S54 Header Design talk

[3staxontheradio]

Looking at how craftcloud prices with their auto quote system. First test is for finding maximum dimensions before the price jumps up. There is a hard jump somewhere between 300 and 375mm and I assume that has to do with needing a bigger machine:



More interesting is how it handles multiple units of the same part and ordering volume. For this I made 3 nearly identical elbows, files are all slightly different. Pricing doesn't seem to care about 10 units of the exact same part vs 10 units of a mix of similar parts. It does give a large discount for quantity.





Tomorrow I want to test some complicated shapes and compare bounding volume, material volume, and how much something impacts packing space in the machine. I'm expecting parts that pack easily to be cheaper than those that would eat up more space in the machine or be harder to pack efficiently.

[3staxontheradio]

Quick testing on how packing efficiency impacts pricing and it doesn't really seem to in any meaningful way. I'm sure there is some minimum scale at which a negative space is considered not pack-able by their software but it's probably a smaller scale than matters for anyone making car parts.

Both of these tests the two models have exactly the same total volume they are just laid out a little differently so they take up a bigger bounding box or become harder to densely pack into a build volume. This is good to know because it means bendy primaries aren't any cheaper by cutting them up more times to keep straighter runs. There might be support material reasons to try to do that but its at least not a cost concern:

[3staxontheradio]

I think this is how I'm going to lay out the exhaust. The merges are so much further down the line which shifts back a bit compared to what people are used to. This X pipe location is on the second order harmonic for 4900 rpm which is where the factory puts the H. Also stepping from 55mm factory collector diameter up to 2.5" exhaust at the 4th harmonic which should also generate a wave that hits at 4900 rpm. The transition to 2.5" tube is dead on equal length and then X cross is very close, within maybe 20mm. Total exhaust length is also very close. This should all sound very good and perfectly in time between banks and at every wave,splitting event.

[Bry5on]

I think that you’re right that ditching the factory header flange location makes sense. I think this is why I was struggling so much to pack everything.

Would it make sense to target a different harmonic for the 55-63.5mm step up? Or is it advantageous to stack all of the harmonics at a single rpm? Thinking maybe you’d want to move this closer to 7krpm if you could to broaden the curve benefits.

Now you’ve got me thinking about making a full section 2 with a better/shielded cat setup for the HJS cats. Hadn’t considered downstream of the headers printed parts. Are you running catless?

[3staxontheradio]

I think that you’re right that ditching the factory header flange location makes sense. I think this is why I was struggling so much to pack everything.

Would it make sense to target a different harmonic for the 55-63.5mm step up? Or is it advantageous to stack all of the harmonics at a single rpm? Thinking maybe you’d want to move this closer to 7krpm if you could to broaden the curve benefits.

Now you’ve got me thinking about making a full section 2 with a better/shielded cat setup for the HJS cats. Hadn’t considered downstream of the headers printed parts. Are you running catless?

I'm not sure about stacking harmonics vs spreading them out. Sort of by mistake the two collector harmonics are slightly spread with the X pipe hitting slightly higher rpm. I'm very curious to see where there might be holes in the torque curve. Also my understanding based off of google reading is that H pipes tend to produce a bigger effect on the bottom end at the expense of high rpm flow and X pipes do better on the top end. Not sure how big that difference is though or if its going to matter here.


Yes catless for now. I'll probably sneak some cats in after doing all the dyno/power testing.

[George Hill]

Is there a particular reason to go catless from your data?

It seems they are so efficient nowadays is there really a downside other than cost?

[3staxontheradio]

It's one more place to spend money right now and another packaging problem to solve. The 2.5" cats I have here are probably slightly too big to fit side by side with this 100mm on center exhaust routing.

[George Hill]

Fair enough for your own project but personally I think if you don't make allocations for cats to fit, even at a later date, you are cutting out a large segment of potential buyers. IMO a guy who is into your kit for $5-6k isn't going to be stopped by $500-750 for cats.

[3staxontheradio]

Here are two possible locations for cats. A more typical middle position with the resonators swapped out for 12" versions and a position way far back where cats reducing velocity won't matter. They will take much longer to heat up in the back but should have the least impact. You could also just as easily move them to just in front of the resonators.

I'll update the exhaust and xpipe spacing to 104mm on center to fit 4" cats without any challenges.

[Vanar]

Any thoughts on z pipes?

[3staxontheradio]

Any thoughts on z pipes?

They look cool and probably sound pretty good in this engine since it can actually rev. I plan to test one in place of the x pipe and pick whichever sounds better or performs better. It's not a particularly hard part to model and it's not actually a new idea. It does seem really well suited for 3d printing since getting that complicated of a shape with traditional fabrication would be a ton of work and likely take up way more space.

Also the very limited youtube testing I have seen has been badly set up so it would be good to be able to compare and see what if any difference vs a good x pipe would look like with nothing else changed.

Also I do have a pretty high end portable audio recorder so whenever this is done I will get a lot of very clean audio.

[heinzboehmer]

Also the very limited youtube testing I have seen has been badly set up so it would be good to be able to compare and see what if any difference vs a good x pipe would look like with nothing else changed.

No Z pipe, but your comment made me think of this video: https://www.youtube.com/watch?v=mU3n_j_H8uQ

Probably the most apples to apples comparison I've seen for the setups shown.

[Vanar]

I’m pretty sure they’re only made by 3d printing, though not sure if I’m remembering correctly the borla crossfire may be different

[3staxontheradio]

People have been making versions of a zpipe for decades, it's not a new idea but zander guerra designed a printed one and popularized it. Borla makes a hydro formed version they call switch fire. I have seen people do it with normal welded bends and tube but it's bulky and hard to get the CSA consistent and also keep the flow paths equal length. The leg of each y that doesn't cross needs bends to make it equal length to the one that does. You can also buy knockoffs online for like $250 which is about what it would cost to model and print one on craftcloud. I'm planning to model my own so it can exactly fit into the space I have and match the distance between my exhaust at that point.

I think the patent pending status on the zpipe irksome. It already existed before he ever built one so the concept of my mixing exhaust banks this way isn't original- even if he wasn't aware of others when he came up with it. You don't see other people trying to patent existing Y, X, or H merges. My understanding is the patent claim is about using 3d printing to create an exhaust crossover that is different from an H or X pipe. I don't think he could get a patent without the 3d printing qualifier since there is prior art and its not new. Not a fan of taking something that already exists, changing the fabrication method, and then claiming a patent on that as if its an actual invention.

Here is a reference from dr gas talking about building Z pipes in the 80s. at 5:24:

[George Hill]

Dr. Gas, now there is a blast from the past. I had his X pipe on my TransAm in the early 2000s and it sounded incredible. Still have the X, but the design makes packaging it fairly complicated on any modern car. Thanks for the video!