side covers. It's still possible though my target buyer would probably been a humid climate where the pipes have rusted out. (Actually, I met a guy locally who had that very problem. Too bad I lost his contact info!) I think it had to do with the fact, he ran exhaust to the back (after removing the side effects) but left the side covers on because they "looked cool". Really? LOL

I might still have a pic on my phone somewhere! After that, I got over feeling bad about installing a wing on my vette!

 

I just want to thank everyone who has contributed to this thread. I have been reading hear and doing research elsewhere. so here is my plan of attack as soon as it gets a little warmer here in jersey. First try moving my Dynomax/Walker mufflers back further so they are past the rear valance. If that doesn't work Im going look for a set of Borlas or Corsas. I hope to find a used set do to the fact that I just want the mufflers. If im still not happy with that then I will try modifying the mufflers. When I had my original engine I had the headmans that I have now to a stock exhaust with a gutted cat to the Dynomax mufflers I was happy with the sound but the gutted cat was starting to rust out and leak. When I had my engine built it the Dyno Numbers where better than I expected so I wanted to improve the breath ability of the exhaust so I went 2 1/2 out of the headmans to an X pipe where the Cat used to be then 2 1/2 pipes to the same dynomax mufflers.I believe the mufflers are in the same place so the drone is either from the new pipes or the added power of the new engine. thanks again for ALL the input. I know this subject has been beat to death.

 

I think the set up is cool. I hope my "wow" didn't come across as "get rid of it!". I think that it's cool b/c it's period, it's different, and it's side pipes. Also, it looks like the build quality is quite good. I'd think the flow would be compromised due to the very small radius bends...but if the size is big enough...It's probably fine. Changing to something like I made for the Kart would be a lot of work for only a couple hp maybe.

 

Nah....It was more the comment about it not being any good for power! LOL That's OK...I try not to keep my head in the sand the WHOLE day!

Actually, the initial coupler has a nice venturi-style design to it. And, the sweeping bends -- going into the side "rails" -- aren't THAT small of a radius. So, the manufacturer did do what they could to address all the challenges of bringing sidepipes into the 21st century -- while maintaining the ability to please the EPA.

I still think it will be interesting to drop/drive it one of these days....