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  #41  
Old 05-21-2013, 11:23 AM
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Originally Posted by TheBandit View Post
Are you talking about the last two that I posted? The thing I don't like about either of them is they really look like an H-pipe that's been added onto to create a volume. The transition is not abrupt from collector to terminator box. If the goal is to reflect the pressure pulse at the transition and attenuate harmonics within the box, it seems the transition should ideally replicate an open ended pipe. On these some portion of the pipe entering the box continues on out of the box, so I don't see a strong reflection point from the collector and I suspect the flow would remain attached to the wall. I'm not sure if that's a bad thing or not. Perhaps it would weaken the reflection, but spread it out over a very slightly wider RPM band.

I really have no idea what I'm talking about (as usual)
Yes in particular but frankly all of them...

Yes the point is to reflect the wave and that is something that the "X" fails to do. The X can only work if it times the pulses at the X making all dimensions and locations critical. The H by contrast is much more forgiving in all aspects.
Flow is located in the center of the pipe due to boundary layer effects.
If not using a correct volume box the walls ideally would be as small and as smooth as possible while keeping the flow rate below about 300FPM and the pressure at 0PSIG to negative and (excluding a TB) there would be no changes in diameter/shape that will increase the boundary layer OR fail to direct the flow such as the last box...
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  #42  
Old 05-21-2013, 11:28 AM
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JaysinSpaceman JaysinSpaceman is offline
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Without seeing the insides of these boxes none of us know what we're talking about. I really don't see how that last one is going to work without making totally turbulent flow which is just going to be stumbling over itself to get out of that box. I really think that you need to look at the fluid dynamics as well as the pressure pulses and all that is WAY over my head. When I build mufflers and exhaust systems I go by the rules that I see in observable nature, square corners make turbulence and eddies, these things cause restrictions to flow and if your whole goal is flow then turbulence needs to be minimized so I wouldn't use square corners. My point is that while you are looking for the volume change it needs to be done in a controlled manner and there would need to be internal baffling to guide the exhaust gases through that box in a laminar flow or you end up with a traffic jam at the exit.

But I am pulling all that out of my backside because I don't have a clue about fluid dynamics besides what I observe.

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  #43  
Old 05-21-2013, 12:00 PM
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I think what Vizards article is trying to point out is that simple flow restriction is not the critical design factor in the exhaust system, but rather the harmonic tuning. The primary restriction in the system is the actual exhaust valve/port, which is why it's important to apply as little pressure (preferably vacuum) on the backside of the valve as possible when the valve is open. This is accomplished with harmonic tuning of the primary and secondary exhaust tubes. If you can get that pressure wave to go negative when the valve is open, you can not only draw exhaust out of the cylinder, but also draw fresh air from the intake side during the overlap period, improving volumetric efficiency. This is only going to happen over a short window for fixed exhaust dimensions. The terminator box helps you tune the secondary (collector) harmonics while attenuating any harmonic effects downstream.
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  #44  
Old 05-21-2013, 02:10 PM
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Quote:
Originally Posted by TheBandit View Post
I think what Vizards article is trying to point out is that simple flow restriction is not the critical design factor in the exhaust system, but rather the harmonic tuning. The primary restriction in the system is the actual exhaust valve/port, which is why it's important to apply as little pressure (preferably vacuum) on the backside of the valve as possible when the valve is open. This is accomplished with harmonic tuning of the primary and secondary exhaust tubes. If you can get that pressure wave to go negative when the valve is open, you can not only draw exhaust out of the cylinder, but also draw fresh air from the intake side during the overlap period, improving volumetric efficiency. This is only going to happen over a short window for fixed exhaust dimensions. The terminator box helps you tune the secondary (collector) harmonics while attenuating any harmonic effects downstream.
"Harmonic Tuning" is also known as "Organ Pipe Tuning" and was replaced with "Finite Amplitude Wave" tuning more then a decade ago.
I understand that you may be referring to tuning the FAW to its "harmonic" frequency I simply want to make sure that the difference is at-least in the conversation as the results will be different in every aspect.
I should note that without a serious development program at best the result will be measurable only in about a 500-RPM range and generally will simply rock the curve around peak torque.
So again I can say on the street get as free flowing as you can with the sound you want
Yes, I am an exhaust nerd, no I do not fully understand it (lack of advanced mathematical skills) BUT I am dangerous
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  #45  
Old 03-04-2014, 07:21 PM
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Digging this thread up from dead, I have matured my Nova's exhaust system to this state:



I dare not take closer photos or my (lack of) fabrication skills would be apparent, however the basic specs are 3" aluminized steel pieced together with mandrel bends into Dynomax VT mufflers (straight through design with a gimmick-valve to quiet them at part throttle). Per Dynomax published data, even with the valve, these flow 840cfm each @ 20" H2O so they should not be restricting power (the 2.2cfm/hp rule would suggest 760hp "loss free").

I have decided a proper terminator box is outside of what I have time, space or skill to build and would like to do an H-pipe, however now I have no idea where to find out what size and where to locate such a device.

E or anyone else have suggestions on where to put the H-pipe and what dia it should be? Do I put it approximately where I would want the collector to "terminate"?

I am a bit concerned any H pipe I put in is going to be too far from the collector because of constraints around the transmission.
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  #46  
Old 03-04-2014, 07:32 PM
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I remeber a method described awhile back where you paint a line from the collecter back and where the paint changed to burnt/discolored that is where you would put the "H".
I suppose using a temp "paint" stick and would be far more scientific. I have no idea what temp stick you would want use, or if this method is even worth a damn.
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  #47  
Old 03-04-2014, 08:42 PM
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The above mentioned Paint trick works.
However, you also make the point of put it where it fits!
Use noting smaller then 2.5" for the "H".

Tail pipes?, if not aim the exhaust at the ground under the differential (center).

E
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  #48  
Old 03-05-2014, 05:02 PM
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Your suggestions would indicate I should position the H pipe at the same location I would want a collector to end if I were doing an open exhaust or terminator box. Yes?

Quote:
Originally Posted by entropy View Post
Tail pipes?, if not aim the exhaust at the ground under the differential (center).
Turn downs for now. I want tailpipes to keep the fumes away, but need to work out changes to the rear suspension first. Also given the time and frustration of fitting just the basic components of the exhaust, I will probably look to have the tailpipes made by a professional. I have to recognize my own limitations and they are many (time, skill, frustration, etc)
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  #49  
Old 03-05-2014, 06:24 PM
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Originally Posted by TheBandit View Post
Your suggestions would indicate I should position the H pipe at the same location I would want a collector to end if I were doing an open exhaust or terminator box. Yes?
The paint stripe is a single layer quick stripe and you fire the engine for under a minute; one of two things will happen the paint will burn to a point and stop or the paint will burn to a point stop and then several inches back from that point it will burn a spot. In the first case you would put the crossover or H-pipe at the end of the burn or right on the spot burn.
You are looking for the point where most of the energy has done its work and you are tapping the FAW. Granted paint stripes are crude as all get out, we use what we have and F1 uses magic


Quote:
Originally Posted by TheBandit View Post
Turn downs for now. I want tailpipes to keep the fumes away, but need to work out changes to the rear suspension first. Also given the time and frustration of fitting just the basic components of the exhaust, I will probably look to have the tailpipes made by a professional. I have to recognize my own limitations and they are many (time, skill, frustration, etc)
You ether like this stuff or you don't I've not found that many in the middle.

E
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  #50  
Old 03-05-2014, 11:16 PM
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Oh I like the stuff, don't get me wrong, I love it. There are just some things I only need to do once and beyond that I am mostly interested in designing new things.
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  #51  
Old 03-05-2014, 11:27 PM
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Originally Posted by entropy View Post
Granted paint stripes are crude as all get out, we use what we have and F1 uses magic
I'm not all that convinced this method holds water. I'll think through it but I can't think of a scientific reason you'd have a sudden drop in temperature or heat transfer anywhere near a specific wavelength.

Take a look at this thread and a relevant quote:
http://www.speedtalk.com/forum/viewtopic.php?p=43333

Quote:
i posted Pics of this a few years ago on a Forum.
just used Krylon Chevy Orange paint on one pair of Headers
to paint a long stripe down the Collector length,
made a Dyno Pull...went and cut at the spot where paint changed colors,
painted another stripe....re-Dyno test again...lost Torque + HP
again cut at the new spot paint changed color....
re-Dyno test again...lost more Torque + HP

everytime you cut to that spot..if you again paint another Stripe,
make another Dyno test...the spot moves..
the spot continously moves no matter how many times you Dyno...
it will "continually" move towards the Head..you won't have a Header left
and no Torque !

i went thru this with 2 different SuperStock Racers on
2 different engines....these were brand new Headers,
uncoated unpainted...so it was very easy to see
where the color point was....we cut it exactly at that point
and lost Torque :)
i painted a stripe for next Test,
we made another Pull....then cut the Collector at that point,
made another Test ..lost Torque again ! :)
i asked that Guy..you want to keep trying that ??
he said no..i'm finished with that Theory :)

then i had to Tig back that Collector to the Length it was originally,
..after a few more Tests..i added more Length and HP + TQ increased,
still the "mark" showed the wrong spot to cut the Collector.

if that Theory has ever worked ??? ..its been because it was pure chance !
to any Racer that has by pure chance seen that Theory work,
..i say go back and paint another stripe...make another run,
and you'll see the "mark" keeps moving...now cut it at that new "mark"...
keep playing with that...and let me know if your RaceCar goes faster ??
good luck !
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  #52  
Old 03-05-2014, 11:59 PM
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I've never used the paint stripe that way...
But one thing stands out; every time you change anything in the exhaust it will change the paint stripe burn.
That is why you put the complete (as close as possible) system on to test.
Testing on the Dyno is truly the way to get into the ball park BUT you have to test the full exhaust and the exact components. You can take a set of Dyno headers and swap em for the set that actually fits in the chassis, dimensionally the same in every way, except the bend locations and see significant power changes generally losses.

E
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  #53  
Old 03-17-2014, 03:14 PM
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Here is anther interesting crossover design implemented on the Honda CX500 (and probably similar motorcycles). This is the first factory/oem terminator box I've come across.





Not really sure what to say about this one other than it's very interesting. From my minimal reading on the subject, this particular crossover / terminator box has a very strong effect on how well the engine performs as well as how the carbs are jetted. Apparently the different pipe lengths internal to the box are to compensate for uneven lengths leading from the engine into the box. The result is that the pipe length from the head until it ultimately terminates inside the box is equal on each cylinder.
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  #54  
Old 04-04-2014, 01:31 PM
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For what it's worth...more discussion about terminator boxes:

http://speedtalk.com/forum/viewtopic...d6c4708753e4fa
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