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I have this covered in my build thread already (https://www.thirdgen.org/forums/memb...ml#post6255173) but I thought I would also post this to the exhaust section for anyone looking for a more custom or DIY solution to exhaust systems. I'm not trying to reinvent the wheel and I'm not going to say that this is better than a mandrel bent exhaust with a Magnaflow muffler but it was around 1/4-1/5 of the price and it's exactly what I wanted to have. What I wanted to have was a fully stainless steel exhaust system with the best ground clearance that I could get and a muffler that did not scream "look at me!" every time I pressed the gas pedal.
I started the project by pricing stainless steel exhaust systems out.
$500 for over the axle back with a Magnaflow muffler so I'd still need to fabricate the forward section that would connect to the headers. https://www.hawksmotorsports.com/mag...-92-5-0l-5-7l/
I also started researching what the differences were between the mufflers like Spintech Vs Magnaflow Vs Flowmaster Vs Borla Vs traditional glass pack. That search brought me to the thought of "why don't I just make my own?" So I started looking into the designs of rebuildable mufflers and materials used in packing a muffler.
It's pretty easy to figure out how to make a muffler quieter: A longer length of acoustical material, a thicker body of acoustical material and a tube with more open area. Most of the mufflers I was finding were shorter with a resonator body of 12-18" long and when you wanted a body over 18" long it was usually considered a truck muffler and the body would become much wider. The perforated tube part of the muffler varied a bit; on cheap glass pack mufflers they basically used a cheese grater design.
On some the cheese grater would be toward the inside and others it would be toward the outside. On the Borla, Magnaflow and cheap eBay mufflers they used a true perforated tube but how open the perforations were and the amount of spacing between them also varied widely. Here is an example of mostly closed vs mostly open:
Some of them would only have an open area of (I'm guessing here) 25% while the Magnaflow looked to be up to high 40%. What I saw with Magnaflow and Borla was that their more open designs had slight turn or bump impeding to (I'm guessing again) cause more of the acoustics to be absorbed by the packing material. This is a Magnaflow muffler.
I decided on an exhaust pipe of 3", a muffler body that was 24" long with a width of 5". A perforated tube with an open area of 58%. One side of the muffler would have a removable top and the entrance side would have a V band flange for easy removal. So now I could start building the muffler.
For building the muffler I used my 3.0" stainless tubing, a 26" of 5.0" stainless tubing that was slightly expanded on both ends, a 24" long sheet of perforated stainless steel with an open area of 58%, a V band flange and a small sheet of 16 gauge stainless steel.
In the above picture you can see that I welded a short length of the 3.0" tubing to the V band flange, I think it was a 3-4" section. There will be 1" that sticks out of the muffler and 1" that sticks into the muffler. To make the end caps I used a 3.0" hole saw to make a hole the tubing could pass barely through and then I traced a 5" circle around the 3" circle and I cut those out of the stainless sheet. For the sides of my removable end caps I cut off the expanded ends of the 5.0" tube.
Then I just welded it up.
To make the perforated tube portion I had to use a piece of stainless perforated steel sheet and calculate the circumference of a 3.0" tube (~9.5") and add an inch for overlap (~10"). So cut a piece of material 24" x 10" and I wrapped it around a piece of 3" OD tubing for the middle and on the end I used the exact 3" stainless pipe I would use for the exhaust. I also cut a strip of stainless that was 3/4" wide and the same length as the tube I was making, 24". I made sure to leave some overlap of the ends and put the stainless strip under the overlapping ends. I next used simple radiator clamps to clamp the entire assembly together which took about a dozen clamps. You can see in the pictures I got everything to overlap and line up near perfect.
I had originally tried to use some thin TIG rod for stainless but it was requiring too much heat and I was melting the honeycomb so no dice. So I had to make a second assembly and this time I used TIG brazing rod for stainless and was able to TIG it up. I only broke through the honeycomb on one or two spots but it turned out pretty good with noticeable distortion.
For packing material I copied what Borla and Magnaflow use and I wrapped the perforated tube in an overlapping layer stainless steel wool first.
Followed by a layer of fiberglass:
The fiberglass I used is ceramic fiberglass that is rated to 2000°F so I have no fears of it burning or melting on me.
I then pushed the whole assembly together. The perforated tube slides over the 3.0" tube that is on the opposite side of the muffler body and it's sticking in an inch. It is a very tight fit as I had to smack it with a rubber mallet the last 1/3 of an inch. But I took it a step further and drilled the endcaps for rivets, this thing isn't coming apart by accident.
I bought 10' of 2.5" stainless tube (used 8') and 8' of 3.0" stainless tube (used 7'). Doing the entire length with pie cuts-- no pre-made bends or taking sections to the exhaust shop for bending. So 2.5" from each header into a Y just behind the transmission cross member and then a single 3" to the axle, over it and connecting to the repackable muffler I made. To make the bends I cut opposing 7° angles on a piece of tubing that is 1/2" wide at it's shortest point. Each angled section has to mate up with another section that is within 7° of the other section. If a pipe's cut is more than 7° different then it will not mate up well and you will have an underhang on one side and an overhang on another side. So a 90° cut will mat up with a 83°, 90° or 97° cut. Even though it seems small you can make some really tight turns with 7° cuts, much tighter than a bending machine can allow and the bends from a pie cut can be double curved instead of only single as a mandrel bend allows. Most people say to use 4.5° or 9° cuts but I found I like to just use 7° cuts and call it a day.
Yes, that is a Harbor Freight bandsaw and it has worked out perfect for me for multiple projects over the last 2 years. Cutting the 5" tubing did reveal a an angle of maybe 89° instead of 90° but that could just be from the feed rate or blade dulling.
I also made the Y portion of the exhaust myself and it was easier than I thought it would be. I decided to have the passenger side portion straight and the driver's side portion angle into it. I eyeballed (conservatively) about where and how I needed the driver's side tube cut and cut it in the bandsaw. I checked the fitment and just slowly took more out with a cutoff disk and then rounded it out with a carbide bit. Fits up pretty good. The tubes from the headers are 2.5" and the merge pipe is 3.0". I just crushed the 3.0" pipe down to 2.5" in the X dimension and it fit pretty well.
Here is the Y portion welded together
The inside took me some time because I forgot to remove the overlapping section before I welded it in place but it turned out fine IMO.
Everything from the Y pipe up welded together.
Proceeded to work on the middle portion which obviously went much faster.
Here is the entire section up to the axle welded together
I made my own exhaust hangars using a 1/8" carbon steel plate and a bent piece of 3/8" stainless steel. I used some 309L filler rod to weld the two dissimilar metals together.
My stainless steel welding was also really improving by the end of this
And here is a rear shot showing the muffler in place with a slight turn down on it
Overall I'm very happy with it. It really is much quieter than the old glass pack muffler I had on there and it seems quieter than my neighbors stock 2000 4.6L Mustang GT with a Flowmaster. It has has a deep sound to it, absent is that higher pitched cackle that you hear out of some glasspacks that I was afraid I might get. I'm hoping to find someone with a Magnaflow at a car show that I compare sound to. Anyway, this is what I did and I wanted to share in case anybody was looking into how they might try and do something.
awesome job man, you can always use mig wire for tig filler when dealing with thin material and low amperage.
I used 0.045" 308L filler rod for the tubing with a max amperage of mid-50s and 1/16" 308L filler rod for the V band flanges with a max amperage of 100 on a pulse setting with 30% on time and 15% background at 2 PPS. Worked great for me.
Very nice Tibo. When I first started reading this I thought to myself, "Who is crazy enough to do something like this but me?"
Then I read the name - Tibo. I shoulda known. I mean that in a good way. All done with 7 degree pie cuts - impressive.
And thanks for that info. All of that stainless could not have been cheap.
My future project is a "catalytic muffler" - a stainless steel glasspack style muffler inside a real catalytic converter case (cat is 3" IN & OUT, oval case). A 24" piece of 4" stainless pipe cost me $70.00 alone.
My car has the full SLP 1 5/8" headers single 3" cat system. Even though I don't have to pass CT emissions anymore, I want it to look like I still have the converter in place. My goal with this is to take some of the bark out of the system without adding any restriction. The cat converter case is not thick enough to use perforated pipe inside the full 360 degrees around. So I will have to drill holes on the sides only and perforate it myself. I plan to use stainless steel scrubber pads between the outside of the 4" pipe and the case. Inside of the 4" pipe will be a SS spiral auger insert - the center tube is 1.5". I'm hoping this will break up the sound wave to make the car quieter, without hurting the flow. A portion of the exhaust will flow straight through the 1.5" pipe. The rest will take the longer path around the spirals, being dampened along the way by the holes in the 4" pipe and SS scrubber pads. The 2 exhaust streams will join back together at the exit end, and then to the SS transverse muffler at the back of the car.
Don't be surprised if those rivets do not hold. I have blown up the SLP transverse mounted SS muffler all the way at the back of the car in the past. And a working cat converter was in there at the time. That was with the 305 engine.
Last edited by NoEmissions84TA; 12-08-2018 at 09:25 PM.
Really nice work Tibo, you are a true craftsman with some mad welding skills. You think about maybe putting a flange on one end and selling these?
I could but I would have to charge at least $200 to make it worth my time. The materials alone cost as much as a new Magnaflow so I would think that would deter most people. I have a V band flange on one end already too.
Just from YouTube clips it sounds similar to a Magnaflow muffler. Quieter than a Glasspack and Flowmaster. Definitely no longer worthy of a loud exhaust ticket. Sometime this winter I'll try to get my hands on a decibel meter. I've tried the phone apps but they are horrible for measuring anything louder than talking or background noise.
A 24" piece of 4" stainless pipe cost me $70.00 alone.
Just depends on what series stainless it is. 409 series is usually cheaper, it's ferritic stainless and has less corrosion resistance than 304 but if we aren't driving the cars in the winter months with salty roads I doubt we would be able to appreciate the difference.
Originally Posted by NoEmissions84TA
My future project is a "catalytic muffler" - a stainless steel glasspack style muffler inside a real catalytic converter case (cat is 3" IN & OUT, oval case).
My car has the full SLP 1 5/8" headers single 3" cat system. Even though I don't have to pass CT emissions anymore, I want it to look like I still have the converter in place. My goal with this is to take some of the bark out of the system without adding any restriction. The cat converter case is not thick enough to use perforated pipe inside the full 360 degrees around. So I will have to drill holes on the sides only and perforate it myself. I plan to use stainless steel scrubber pads between the outside of the 4" pipe and the case. Inside of the 4" pipe will be a SS spiral auger insert - the center tube is 1.5". I'm hoping this will break up the sound wave to make the car quieter, without hurting the flow. A portion of the exhaust will flow straight through the 1.5" pipe. The rest will take the longer path around the spirals, being dampened along the way by the holes in the 4" pipe and SS scrubber pads. The 2 exhaust streams will join back together at the exit end, and then to the SS transverse muffler at the back of the car.
If that's something you want to try and you want a project- go for it. My thought is why not just run one of the "High-Flo" catalytic converters? You can buy them fairly inexpensively now. I actually bought two high flow cats in 2.5" for about $70 each. I may still use them. I bought them because cold starts on this engine definitely release a gassy smell. I'm hoping most of it can be tuned out since it's just now cold enough to work on the cold starts, I've already scaled back on the amount of warm-up enrichment I was using.
If that's something you want to try and you want a project- go for it. My thought is why not just run one of the "High-Flo" catalytic converters? You can buy them fairly inexpensively now.
The money is already spent. All that's left is to actually do it. It is an experiment. I want to see if the spiral auger will bust up the sound wave and work against itself to cancel out some of the noise. I realize it will probably only work within a certain rpm range, but that is why we do the experimenting in the first place. Will it be a great success, a huge failure, something in-between, or just a complete waste of time? We shall see.
12-08-2018, 12:10 PM
All done with 7 degree pie cuts - impressive.
