Anything in particular that I should be on the lookout for? My admittedly limited understanding is that a straight-through perforated glasspack would not be very restrictive (vs a louvered design where the fins create turbulence). I am going off the very general rule of 1" diameter pipe per 100 hp. With four 2" pipes all the way through, that's 800 HP. Basically, it's 2" diameter for only 3 cylinders (12-into-4) – which should afford at least a little restriction (lowered velocity) before becoming an issue. I'd be a bit more concerned if it was 12-into-2 at 2" (400 HP); which is the typical setup. Very open to comments though.
Some car magazines in the past did research on performance mufflers. I believe if you do a little search on the internet, you will get some answers.
Why not ask Fabio if he is interested in doing a system for you? Design and construction of complete and customized stainless steel
I had heard the name before, but wasn't familiar with his work. Looks really nice though. He even uses some 3D printed parts in his projects. I also like the use of modern heat shielding; which I was thinking of adding to my manifolds as I'm getting really tired of replacing CV boots. Looks like he actually did a full Boxer exhaust about a year ago where he reworked the primaries (equal length?). I'd be very interested to hear how it sounds, as it's a very different approach than I am going. His website claims that this design is made to sound "like the older F1 12 boxer". To my knowledge, Ferrari was not collecting like this until after the 312 T5 was retired. So I think I am sticking to my belief that if you want that old school sound, you need 12-into-4. Image Unavailable, Please Login
Basically, yes. SLM uses a fine powder, with a laser that "welds" each layer before the bed lowers for the next layer. It really shines for complex shapes (eg, collectors). You could argue that tubing is a silly use-case for tubing, but the price has come down quite a bit and I like the exactness of it – plus the ability to reprint the exact same part if I want to switch to Titanium (or Inconel). The aluminum intake manifolds I designed for my EFI/ITB conversion worked the same way. The final part looks closer to cast than CNC (no drill bit paths). The plastic 3D printing I do at home is FDM, which is more like a hot glue gun attached to a CNC router. Same idea of doing things in layers and shifting the bed down after each layer is printed though. I've only done this a few times now, but my workflow is usually to 3D scan the area, design the part in Fusion 360, print the prototypes in plastic, then have the final part made in metal.
My son is an engineer, works for Lincoln Electric in Euclid Oh. He is a project manager in the laser welding dept. He tells me about the incredible process. Myself retired machinist, I just know how to cut metal, and weld.
Status update. I received the muffler tree bracket (my word for it) from SendCutSend. The shock mount brackets should arrive later this week. Image Unavailable, Please Login I mounted straight pipes in the muffler area, which allowed me to confirm fitment of all the various pre and post routing and that the tips exit in the right spot. I ended up going away from the mini megaphone tips. It just didn't look right. Instead, I went for a 2.5" straight tip with an inner rolled edge, and minimal protrusion. Because of the modularity in the design, I can always try different exits / tip designs. Image Unavailable, Please Login With the prototype plastic parts in place and everything double checked, I pulled the trigger and sent the designs off to be printed in stainless steel – which should arrive around Dec 16. I also ordered four Vibrant stainless steel glasspacks (essentially a better made version of the old cherry bomb). So there probably won't be much to report between now and late December, but I'll certainly post once the parts arrive. Hopefully everything fits, and I can run the car on a custom / modular 3D printed exhaust.
If you end up making manifolds I would focus on number 6 and 7 primaries. Thats where the cork is. The LM manifolds addressed this and cooking the CV boots is another issue. I considered making what the 360's use to protect the inner boots.
I've been looking into the heat issue a little bit. I think a common application is a ceramic wool ("superwool"), with a dimpled foil (sometimes welded for a custom fitment). A few companies I came across: https://funkmotorsport.com/product-category/heat-management/heat-barriers/ https://www.goodfabs.com/exhaust-heat-shield-insulation https://www.designengineering.com/products/heat-control/ https://www.heatshieldproducts.com/heatshield-armor-kit https://turbosource.com/pages/inconel-custom-made-heat-shielding-ordering-form Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
Stainless steel sheet, makes a good heat insulator. We put that against caliper pistons in race cars. SS is a poor conductor of heat.
I have some experience in what you're doing. I'd avoid 3D metal printed joints as much as possible. It's not cost effective at best and at worst the chance of sintered stainless cracking under heat cycles with dissimilar metals is too high. It's stainless, it walks all over the place with heat. Two options: 1. Ace Race Parts (No affiliation) sells SS precuts in whatevvvver diameters you are trying to use at any radius. They come pre-cleaned and washed, seamless, ready to weld. The headers below are this method, although I could've been smarter about a few of my primaries. These headers are about $600 in material. 2. Mandrel-bent CNC is the technically correct way, but convincing a shop to do short runs can be a challenge- if you could get 5 like minded people to join you in wanting one, you'd be money ahead of even pre-cuts when it came to labor- this would also allow you to do slip fit joints for future disassembly.
I was able to locate an archive thread started in 2007 by Paul Newman. I have reposted the link in case you havent seen it. My post is below with some details regarding the mini SS resonators Vibrant offered at the time. There is also a photo of the modified Borla system below. Hopefully there is something in here you can use. https://www.ferrarichat.com/forum/threads/boxer-exhaust-project.164577/page-2 Oct 18, 2007 Last edited by a moderator: Sep 7, 2017 The Borla exhaust system for my BBI will get a modification with lightweight 304SS mini resonators. The four 21" long over silenced original 1-3/4" core resonators are being replaced with (4) Vibrant 12" 304SS units from http://thmotorsports.com/vibrant/1790/1790/i-37707.aspx. These are their smallest standard SS resonators with a 2-1/4" ID. X 7-3/4" long perforated core. Reasonably priced at $41 ea. The four units will go to the weld shop this weekend to have straight pipe & flanges welded. I hope to have it assembled and on the car next week. Dave Found this Youtube Flyby taken from a friends car window.
Thanks Dave. That thread (and your videos) played a big part in confirming my suspicions that a quad exhaust was the sound I was looking for. So maybe you're to blame for me spending all this time and money replacing my perfectly good Nouvalari exhaust! I actually purchased those same Vibrant resonators. Attached is a pic comparing the Vibrant to the traditional cherry-bomb. It seems the Vibrant is basically a cherry-bomb in a tuxedo. Stainless steel, better welds, more accurate dimensions – just better all around. Image Unavailable, Please Login I also purchase these Porter "shorty mufflers" in 2" ID (same as the Vibrant and cherry-bombs). They have a lower tone that I am curious to try out. My design allows for easy swapping of mufflers, allowing me to experiment until I find that perfect sound. Image Unavailable, Please Login Funny enough, I found a guy on YouTube who tried both and did a pretty good job recording them. Glasspacks Porter shorties
That's interesting. I'll have to look more into that. I've seen reports of SLM being used for stainless and Inconel manifolds / exhausts without any mention of cracking, but maybe I just wasn't looking hard enough. The combination of the rubber shock mounts and the "tree" design will hopefully minimize stress. It wasn't until I mounted the prototype that I realized the benefit of having each of the mufflers kind of floating. Curious if this actually helps. I designed the exhaust to use standard bend radiuses instead of more organic bends as a Plan B in the event that I need to have it cut / welded instead of printed. Hopefully it doesn't come to that though.
Absolutely can be. Manifolds all day long, no problem. Hell, we've been using cast manifolds for 100 years, but a full system has to be engineered really, really well. Drawn stainless tube is better for your application in every single way, in my opinion. Surface finish- Drawn seamless tubing will have much better flow, any finished stainless should come in around 8 Ra, where 3D printed is going to be 11-15 ra. Do some flow calcs and see if it makes a difference for your application- remember bigger tube isn't always better. Cost: I'm genuinely curious about the quotes you've gotten back for the parts you need- I've owned metal 3D printers in the past and I know what they cost to run. Nothing about your design seems to be taking advantage of the fact your 3D printing it. Toss in some gussets on the corners, mess around in Flow sim to create rifleing throughout the primaries to increase scavenging. I know SLM loves to say they make a "finished part right off a printer" but please please stress relieve these parts. There's not a FEA package in the world that can accurately know what engine and chassis harmonics are going to do. Failure rate on any part on a long enough timeframe is never zero just from sheer entropy. I think your design is going to sound great, and the floating mufflers are good for stress. Good call. Whoops realized I never attached the picture on my last post. Image Unavailable, Please Login
Ah Wesley, I've been following your M120 progress on YouTube! You posted your ITB video right as I was in the thick of my EFI/ITB conversion. It was actually my ITB conversion where I first used SLM for custom intake manifolds. I've used it for aluminum a few more times since, without any issues. This is my first time trying SS though. It's mostly a curiosity. I feel like you of all people would appreciate the "let's see what happens" approach – especially since a cracked exhaust pipe isn't exactly likely to have upstream catastrophic affects. I am using CraftCloud for the actual SLM (SendCutSend for the sheet metal components, like the "muffler tree" and the shock mounts). I've looked into other services (Xometry, Protolabs, etc.), but CraftCloud has often been much cheaper. So cheap, that I was concerned it was a scam the first time, but my parts arrived on time and in spec (see my ITB thread; which includes the cost estimate for the manifolds). Included is the cost estimate for the post-muffler section. It hasn't arrived yet, so I can't yet speak to the surface finish, fitment, etc.. If it's anything like the aluminum parts I've had made, it's usually a bit rough. Essentially like a cast part. There are few shops around me that I think can do this work the conventional way, and to a high level. I haven't yet gotten a cost estimate yet though, so I can't say for certain how it compares. Image Unavailable, Please Login
If anyone's curious, one notable example I found of a full 3D printed exhaust was the "Half11" car; which uses Inconel. Here's a quick snippet of the builder talking about it (skip to 3:14): There are other examples too (eg, Harley Davidson racing), including use in F1. Sometimes it's just a collector, other times it's long stretches of complex geometry. In my case, even though I'm not using complex geometry, the benefit is the ability to reprint in various metals, and experiment with the modularity of it. Basically, if I have this made conventionally, I'll feel like it's a one-and-done; which I don't want. I want to iterate and experiment. That said, I'm very open to concerns / warnings / anecdotes, etc.. I'm just offering counterpoint examples.
