I'm getting sick of trying to find the perfect mufflers and so forth so I may as well make my own. I have plenty of space, think of a 20"x12"x12" space for each one.

Now then, What do you look for in a muffler sound wise?

1. Dead quiet at cruise on the freeway?
2. All hell breaking loose under throttle and at higher RPM's?
3. What about at idle? Maybe have a switch for loud or quiet?
4. Have to be able to adjust just how loud - loud is for sure.
EDIT:
5. Stealth mode - always quiet
6. Show-off mode - always loud

I need ideas. Anyone know how the vette adjustable muffler works?
EDIT:
It sounds like I would need to use a vacuum operated lever to control a baffle or door. Under load the engine vacuum will drop and the door can open allowing the exhaust to bypass the "muffling" section. I will probably need to delay it as well.

What mufflers come close to the sound you want? I know the Borla Stingers kind of do it for me, but I can't find the 5" borla's sold seperately.

What are you thoughts?
Anyone have some ideas?

 

I'm not really sure much, I know I have some books on it, but some other people probbly know alot better then I.

Either way if you are really doing this I'm going to watch this thread.

Best of luck!

 

I've thought about making my own before also. Will be cool to see how it turns out.

 

Keep in mind my car is a 2 seater and I will be cutting out the rear floor pans and put these mufflers where the rear passengers feet would be. This is why I have so much room to play with. I'll also install tunnels under the front seats to keep the whole shebang tucked up high.

 

I thought about doing this, but it makes more sense to go with a stock muffler for dead silence freeway driving and use a cutout for full throttle. A vacuum operated switch would work well, but I decided against this because I wouldn't want it fully open everytime I open it up. Many days cruising through the city I give it full throttle but don't want to attract every cop at the same time, so the cutout lets you choose when you want it done. The vacuum idea is neat, but you'll still need a cutout to make it work, so its easier to just go with it and be done assuming its an electric version.

Far as mufflers are concerned, I almost did what you want to do because I couldn't find thin cheap good sounding mufflers for my true dual, and mufflers are pretty easy to make, you just have to decide on what design you want. I ended up not going that route when I found some slim mufflers for 15 bucks each that fit my needs perfectly. Since you want dead silence on the freeway I'd stay away from those open mufflers like flowmasters. You should make one that is square that way you can cut inside rooms to stop the sound and use plenty of deadner. Heres a video of one muffler open-this is the design I'd use for quiet sounds http://auto.howstuffworks.com/muffler.htm

 

That's a cool link, thanks. I just now decided to throw caution to the wind and make my own, so I haven't done much research on all the different designs.

I had a stock exhaust with a magnaflow muffler and a QTP right before the axle so I'm very familiar with them, but they have their drawbacks as well. One being they take too long to open and close. I also never really opened it part way. I would prefer having one that used a solenoid to flip it full open or full closed and do it very quickly. There's just no need for all that gearing, motor and billet housing stuff. It's just a waste of money. A spring loaded flap (in both directions) and a solenoid is all you really need. Still, I wouldn't want to have to keep messing with it to be loud most of the time and then have to flip a switch to make it quiet when cruising on the freeway. I mean, it's not a bad idea.

I'm going true duals, BTW, hence the need for 2 mufflers.

Should I exit the exhaust at the back of the car or dump it underneath? I wonder if a quiet exhaust dumped under the car would create drone?

I'm not into flowmasters, more like Magnaflow's and Borla's with their straight through design.

 

I also like the way Tubi gets the sound they do for Ferrari and Lamborghini. That high pitched whine, but that probably has to do with their small bore engine design. The Corsa muffler for the vette is sweet as well, but not their f-body muffler.

I wonder if anyone has used a 7" round body Magnaflow desiel muffler (4" in/out) on a true dual setup? I bet that would absorb the low rumble and really let it scream at high RPM's.

http://www.magnaflow.com/02product/s...e=main&id=1068

 

After burning out a couple motors on my cutout, I modded it and added a door lock solenoid on it that instantly closed and opened it instead of the gearbox/motor. Worked out quite well

 

The door lock motors don't hold tension on it, does it?
Do you have any pics?

I found a pic of the vette muffler. That's pretty much how I thought of making mine.

 

You have a good point about sometimes wanting a "stealth" mode so it's never loud. While were at it, how about a "show-off" mode for when you around your friens and want it fully open and loud at all rpms and engine loads. I'll add these 2 to the list.

As for a needing a cutout, no, you don't have to waste 300 bucks for a pair of them. Something else can be made much more cheaply.

What mufflers did you end up using for $15 each?

 

As far as adjustable mufflers go, there is Supertrapp. I forgot all about Supertrapps adjustable mufflers. I see they also also have these cheaper disc setups that can be added to the end of the pipe to control the volume and flow.



http://store.summitracing.com/partde...5&autoview=sku

An idea I had years ago and kind of forgot about was taking a perforated core muffler like a magnaflow and making it ajustable. What you do is take a real quiet version like their 5x11x30 (or maybe smaller) and then slide a tube a hair smaller in diameter than the inner perfed tube and slide it into the muffler covering up some of the little holes. The more holes you cover the louder it will be. If you cover them all it will be like a straight pipe with no muffler so you have a wide range to play with. Once you get it adjusted to your liking you can tack weld the tube in place and add a removable turn down. This way you can adjust it later if you want to.



In reality their 5x8x18 or their 6" round would probably be a good starting point.

 

I've put a lot of thought into this and so far my best plan is to add some tunnels in the floor board under the front and rear seats to tuck the 3" pipe up high. I can have almost a straight shot from each header to the rear of the car and straight under the axle. Then have the pipe angle up and run a nice beefy perforated core muffler. I may be able to add an H pipe as well. The sound and overall volume level can then be adjusted by taking a sheet of stainless steel and rolling it up then sliding it in the muffler. When you release it, it will expand and cover the holes in the muffler core. The more holes you cover the louder it will be. I can fine tune it and this will be the quiet level. I'm sure it will have some muscle at higher rpm's, but if you keep the revs down it should be nice and quiet. At cruise speeds as well.

For the all out loud and raunchy sound I may have to install some electric cutouts (maybe something I can make myself) and mount them maybe in front of the axle. This may satisfy my initial list of wants, or at least come close. I still need to figure out what muffler to use. I need a 3" perfed core unit with a straight through shape. Magnaflows seem my best bet. Maybe their 5" or 6" round by 14" long body units. I think the larger diameter compared to a 4" will help reduce any droning sounds in the interior. I know their 6"x30" is too long to fit, but they also have a 6" round x 18" long. I might actually be able to fit the 30" long body if I have the muffler start just behind the axle and angle the end up to meet the Trans Am cutouts. It's a thought. It may look a lot like this:



Some nice and short tips will be the key to making it look good. If the mufflers work out well, I can have them polished.

 

Straight from GM's Service Information for an 07 ZO6/XLR-V. Just thought you might care to read it.

The Exhaust Flow Control (EFC) System enhances engine performance. The system has 2 modes of operation:

• Normal

• Competition


Normal Mode
When the vehicle is stationary with the engine running the exhaust flow control module (EFCM) commands the vacuum solenoid On, which supplies engine vacuum to both exhaust flow control valves. This causes the valves to close, diverting exhaust flow through a baffled path inside the mufflers. As vehicle speed increases, throttle position reaches 25 percent or greater and engine speed reaches 3500 RPM, the EFCM commands the vacuum solenoid off. This causes the valves to open, diverting exhaust flow through an un-baffled path inside the mufflers, thus enhancing engine performance.


Competition Mode
When traction control is driver disabled, vehicle speed increases, throttle position reaches 25 percent or greater and engine speed reaches 3000 RPM, the EFCM commands the vacuum solenoid off. This causes the valves to open; diverting exhaust flow through an un-baffled path inside the mufflers more frequently and at lower engine speeds.

The system also delays exhaust valve activity during wide-open throttle acceleration to inhibit exhaust valve actuation when the accelerator pedal is released and reapplied while shifting gears.

The EFCM has the ability to detect electrical malfunctions within the system. Any electrical malfunction detected will cause the system to be disabled and increased exhaust audibility.

The system uses the engine control module (ECM), body control module (BCM), electronic brake control module (EBCM), EFCM, exhaust flow control valve vacuum solenoid, vacuum reservoir, vacuum lines, 2 exhaust flow control valves and the serial data circuit to perform the system functions.

 

Wow, I knew it was electrically controlled, but had no idea it was so complex. Thanks for the info.

 

Yeah it's pretty cool. Let me know if you want anymore info, I'm a GM tech.

 

I'm confused. Are you planning on cutting the floorboard for the mufflers and pipes to mount high or just to be able to run the pipes up high in the floorboard? Sounds like a lot of work just to have the pipes tucked up high in the floorboard only to run them under the axle (lame IMO) and into mufflers under the bumper and still may not have enough room to run an H pipe. You can do all that and more with oval piping and not even have to cut the floorboard. And you can fit 2 good size mufflers under the gas tank with a little thought and patience like the first pic or if your set on cutting the underbody, do it in the trunk area like Mark did in the 2nd pic for full size mufflers. As far as making your own mufflers, I don't have a clue.

 

Nothings been set in stone. First off I can't use the area behind the axle as I'd like to relocate the gas tank. The only space I would have to use is the area right under the frame rails on the far left and right sides. I haven't decided on wether I will use 2 or 4 mufflers. Right now I'll cut the tunnels in the floor board to tuck up just the 3" exhaust piping. Maybe some folks can fit ovalized tubing under there, but I've already scraped the bottom floorboards so I plan to have the piping tucked all the way up so it won't get scraped.

I don't know why you don't like going under the axle, I think it's the coolest **** since slice bread. It looks really badass with polished mufflers. I won't even have to curve it down, the axle is so high it will go right under, plus I plan to reduce axle extension by 2" which will help.

I think I can run the magnaflow 6"x30" round mufflers in the back under the frame rails for my quiet system, plus I will have room in the rear passenger seat area for either twin cutouts or maybe some kind of mini muffler to use for when I want things loud. It's going to be trial and error as I don't know what it's going to sound like, yet.

As far as an H-pipe, I don't really care about it. People say it helps the sound so I was going to try and add it, but no big deal if I don't.

 

Don't know if these would even work, but there's always the Flowtech Warlocks . With an E-cutout on those, you may find them handy. They might be on the large size though.

 

Interesting, but I have no idea what they would sound like. Due to that it would be a risky choice.

I'm actually running into a small problem I hope someone can help me with. I realized that if I install the tunnels into the floor the hump would be real close to the electric motor on the drivers side seat and the air pump under the passengers seat. What can I do to keep these 2 pieces from getting too hot? Does Dynamat work as an insulator or should I cover the tunnels with joot insulation (what is under the carpet from the factory)? I'll probably have to slit the carpet open to allow for the tunnels.

Any suggestions?

Here's a pic of a under the axle dual exhaust with mufflers right under the frame rails on a camaro.

 

I think before I go cutting up the floor I'm going to try another design first. Since there is already an oversized hump on the passengers side I was thinking of making a single muffler that could handle the volume of dual 3" collectors. This cuts the work in half.

There is a space of about 9"x20"x3.5" for it to fit in. So I'm starting out with a box shape that has the 2 inlets and the outlet should be on the passenger side. I was thinking of making a wide, but thin outlet that would poke out the side, sort of like a NASCAR boomtube. Check this pic for the exhaust tip.


Now so far I'm working on a typical Flowmaster type style with a little bit of turbo or dual chamber design. Here's the orientaion:



And here's a few sketches I did.



Here's a blank pattern for anyone that has a suggestion. Just remember that once the pipes go in you have to have enough space for both engine banks to breath through one muffler so I can't have real small passages.


I have an old Magnaflow off my car that I can cut open and use some of the guts from if I want to add some packing or something, but right now I'm interested in how to get this unusual design to flow and create a unique sound. This is going to be on open headers as well. If I come up with a design that is really quiet then I can weld my electric cutout straight onto the muffler to make it louder when I want.

My basic plan is to weld up a box with a removable lid held on with screws. This way I can open it up and manipulate the insides to try different designs. The internal baffles and such can be tack welded for testing purposes right now. If I get something I like I can weld everything up solid. I'm not sure how to keep rust away, but if I make something I like I suppose I can have it Jethot coated inside and out or something. Anyway, your design ideas are welcome.