H-pipe/termination box.

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chevyfreak
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H-pipe/termination box.

Post by chevyfreak »

I know there is a number of discussions out there regarding pressure wave termination boxes, different ideas, some worked and then some didnt work or last long. For me its a thing that needs more exploring.

I'm currently designing my exhaust setup for my 63 c10 with pontiac power, and in pondering on the h-pipe, why not a H chamber.
As in used on some motorcycles.
It can work as a balance between the 2 banks and maybe even work as a termination box.
Any thoughts on this? Or comments?

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NewbVetteGuy
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Re: H-pipe/termination box.

Post by NewbVetteGuy »

I'm most curious what happens to the effectiveness of a wave termination box as the volume drops further and further from the 2x engine displacement guideline that I've heard before.

Any rough guess what the volume of that "H-pipe termination box" would be as compared to your engine displacement?


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Re: H-pipe/termination box.

Post by chevyfreak »

NewbVetteGuy wrote: Tue Jan 25, 2022 3:59 pm I'm most curious what happens to the effectiveness of a wave termination box as the volume drops further and further from the 2x engine displacement guideline that I've heard before.

Any rough guess what the volume of that "H-pipe termination box" would be as compared to your engine displacement?


Adam
For me as well. Running a single box and going 2x455ci size its going to be huge. I'm checking on space available and i have space but not like its going to make it easier.
If i go round i quess about a 4 to 4.5 inch dia, and see on how long i can make it , but with a flat type it works out better space wise, biggest issue is keeping a flat type box together (i read everywhere they crack and/or blow up) and then they drone as well.
Construction wise i was thinking maybe build it like those boom tubes from nascar.

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Re: H-pipe/termination box.

Post by barnym17 »

I have a honda 1979 cx 500 v twin that uses a box like that each cylinder dumps into that then the exhaust pipes exit to the mufflers.So it is evidently an idea thats been around awhile.
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Re: H-pipe/termination box.

Post by MetricMuscle »

I've been exploring how best to go about building something similar and from what I've gathered, a large cross section change at the end of the collector is very important. You can include some of the volume of the piping that exits the Terminator Box which really helps to achieve the 2X volume.

The shape needs to be either non flat, non parallel sides and/or braced more closely together. Just look at catalytic converters that are flat on the top and bottom but the sheet metal has beads embossed to create rigidity. Wall thickness helps but can't overcome the need for bracing.
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Re: H-pipe/termination box.

Post by chevyfreak »

barnym17 wrote: Wed Jan 26, 2022 5:37 am I have a honda 1979 cx 500 v twin that uses a box like that each cylinder dumps into that then the exhaust pipes exit to the mufflers.So it is evidently an idea thats been around awhile.
Discovering pics from the bikes is what got me thinking.
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Re: H-pipe/termination box.

Post by chevyfreak »

MetricMuscle wrote: Wed Jan 26, 2022 7:45 am
The shape needs to be either non flat, non parallel sides and/or braced more closely together. Just look at catalytic converters that are flat on the top and bottom but the sheet metal has beads embossed to create rigidity. Wall thickness helps but can't overcome the need for bracing.
I'm thinking to do like the nascar boom tube design.
Gives some volume and there is bracing build into it depending on how its done.

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Re: H-pipe/termination box.

Post by NewbVetteGuy »

I used to really like the idea of a termination box: Try to make a full-length and quiet(er) exhaust system perform and "tune" like it is an open-header system.

Now I feel like my "mental pendulum" is swinging and I am kinda feeling like the Calvin Elston approach of just maximizing velocity everywhere and letting all the 2:1 merges just attenuate the waves at each merge point makes more sense. (Then add high flow mufflers where / when required to reduce sound levels.)

If an H-pipe and an X-pipe reduce sound levels; wouldn't a 2:1 exhaust merge do the same? I can't see how it wouldn't.

All the complexity and weight a custom fabrication for the term box and still dealing with trying to take advantage of wave tuning that only helps in a particular RPM range vs. an approach that maximizes velocity everywhere...

If there were off-the-shelf really good tri-y designs or termination boxes for my car, I'd probably be more single-minded about it, but as that's not the case, the pendulum swings continue...


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Re: H-pipe/termination box.

Post by digger »

In my opinion the aspect ratio matters, it should not be too wide and too short as you need to slow the gas down other wise it doesn't see the full area change. So i think it should be long and relatively narrow such as a gutted oval muffler with curved surface so maybe a 2 or 3 to 1 aspect ratio (e.g. 10" wide 20 / 30" long or whatever gives the volume)
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Re: H-pipe/termination box.

Post by chevyfreak »

digger wrote: Wed Jan 26, 2022 6:39 pm In my opinion the aspect ratio matters, it should not be too wide and too short as you need to slow the gas down other wise it doesn't see the full area change. So i think it should be long and relatively narrow such as a gutted oval muffler with curved surface so maybe a 2 or 3 to 1 aspect ratio (e.g. 10" wide 20 / 30" long or whatever gives the volume)
One of my ideas as well.
My mind has been all over on this.
So many ways possible that i cant settle my mind,

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Re: H-pipe/termination box.

Post by skinny z »

NewbVetteGuy wrote: Wed Jan 26, 2022 2:59 pm to take advantage of wave tuning that only helps in a particular RPM range vs. an approach that maximizes velocity everywhere...
I was under the impression that a termination with the correct collector length in front of it (say a length designed for increased torque as opposed to increased HP) will produce a boost in output everywhere in the rev range.
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Re: H-pipe/termination box.

Post by digger »

NewbVetteGuy wrote: Wed Jan 26, 2022 2:59 pm I used to really like the idea of a termination box: Try to make a full-length and quiet(er) exhaust system perform and "tune" like it is an open-header system.

Now I feel like my "mental pendulum" is swinging and I am kinda feeling like the Calvin Elston approach of just maximizing velocity everywhere and letting all the 2:1 merges just attenuate the waves at each merge point makes more sense. (Then add high flow mufflers where / when required to reduce sound levels.)

If an H-pipe and an X-pipe reduce sound levels; wouldn't a 2:1 exhaust merge do the same? I can't see how it wouldn't.

All the complexity and weight a custom fabrication for the term box and still dealing with trying to take advantage of wave tuning that only helps in a particular RPM range vs. an approach that maximizes velocity everywhere...

If there were off-the-shelf really good tri-y designs or termination boxes for my car, I'd probably be more single-minded about it, but as that's not the case, the pendulum swings continue...

Adam
the two (2) aren't mutually exclusive though. Calvin exhaust still use tuned lengths otherwise the length would always be the shortest possible. He is also not maximising velocity but tuning for a higher velocity (compared to conventional exhausts) close to the head and lowering gradually. This only does so much so still needs to be combined with the right lengths.

If you had two mufflers on a x/y pipe and a single muffler with the y-pipe, then the y-pipe will likely be noisier
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Re: H-pipe/termination box.

Post by NewbVetteGuy »

skinny z wrote: Wed Jan 26, 2022 9:32 pm
NewbVetteGuy wrote: Wed Jan 26, 2022 2:59 pm to take advantage of wave tuning that only helps in a particular RPM range vs. an approach that maximizes velocity everywhere...
I was under the impression that a termination with the correct collector length in front of it (say a length designed for increased torque as opposed to increased HP) will produce a boost in output everywhere in the rev range.
My impression is the opposite and that a termination box makes a full-length exhaust perform as close as possible to an open header exhaust when the end of the secondary pipe and the opening into the wave term box are in the same location.

If the exhaust pressure waves HELP when they arrive at the right time, don't they have to hurt when they arrive at the wrong time?
-I'd swear I remember a Vizard diagram that showed the relatively narrow band in which intake runner wave tuning is beneficial and compared that to the must wide RPM band in which exhaust wave tuning is beneficial, but after looking for a bit I couldn't find it.
-I immediately think of all the intake runner length dynos showing the torque peaks and dips pushing the curve left or right; surely exhaust wave tuning is doing the same even if it is a "wider" wave in terms of width of the RPM band that it takes effect, right?

My understanding with the tri-y, maximize velocity approach is that all those 2:1 merges, a modern 4:1 merge collector, and/or megaphones, is that they all attenuate the pressure waves so they flow more from the valve outward and far less when they reflect back inward towards the valve. -To me that sounds like a design that can better be optimized to work in a broader RPM band vs. just a traditional tuned 4:1 without those "wave attenuation features"?

(Does that mean that the cylinder would see depressions with lows that are not as low at the torque peak / torque that isn't as high vs. a more traditional tuned 4:1 system, but also has higher lows via less reversion?) -That's probably my 1/2-baked guess.
IF the exhaust wave tuning only works by having the pressure wave travel to the end of the pipe, back to the valve, and then as it's leaving again the depression behind the wave does it's magic, AND you have features in the exhaust that prevent that wave from traveling backwards, then you have to be losing some of the benefit in the tuned RPM range but not having as much negative impact outside of the tuned range. -The increased average velocity of keeping everything flowing fast helps you everywhere, so the net is an average gain vs. the "strongly tuned" traditional design if looking at a wide RPM range.

[Edit] Trying to simplify my thoughts: My current thinking is that the older tuned designs see "stronger wave action" (higher highs; lower lows) reflecting back to the exhaust valve; and that the high velocity designs and some specific exhaust features (merge collectors, megaphones, ??) probably result in "reduced wave action/amplitude" at the exhaust valve but the reduced reversion and higher average exhaust velocity makes it better in broad RPM applications.

Just random musings and my thoughts on how I THINK it works, so one of the giant brains on here can hopefully correct where I've gone wrong.



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Re: H-pipe/termination box.

Post by digger »

PWTB is supposed to act as the end of the exhaust system to preserve the collector lengths of the open header (however optimum or sub optimal these may be). This allows you to put sensible sized muffler(s) and only need to worry about back pressure (pressure losses) and not screwing the tuned lengths that you get from a conventional full exhaust system. The aim is not to gain, it is to not to lose.
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Re: H-pipe/termination box.

Post by MetricMuscle »

digger wrote: Thu Jan 27, 2022 8:44 pm PWTB is supposed to act as the end of the exhaust system to preserve the collector lengths of the open header (however optimum or sub optimal these may be). This allows you to put sensible sized muffler(s) and only need to worry about back pressure (pressure losses) and not screwing the tuned lengths that you get from a conventional full exhaust system. The aim is not to gain, it is to not lose.
This is how I understand it too. A large change in cross section area, like a 4-1 merge, creates the strongest wave which can help boost power at the rpm it is tuned for but also have the same negative effect below. If'n I understand correctly, a tuned length for 6,000rpm also helps 3,000rpm and 1,500rpm but hurts 4,500rpm and 2,250rpm. A 4-2-1 or Tri-Y sacrifices the gains of large cross section area change but doesn't suffer the nulls in between. Any exhaust system is going to have a wave to get rid of, just depends on how you wanna use it.

So is it important for there to be a large area change at the end of the collector for a PWTB to work? Would a tapered/megaphone collector instead of straight single diameter work using a PWTB? Could the area change between the end of the collector and Box be less if using a tapered/megaphone collector?

I think I read somewhere that David Vizard suggested that using a crossover tube in conjunction with a PWTB works better. He recommends the crossover tube be at the beginning of the collector.
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