Exhaust Drone! - Page 3 - CorvetteForum - Chevrolet Corvette Forum Discussion


C4 Tech/Performance
L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Exhaust Drone!

Reply
 
 
 
Thread Tools Search this Thread
Old 12-26-2017, 08:17 PM   #41
Tom400CFI
CF Senior Member
 
Tom400CFI's Avatar
 
Member Since: Aug 2004
Location: Park City Utah
Posts: 11,791
Thanked 379 Times in 341 Posts
Default

Quote:
Originally Posted by aklim View Post
I was hoping someone could show me what they did for a car like mine. I have the TPIS LT headers that go into the Y pipe so I am not sure how to put a H pipe in that unless you remove the Y and install some sort of H pipe.
You don't need an H or X when you already have a single exhaust. The pulses should be able to perform a similar function where the "y" joins as in an X or H pipe; expand.

I think what the Corvette needs the most is more BENDS in the system, to reduce that hummmm noise that is made by the even firing of 8 cylinders. Just a theory though...

Last edited by Tom400CFI; 12-26-2017 at 08:18 PM.
Tom400CFI is offline   Reply With Quote
Old 12-26-2017, 08:41 PM   #42
gerardvg
CF Senior Member
 
gerardvg's Avatar
 
Member Since: Aug 2009
Location: Melbourne, Australia Victoria
Posts: 2,964
Thanked 82 Times in 82 Posts
Default

I have headman headers on my 85 383 engine, only standard mufflers keep the drone away. Is a nice and quiet ride with the standard mufflers no drone at all.

Last edited by gerardvg; 12-26-2017 at 08:41 PM.
gerardvg is offline   Reply With Quote
Old 12-26-2017, 09:16 PM   #43
69427
Tech Contributor
 
69427's Avatar
 
Member Since: Jun 2004
Location: I tend to be leery of any guy who doesn't own either a chainsaw or a handgun.
Posts: 10,584
Thanked 124 Times in 107 Posts
Default

Quote:
Originally Posted by aklim View Post





Not sure how I would go about doing that since the Y goes into the cat
Here's my H pipe. Connects the two collector reducers at the front of the pipes leading to my Y pipe at the back of the transmission. The crossover is removable by undoing the band clamp at the RH collector side, and then rotating/ pulling the crossover off if needed.




Made a significant reduction in drone, and according to Vizard the crossover here is usually worth about 3-5 horsepower improvement. A worthwhile endeavor, IMO, at only a pound and a half weight penalty.
69427 is offline   Reply With Quote
Old 12-26-2017, 09:17 PM   #44
GREGGPENN
CF Senior Member
 
GREGGPENN's Avatar
 
Member Since: Nov 2003
Location: Overland Park Kansas
Posts: 11,007
Thanked 93 Times in 90 Posts
Default

I'll throw some additional perspective into this thread. Through my 18-yr ownership, I've had SIX exhaust combos.

Stock L98
Stock, main cat, Targa Mufflers
Stock, bullet cats, main cat, Targa Mufflers
Headers, bullet cats , Y-pipe, Spin-Tech Muffler, side pipes (2.5")
Headers, bullet cats, Y-pipe, main cat, side pipes (2.5")
Headers, bullet cats, Y-pipe, side pipes (2.5")

Three of these six combinations were annoying. Three had marked "drone" at cruising rpms....the 2nd, 4th and 5th combo. And, it's not necessarily what you'd expect when you consider more is less...meaning more components to dampen = less drone. Consider the final config is way better than the two iterations prior to it.

Intuition MIGHT suggest that removing components should increase drone. Yet, when I eventually removed a "belly" attenuator (in my 383 setup), the sound improved dramatically. Granted, my setup is somewhat different due to the total system length but Matt has a point when talking about the total "system resonance". When you change mufflers or add an "H" or "Y" pipe, you're changing the overall tuning/resonance of the system.

My newest theory piggybacks on Vizzard's tuning theory. He points out the addition a "terminator" box can make a longer system "look" like a shorter one when tuning for power. For reasons beyond the scope of this thread, lengths in header/exhaust piping can affect the "tuning" of exhaust for power. The wave theory involved in this seems likely to (at least partially) correspond to sound tuning.

My point borrows from my knowledge of bass cabinet tuning. It's not just the length but also diameter that affects frequency of "tuning" for a PORTED bass cabinet. (An internal tube focuses maximum loudness/resonance at a certain frequency. Music near that frequency get's amplified. Ironically, dampening material must be used to prevent unpleasant "drone" in bass cabinets.) When building an exhaust system, the diameter and length HAVE to play a part in the overall drone/tone. If you've ever heard 2.5" vs 3" exhaust, you'll know what I mean.

I think bullet cats (at least partially) disrupt resonance waves in the exhaust. There body size is so small additional resonance of their chamber size doesn't add sound back in. In other words, bullet cats are better than main cats. I would add that larger bodied mufflers increase the POSSIBILITY of drone from their chamber size.

Whether it related to the dynamics of wave theory (ala terminator box) or tuning (more similar to bass box...or musical instruments), the introduction of a muffler may actually HURT. Most performance mufflers don't contain packing or significant baffling. The combination of the change in diameter PLUS the lack of real attenuating can create a "tuning" point that may add to drone versus subtracting it. I disagree with the poster who claims the diameter won't affect the result. L98's and LT1's have essentially the same engine but different diameters of exhaust. And they OFTEN don't have the same results when adding specific mufflers.

"H" pipes are different than "Y" pipes in the method they use to vent gases to the opposite "bank". I think "H" pipes add more "system volume" to the opposite side. By that, I mean air volume...or space. A large increase/decrease in length/diameter IS going to shift that optimal tuning frequency where "drone" happens....where the system is loudest. Like speaker cabinets, packing/batting will eliminate the echoing/bouncing of sound to create something more pure. But packing also reduces the extra volume of the resonance tuning.

Are you following me?

When you add a muffler/converter -- and the body is large enough -- you may change the harmonic frequency of the entire system. It may be good/bad in terms of performance....when you consider what Vizzard is saying. It also may be good/bad in terms of sound FREQUENCY of the system.

The first thing I'd recommend to anyone unhappy with their system is to REMOVE any performance muffler and observe the result. Clamp in a "test pipe" if you want to keep things cheap...and avoid a trip to the exhaust shop. Next, if you're considering the choice of a "Y" or "H" pipe, consider the "H" pipe is likely to make a bigger difference in terms of performance AND sound. When I considered the standard belly "Y" pipe of an L98 couldn't be THAT much different than a "Y" pipe on a dual setup, that's gotta be wrong. Longer runs of "resistance" create more OVERALL resistance. Plus, they do the OPPOSITE of a terminator box....they definitely can't create a pressure drop. Pressure seems likely to get HIGHER. I wonder if that actually aggravates drone?

Anyway, I would suggest smaller-bodied mufflers and/or "H" pipes when considering your options for changing sound. Corsa mufflers are internally smaller. If you listen to glass packs, their sound isn't totally different that Corsas either. Listen enough and you'll hear how larger-bodied mufflers "add" sound -- like a tuba.

The second setup (above) was loud because it sent the highest pressure impulses into the large body of a main converter. That was largely mitigated by (re)installing front bullets. When I finally removed belly components in my 383, the sound improved because I removed the resonance "chamber" in the middle. Side exhaust is so long...and has enough bends, that midrange volume is killed. Low frequency is still present because of the extreme length of the system.

Maybe some of this might spark an idea in your minds? For me, I need to consider that I killed some of my topend performance BECAUSE I don't have anything like a "terminator" box anymore. I have "longtubes" on the back-end...just like the "front-end". While I'm thinking about alternatives to address that, maybe you guys should consider the same -- when considering how you might change your exhaust.

Don't just consider sound, consider performance. "Vizzard exhaust tuning" is worth googling. One of the biggest things I was shocked by is that 100cu/ft of air weighs 38 tons. Really? I remember something like that in college but still hesitate to believe THAT much weight! Knowing how much air weighs, that there are fore/aft exhaust waves, and that the system presents resistance, makes it fairly hard to consider anything you do will end up more than an accident!

THAT ought to help, right!

GREGGPENN is online now   Reply With Quote
Old 12-26-2017, 09:28 PM   #45
69427
Tech Contributor
 
69427's Avatar
 
Member Since: Jun 2004
Location: I tend to be leery of any guy who doesn't own either a chainsaw or a handgun.
Posts: 10,584
Thanked 124 Times in 107 Posts
Default

Quote:
Originally Posted by ddahlgren View Post
I have a drone without 4 tube headers. And the solution is?
Same solution. It isn't the headers that are causing the great majority of the problem. It's the 8&4 and the 5&7 sequential firing cylinders exhaust dumps that cause the increased instantaneous noise and mass flow. The H pipe, installed as far forward as possible, reduces the double exhaust mass dump/noise, and increases the frequency of the noise that the mufflers have to contend with. It's easier to muffle/filter a low amplitude-high frequency noise than the opposite (a high amplitude-low frequency noise).

IIRC Chevrolet put crossover H pipes on production vehicles (with the stock cast iron manifolds) way back when.
69427 is offline   Reply With Quote
Old 12-26-2017, 09:29 PM   #46
aklim
CF Senior Member
 
aklim's Avatar
 
Member Since: Jul 2004
Location: Hartford WI
Posts: 12,426
Thanked 525 Times in 516 Posts
Default

Quote:
Originally Posted by Tom400CFI View Post
You don't need an H or X when you already have a single exhaust. The pulses should be able to perform a similar function where the "y" joins as in an X or H pipe; expand.

I think what the Corvette needs the most is more BENDS in the system, to reduce that hummmm noise that is made by the even firing of 8 cylinders. Just a theory though...
IOW, "You're FAWKED". Only way is to change the mufflers via something that isn't restrictive and quieter aka Corsa.
aklim is online now   Reply With Quote
Old 12-26-2017, 09:32 PM   #47
ddahlgren
CF Senior Member
 
ddahlgren's Avatar
 
Member Since: Dec 2008
Location: Mystic CT
Posts: 2,540
Thanked 47 Times in 45 Posts
Default

Air 0.0765 lb/(cu ft)) according to ISA (International Standard Atmosphere).
times 100 is 7.65 lbs. Mr Vizard as usual is wrong again. It is a long reach to 38 tons

https://www.thoughtco.com/density-of-air-at-stp-607546
ddahlgren is offline   Reply With Quote
Old 12-26-2017, 10:16 PM   #48
69427
Tech Contributor
 
69427's Avatar
 
Member Since: Jun 2004
Location: I tend to be leery of any guy who doesn't own either a chainsaw or a handgun.
Posts: 10,584
Thanked 124 Times in 107 Posts
Default

Quote:
Originally Posted by Tom400CFI View Post
You don't need an H or X when you already have a single exhaust. The pulses should be able to perform a similar function where the "y" joins as in an X or H pipe; expand.

I think what the Corvette needs the most is more BENDS in the system, to reduce that hummmm noise that is made by the even firing of 8 cylinders. Just a theory though...
Tom, I respectfully disagree with several of your points.

More bends equal more restriction to flow. Increased restriction equals more backpressure.

A Chevy engine is even firing, but the exhaust pulses per side are not.

Expansion is not possible unless the pipe cross sectional area change (at the Y) is greater than the increased exhaust mass due to the combining of the two bank pipes.

A Y pipe puts the crossover position further back than an H pipe, resulting in lower efficiency.
69427 is offline   Reply With Quote
Old 12-26-2017, 11:01 PM   #49
ddahlgren
CF Senior Member
 
ddahlgren's Avatar
 
Member Since: Dec 2008
Location: Mystic CT
Posts: 2,540
Thanked 47 Times in 45 Posts
Default

A 2.5 dia. pipe is greater than 2 1.75 pipes in area so what restriction?
ddahlgren is offline   Reply With Quote
Old 12-27-2017, 12:04 AM   #50
Tom400CFI
CF Senior Member
 
Tom400CFI's Avatar
 
Member Since: Aug 2004
Location: Park City Utah
Posts: 11,791
Thanked 379 Times in 341 Posts
Default

Quote:
Originally Posted by 69427 View Post
More bends equal more restriction to flow. Increased restriction equals more backpressure.
I know. I believe that it can also make for a dramatic change in sound quality and character. Still, you can offset some reduced flow with a larger diameter pipe. Depending on the person/car/goals, the trade off may be worth it. It is for me. Great power is part of the "experience". Fantastic sound is also, a big part of the "experience". I'm O.K. giving up a few hp for fantastic sound.



Quote:
Originally Posted by 69427 View Post
A Chevy engine is even firing, but the exhaust pulses per side are not.
I know. The even firing is what creates a tone or "pitch". The "hummm" sound that IS the droning noise. The syncopated pulses are not "drone". That sound is the major part of the luscious V8 sound that we all like.



Quote:
Originally Posted by 69427 View Post
Expansion is not possible unless the pipe cross sectional area change (at the Y) is greater than the increased exhaust mass due to the combining of the two bank pipes.
While I don't think that expansion occurs ideally, it occurs. First you have exhaust from ~2.1" pipe, exiting into a ~2.75" pipe, or more generally, from a small pipe into a bigger pipe -which could also be called a "chamber". If the chamber isn't enough volume, immediately after that, it expands into the front of the cat. Anyway, also, the syncopated firing exhaust "chunks" from each side don't hit the Y at the same time, so while there is a void from one bank, there is a "chunk" from the other. Is it ideal? No. Is it less ideal than most ill placed, ill sized H pipes? Doubtful. A dyno would tell the story.



Quote:
Originally Posted by 69427 View Post
A Y pipe puts the crossover position further back than an H pipe, resulting in lower efficiency.
Well that depends entirely on how you build the Y, or how you build an H system...doesn't it? However you build it the efficiency of it's location depends on the RPM range that you're looking for efficiency. Vizard says that for good power the secondary pipe is far more important than header primary length. He cites secondary pipe lengths of up to 50" in his article HERE -about 1/4 of the way down. But lets face is; basically no one on these forums has a properly built and tuned "zero loss" exhaust, so stressing over H vs. Y merge points is probably not too relevant to most posters here.



I'm no "Acoustical exhaust engineer"...but I've done a fair bit of exhaust experimenting for sound. Look HERE, AND HERE.... HERE TOO

I believe that I've found an important factor to great sounding exhaust. Bends. My benchmark was set years ago with '80's 5.0's and my own 3rd Gen TA that had shorty headers, a mediocre "y pipe, 3" single into a 1 > muffler. Sounded just like this:



...it had lots of bends in it (compared to a Y-Body exhaust) and it had no drone. Mmmm-MM!

Last edited by Tom400CFI; 12-27-2017 at 12:09 AM.
Tom400CFI is offline   Reply With Quote
Old 12-27-2017, 05:03 AM   #51
GREGGPENN
CF Senior Member
 
GREGGPENN's Avatar
 
Member Since: Nov 2003
Location: Overland Park Kansas
Posts: 11,007
Thanked 93 Times in 90 Posts
Default

Quote:
Originally Posted by ddahlgren View Post
Air 0.0765 lb/(cu ft)) according to ISA (International Standard Atmosphere).
times 100 is 7.65 lbs. Mr Vizard as usual is wrong again. It is a long reach to 38 tons

https://www.thoughtco.com/density-of-air-at-stp-607546
I misquoted him. His article describes a 100ft cube of air weighing 38 tons vs the 100cu/ft I posted. That's (100x100x100x.0765)/2000...which does equal 38.25 tons.

It's kind of mind-boggling....to me.
GREGGPENN is online now   Reply With Quote
Old 12-27-2017, 05:10 AM   #52
GREGGPENN
CF Senior Member
 
GREGGPENN's Avatar
 
Member Since: Nov 2003
Location: Overland Park Kansas
Posts: 11,007
Thanked 93 Times in 90 Posts
Default

Quote:
Originally Posted by Tom400CFI View Post
I think what the Corvette needs the most is more BENDS in the system, to reduce that hummmm noise that is made by the even firing of 8 cylinders. Just a theory though...
On the surface, I don't agree with that either. My sidepipes...with their 360-deg worth of bends contain as much/more bends than the clip above. The drone is less evident sans muffler...than with. It doesn't match your theory. Plus, tuned port (bass) systems often use ports with bends in them...for space. Nothing I've read indicates a change in tuning/efficiency.

That said, I understand your thinking...if you think sound waves diminish with directional changes. I'd have to look that up.
GREGGPENN is online now   Reply With Quote
Old 12-27-2017, 10:47 AM   #53
Tom400CFI
CF Senior Member
 
Tom400CFI's Avatar
 
Member Since: Aug 2004
Location: Park City Utah
Posts: 11,791
Thanked 379 Times in 341 Posts
Default

Quote:
Originally Posted by GREGGPENN View Post
On the surface, I don't agree with that either. My sidepipes...with their 360-deg worth of bends contain as much/more bends than the clip above. The drone is less evident sans muffler...than with. It doesn't match your theory. Plus, tuned port (bass) systems often use ports with bends in them...for space. Nothing I've read indicates a change in tuning/efficiency.
I don't understand what you're saying here. I didn't mention anything about efficiency w/regard to bent pipes, except to agree with 69427 that bends do reduce flow/efficiency of air movement in the pipe. I don't think it's very meaningful, but it's true.

With the Kart, it started off w/the factory Y and I stuffed a big magnaflow muff on then end of the Y that terminated just ahead of the diff. I did this for no other reason than to quiet it down b/c it was SO loud with just the ope Y pipe....too loud for driving around my neighborhood. Anyway, with the factory Y, with or without the muff, it sounded like a typical 'Vette with that "Hummm-y" sound 'Vettes make combined with some "V8 pulse" sound. But it sounded rather shitty. I didn't care b/c I knew I'd be changing it. I did change it and now it sounds radically different. The "hummm-y" drone of 8 cylinders is mitigated and replaced by that nice, "Mustang 5.0 burble". I wish I had done a "before vid" for comparison, but I didn't think to record it simply b/c it sounded lame; not worth recording.
Tom400CFI is offline   Reply With Quote
Old 12-27-2017, 02:11 PM   #54
84 4+3
CF Senior Member
 
Member Since: Aug 2017
Location: New Jersey
Posts: 146
Thanks: 0
Thanked 14 Times in 14 Posts
Default

Having the extra bends in my mind would introduce high and low pressure pockets around them which would increase turbulence and in effect induce mixing. With that extra mixing you are interrupting the some what smooth flow of the exhaust gas that is present and introducing more of a pulsing exhaust. Hence the burbley sound vs smooth. Also depending on where the bends are you can also introduce a resonant tuning effect in theory. All a muffler is is a series of directional changes and expansions/contractions. Reading through most of this has been said already though so sorry to repeat information.

In school we modeled different types of bends for pressure drops and short of using a straight 90 elbow, nice sweeping 90s that are mandrel bent don't offer that much resistance to flow on pressure driven systems. On something like a furnace that's a different story but I would guess an exhaust system is a pressure driven system or can be approximated by one. (This is just my experience so you all don't think I'm pulling this out of air lol.)
84 4+3 is online now   Reply With Quote
Old 12-27-2017, 02:55 PM   #55
Kingtal0n
CF Senior Member
 
Kingtal0n's Avatar
 
Member Since: Oct 2007
Location: miami florida
Posts: 204
Thanked 10 Times in 7 Posts
Default

with a turbocharger:

If I am on a budget build I throw a cheap resonator, muffler into the mix then test it.

If there is drone or problems with the sound, I would add a test J-pipe, or change the length of the system a little bit if possible. Or even add an extra muffler. The reason all of this works in the end is because no matter how restrictive the system is, you can always add a cut-out for max turbine differential.

I don't feel like I am so much tuning out the sound this way, so much as moving it to an RPM range where I don't notice it as much.


---
High performance N/A requires testing. Even if we calculate the sound pulse in feet/second and compare with RPM just so it is leaving the exhaust valve at the correct moment- it will still need be "dialed in" on a dyno of some kind, because small unaccounted for variables in the system can dramatically move the relationship of exhaust acoustics as rpm is changing, even in different gears. Remember each gear is a variable with respect to rate of change of engine RPM, so each gear will have a set of "moving" differentials depending on the acceleration of the engine. Which brings the issue of part throttle acceleration, where total flow is cut down by a percentage that will have an overall effect on exhaust gas velocity, favoring smaller diameter pipes, etc...
Kingtal0n is offline   Reply With Quote
Old 12-27-2017, 06:47 PM   #56
eutu1984
CF Senior Member
Support Corvetteforum!
 
eutu1984's Avatar
 
Member Since: Jul 2009
Location: Ashland PA
Posts: 937
Thanked 29 Times in 29 Posts
Default

Quote:
Originally Posted by 69427 View Post
Here's my H pipe. Connects the two collector reducers at the front of the pipes leading to my Y pipe at the back of the transmission. The crossover is removable by undoing the band clamp at the RH collector side, and then rotating/ pulling the crossover off if needed.




Made a significant reduction in drone, and according to Vizard the crossover here is usually worth about 3-5 horsepower improvement. A worthwhile endeavor, IMO, at only a pound and a half weight penalty.
unlike your C3 I dont think you would be able to put in a cross over H pipe on a C4 corvette due to ground clearance issues.

Last edited by eutu1984; 12-27-2017 at 06:48 PM.
eutu1984 is offline   Reply With Quote
Old 12-27-2017, 10:11 PM   #57
69427
Tech Contributor
 
69427's Avatar
 
Member Since: Jun 2004
Location: I tend to be leery of any guy who doesn't own either a chainsaw or a handgun.
Posts: 10,584
Thanked 124 Times in 107 Posts
Default

Quote:
Originally Posted by eutu1984 View Post
unlike your C3 I dont think you would be able to put in a cross over H pipe on a C4 corvette due to ground clearance issues.
Well, I don't know. I do know that my '69 is lowered substantially to improve the c/g location and aero lift reduction, and looking at my '84 I don't believe it's any lower than the '69. I did hold a 2 1/2" piece of exhaust pipe in the same crossover location (as on the '69) on the '84. Looks like it would package similarly to the '69.

I've got a turbo on my '84, so my exhaust system there is configured very differently than the '69.
69427 is offline   Reply With Quote
Old 12-28-2017, 07:03 PM   #58
GREGGPENN
CF Senior Member
 
GREGGPENN's Avatar
 
Member Since: Nov 2003
Location: Overland Park Kansas
Posts: 11,007
Thanked 93 Times in 90 Posts
Default

Quote:
Originally Posted by Tom400CFI View Post
I don't understand what you're saying here. I didn't mention anything about efficiency w/regard to bent pipes, except to agree with 69427 that bends do reduce flow/efficiency of air movement in the pipe. I don't think it's very meaningful, but it's true.
"Efficiency" referred to sound (not power) in my prior post. Basically, I'm saying my curvy-azz system -- which has WAY more bends than the sidepipe setup I see in your Kart build -- does not bear out your hypothesis. It had lots of drone with a belly muffler (then with a converter) in front of 360-degrees worth of bends. What I see in your "Kart" is nothing compared to the bends in SideEffects.

I'd bet big money that those Chrysler mufflers are the reason your system sounds great now. I may never buy an oval/box muffler again. I think bullet cats, glass packs, bullet mufflers, resonators, and/or cylindrical mufflers are the way to go. Now that I think about it, they probably serve as a mid-range/bass attenuator. Low frequencies travel in all directions while higher ones are more directional. Glass packs and Corsas have a LOW BIG sound but they also have a high, raspy bark. They both are missing the mid-bass drone. With the mid-bass present, the sound can be more dastardly -- but with drone. To me, the Corsa/glass-pack sound retains good-old USA...with a hint of smaller-cylinder (Euro?) finesse. Removing the mid-bass frequency does that IMO. And, that is what the mufflers you installed accomplish.

I submit that high frequency sounds remain by traveling straight through cylindrical shaped exhaust components. Plus, a portion of the low-frequencies travel straight through as well. As with bass cabinet (speakers) lined with fiberglass batting, omni-directional bass frequencies are absorbed by attenuating their tendency to bounce around inside the cabinet. (The batting actually slows low frequencies making the box seem bigger than it is. And...the more batting, the slower the waves).

In oval, rectangular, baffled, or box mufflers, little-to-no packing exists. The only thing managing sound is how pressure waves "bounce" around in the box. While I'm certain exhaust companies look to optimize HP performance, they also have to market with sound. Magnaflow and Corsa are examples where sound rates as high as power. Flowmaster is an example where sound is less important...or is marketed to owners who may LIKE boomy exhaust. In these large-bodied mufflers, bass can bounce and reverb into itself -- creating nastier mid-bass reverb. It's not a clean sound. It's not representative of what the motor is actually doing. To me, they are like a bass-ported speaker where boom is more important that image.

That's what I'm saying.

If you want to quiet an exhaust, my theory is to stay away from large body exhaust components. If you use them, they better be internally designed to dampen bass frequencies...like Corsas or stock mufflers. Expensive, factory mufflers use redirection, baffling, chambers, and batting to completely eliminate bass frequency. "Sport" mufflers try to control how bass bounces around in a box....And, I don't think they do a great job of it. They might not be able to -- simply because they don't allow ANY direct transmission of bass frequencies. Corsas don't have much/any bass at all (to me). They are like a stereo system with 6" woofers. They bark and are nasty but they don't RUMBLE.

That's why straight pipes and/or cylindrical components sound better. There's still a straight-line transmission of the lowest bass frequencies....and the highest ones. You get the rumble AND the definition of sound.

As for "H" pipes or "Y" pipes, merging the pulses SMOOTHS what you hear. The rhythm is doubled from each pipe making it more like a constant tone vs pulsing. In everything but an idle, tone is mostly what you hear. Also, H/Y pipes can increase the volume (mass) of the system. That changes pipes...and possibly drone. In some older cars, they even added weights to the pipes to dampen the pipes themselves. In the past, I considered trying this to see what happens. Fortunately, that box muffler rusted and I did what I (now) tell others. Try a system with the minimum of components before adding mufflers. If you want sound dampening, start with converters. They help your nose and perform similarly to cylindrical mufflers. They attenuate "boom". If still unhappy, add resonators and/or cylindrical mufflers until you are happy. The exception would be for the person who really likes the Corsa sound and has the money to spend on it. Personally, I think straight-through mufflers sound better.
GREGGPENN is online now   Reply With Quote
Old 12-28-2017, 07:40 PM   #59
Tom400CFI
CF Senior Member
 
Tom400CFI's Avatar
 
Member Since: Aug 2004
Location: Park City Utah
Posts: 11,791
Thanked 379 Times in 341 Posts
Default

Quote:
Originally Posted by GREGGPENN View Post
I'd bet big money that those Chrysler mufflers are the reason your system sounds great now.
I wouldn't bet that money. The Chysler muffs are the same shape (round), design and philosophy as the one I had on there before that sounded like poo; a straight through, perforated tube, glass pack style muffler.

I had that same style on my C6 too, when I had the GHL system on it. Poo and drone.

Now that Trans Am in the vid above...oval housing, straight through, perforated tube, glass packed...that thing sounds good. I had that same muff on my own TA and no drone. But look at the number of bends in the 3rd gen system! Yikes.

I can't prove anything here...but consider this:

In my C6 days, I tried all kinds of "cat back" exhausts on the thing and none of them really made any diff in the sound (or the drone). What I didn't change, was the configuration of the piping -it was always made up of mostly straight sections w/a few bends.


Now with the Kart, the diff in the Kart exhaust now and earlier is pretty minimal; stock Y to a 2.75" round, straight thru, perforated tube, glass pack style muff. Poo.

Now it's a bendy Y into two, 2.25", round, straight thru, perforated tube, glass pack style muffs, then more bends to the side pipe tips. Music.

What changed? I added bends and separated the sides.
Tom400CFI is offline   Reply With Quote
Old 12-28-2017, 08:15 PM   #60
billschroeder5842
ZenVette Master level VII
Support Corvetteforum!
 
billschroeder5842's Avatar
 
Member Since: Mar 2016
Location: Southlake, TX
Posts: 2,358
Thanked 264 Times in 238 Posts
Default

Quote:
Originally Posted by GREGGPENN View Post
If you want to quiet an exhaust, my theory is to stay away from large body exhaust components. If you use them, they better be internally designed to dampen bass frequencies...like Corsas or stock mufflers.
billschroeder5842 is online now   Reply With Quote
Go Back   CorvetteForum - Chevrolet Corvette Forum Discussion >
Reload this Page
  • Exhaust Drone!
  •  
     
    Reply

    Related Topics
    Thread Thread Starter Forum Replies Last Post
    Drone on CP C7 General Discussion 2 04-27-2017 08:59 AM
    C6 Exhaust fletchsd C6 Corvette General Discussion 3 03-09-2017 12:20 PM
    Any way to reduce drone? Roothog69 C6 Corvette General Discussion 49 01-09-2017 01:09 AM
    2007 A6 SLP 2 / kooks headers DRONE! TOPAZ1+ C6 Corvette General Discussion 5 11-16-2016 09:57 PM
    Exhaust Drone Question CharlieC5Z06 C5 Tech 25 03-26-2016 10:47 PM


    Thread Tools Search this Thread
    Search this Thread:

    Click for Advanced Search

    Posting Rules
    You may not post new threads
    You may not post replies
    You may not post attachments
    You may not edit your posts

    BB code is On
    Smilies are On
    [IMG] code is On
    HTML code is Off
    Trackbacks are Off
    Pingbacks are Off
    Refbacks are Off

    Forum Jump

    Sponsored Ads
    Vendor Directory

    All times are GMT -4. The time now is 04:18 PM.


    We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
     
    • Ask a Question
      Get answers from community experts
    Question Title:
    Description:
    Your question will be posted in: