S54 Header Design talk

[3staxontheradio]

Does anyone have any information on what effects can be expected from noncircular exhaust runner cross sections? As in if you were to flow from a round profile to a D or triangular shaped profile, while maintaining cross sectional area, and avoiding any sudden transitions, can you assume the runner would behave like an equivalent round cross section? I would think that if cross sections can be non-circular, then lots of interesting things could be done regarding packaging and weight saving.

This is one of the things I really want to explore but actually opening up the CSA on the floor of bends and not trying to keep it consistent (so slightly d shaped profile). Higher speed air doesn't turn was well. In bends that results in separation at at the inner radius, the turbulent low pressure zone under the separation gets bigger, and the flow zone gets smaller (restrictive). Airspeed in a bend isn't homogenous, velocity is much higher on the inner radius than the center or on the roof. I think if we add some cross sectional area around the inner radius we can help slow the air in that spot and make bends a little less restrictive.

Chrisyphus was going to test some of this in ansys when he has a chance but I need to model a handful of variations to look at.



Also this video is awesome but about a minute in he does a very good job talking so it how air doesn't want to turn:

https://youtu.be/zgUHxirCos0?si=OU5rBVvZOvEYQtQJ

[Bry5on]

There's plenty of room to do the 'hand grip' header in there. This is a 37mm extrusion with space all over the place, US headers shown for clearance reference:

[Bry5on]

This is one of the things I really want to explore but actually opening up the CSA on the floor of bends and not trying to keep it consistent (so slightly d shaped profile). Higher speed air doesn't turn was well. In bends that results in separation at at the inner radius, the turbulent low pressure zone under the separation gets bigger, and the flow zone gets smaller (restrictive). Airspeed in a bend isn't homogenous, velocity is much higher on the inner radius than the center or on the roof. I think if we add some cross sectional area around the inner radius we can help slow the air in that spot and make bends a little less restrictive.

Chrisyphus was going to test some of this in ansys when he has a chance but I need to model a handful of variations to look at.



Also this video is awesome but about a minute in he does a very good job talking so it how air doesn't want to turn:
https://youtu.be/zgUHxirCos0?si=OU5rBVvZOvEYQtQJ

I think you’re over-thinking this. That video is specific to reversion, which practically only really applies right at the transition from head to exhaust runner. Yes the flow path will follow a non-center-line path but it is super not intuitive with pulsed (and even higher speed laminar) flows as I recall. Long time since I did all my compressible fluids courses but not so long since I’ve had to deal with hot gas flows.

For the sake of argument, it’s easiest to say that acoustically it will follow the mid-line path. The air density will not be super different from inside radius to outside radius. Remember that the waves we’re scavenging move at the speed of sound and not the speed of the flow.

[3staxontheradio]

Here's two different layouts, both at their minimum primary lengths where I could still get something close to equal lengths and also get the merges placed in line with each other. The primaries can be made longer easily but not shorter without getting more extreme on bends or losing the merges being placed in line. Version on the left is inspired by the P54 headertube layout and the one on the right by the Kromer Kraft headers. Neither is a copy of anything, just following a similar routing.


I think the design on the left is a lot better, fewer bends, should fit easier, and there are more possible primary lengths so its a more flexible layout.

[Bry5on]

Beautiful. What’re you using for CAD that allows you to show the primary lengths like that?

[Cronenberged]

Here's two different layouts, both at their minimum primary lengths where I could still get something close to equal lengths and also get the merges placed in line with each other. The primaries can be made longer easily but not shorter without getting more extreme on bends or losing the merges being placed in line. Version on the left is inspired by the P54 headertube layout and the one on the right by the Kromer Kraft headers. Neither is a copy of anything, just following a similar routing.


I think the design on the left is a lot better, fewer bends, should fit easier, and there are more possible primary lengths so it’s a more flexible layout.

The Motorsport headers are true equal length there design allowed for a lot of high RPM torque but weren’t great in the low RPMs. The Epic headers were similarly designed and from all the designs I’ve seen a it’s been the best.

[3staxontheradio]

It's just polygons in 3ds Max. It's the fastest way for me to sketch stuff and when I go to make a cad model I'll bring that into SolidWorks as a reference.

[George Hill]

How close in length are you targeting?

I assume the Kromer style will be easier to tighten up the length variation?

While the P54 style will be way easier to manufacture and install/work on.

How much do you think the packaging will change when fitted to an E46 chassis? Or maybe I should say, how much will the E46 chassis and engine support arm restrict freedom of tubing layout compared to the E36?

[Bry5on]

It's just polygons and 3ds Max. It's the fastest way for me to sketch stuff and when I go to make a cad model I'll bring that into SolidWorks as a reference.

I’m using Fusion and what I’ve been doing is just pulling the volume of each runner’s body to approximate length. Getting an auto-calculated spline length in fusion would be much better though. You have a CAD program in mind? I pay for Fusion so I think I can invite folks to collaborate in a design.

[3staxontheradio]

The Motorsport headers are true equal length there design allowed for a lot of high RPM torque but weren’t great in the low RPMs. The Epic headers were similarly designed and from all the designs I’ve seen a it’s been the best.

This isn't a copy at all, everything from primary lengths, diameters, and merge design is going to end up clean sheet design but I like this basic routing path.

I think I have enough to do candidate for metal printing v1 in PLA or abs, make sure it can physically be installed with the engine in the car, and ideally do some flow tests on a flow bench with a few different anti reversion features. I THINK if an anti reversion design doesn't significantly impact flow bench numbers it's at least not going to cause problems. I also think you can probably see some difference in steady state flow if you swap directions of the part and that should also give some indication of if it's working well. Obviously steady state isn't the same as eating up short positive pressure waves but i would imagine it can indicate a trend.

[Cronenberged]

This isn't a copy at all, everything from primary lengths, diameters, and merge design is going to end up clean sheet design but I like this basic routing path.

I think I have enough to do candidate for metal printing v1 in PLA or abs, make sure it can physically be installed with the engine in the car, and ideally do some flow tests on a flow bench with a few different anti reversion features. I THINK if an anti reversion design doesn't significantly impact flow bench numbers it's at least not going to cause problems. I also think you can probably see some difference in steady state flow if you swap directions of the part and that should also give some indication of if it's working well. Obviously steady state isn't the same as eating up short positive pressure waves but i would imagine it can indicate a trend.

Not calling it a copy at all, just referencing the front bank tucking behind the back allowed them to be equal length, in essence that design features has been best. I’m excited to see what you put together I have plans in the future for a 3.5 build so might be asking for help in the future if you’ll lend it.

[3staxontheradio]

How close in length are you targeting?

I assume the Kromer style will be easier to tighten up the length variation?

While the P54 style will be way easier to manufacture and install/work on.

How much do you think the packaging will change when fitted to an E46 chassis? Or maybe I should say, how much will the E46 chassis and engine support arm restrict freedom of tubing layout compared to the E36?

This is already heavily cleaned up from the kromer kraft original design. This picture is the scan vs this tube layout- You could absolutely sit down and fiddle with the lengths more but this is pretty close before adding super convoluted tight radius bends to add length. You can see its pretty different and also I moved primaries 1 and 2 to sneak them under the engine mount instead of wrapping around it so that it would be possible to make this header as two solid banks instead of individual primaries that slip fit into the merge.



I'm not 100% sure on E46 fit yet. I need to look at that closely next. I have an e46 chassis here I can scan but no way to correctly get the S54 placed into the right spot (its a 330i with an m54) Bry5on shared a scan with me a while ago that I think includes some E46 chassis in it. I might be able to align that with my E46 scan and get the engine placed correctly. Also I was under an E46 looking at space last week and I think there is actually less room on the E46 than the E36 which I was surprised by because the E46 chassis is wider. If it's just the engine support arm causing an issue then the designed based on the p54 has plenty of room to move primary number 4 away from the arm. Not so much on the other design without really throwing off the lengths.



As far as how close to equal goes. This is mm of delta from the average for each of the two designs. P54 style is the red line and kromer kraftish layout is the blue line. Right now its at about a 50mm spread which I think is pretty good:

[3staxontheradio]

Not calling it a copy at all, just referencing the front bank tucking behind the back allowed them to be equal length, in essence that design features has been best. I’m excited to see what you put together I have plans in the future for a 3.5 build so might be asking for help in the future if you’ll lend it.

Yeah I just meant that whatever characteristics that layout has show probably wouldn't be reflected in this since the basic dimensions will be very different.

[Bry5on]

I’m targeting +/-<3 mm, so +/-25 seems pretty bad! What mean length are you going for, and have you settled on a half-way step or something like a 2/3, etc? I was looking at the T50 and it appears the step is super late, more than 2/3 in.

[ApexPothole]

Also this video is awesome but about a minute in he does a very good job talking so it how air doesn't want to turn:

Thanks for the video rec. Made for some good listening at work.

I have an e46 chassis here I can scan but no way to correctly get the S54 placed into the right spot (its a 330i with an m54)

I believe the part numbers for the front right motor mount arms and the crossmembers are both identical between the S54 and M54 cars. I would think that you could use the motor mount as a common point between the models. Alternatively, IDK if you can get any through holes on the bellhousing bosses but that could give you an locating point, I would think?