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Author Topic: Square tube or rectangle tube exhaust  (Read 2375 times)
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Racer57
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« on: December 01, 2013, 05:19:29 PM »

Has anyone ever tryed a square or a rectangle tube exhaust system? And if you have any good or bad things about it
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« Reply #1 on: December 01, 2013, 06:39:00 PM »

Yes there is a guy who has square tube(I think or its rectangle tube).  His name on here is Flipper.
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« Reply #2 on: December 01, 2013, 06:56:27 PM »

Guys use Round to rectangle. Never seen all square or rectangle exhaust
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« Reply #2 on: December 01, 2013, 06:56:27 PM »

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« Reply #3 on: December 01, 2013, 07:11:18 PM »

Tom L has a square tube exhaust on his mod-xr. seems to work fine.
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« Reply #4 on: December 01, 2013, 08:34:42 PM »

ROUND FLOWS BETTER! NOT TO SOUND BAD BUT IF SQUARE TUBING WAS BETTER THE WHOLE WORLD WOULD BE USING IT! I DO BELIEVE THE FLOW DOES NOT LIKE THE CORNERS!  lol
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« Reply #5 on: December 01, 2013, 08:38:12 PM »

I was thinking it would give decent back pressure, and I was hoping it would sound different
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« Reply #6 on: December 01, 2013, 10:40:45 PM »

Back pressure can be tuned by many things. Pipe size, primary lengths, collector design etc. Air flow likes round ports. Hence why all the wicked cylinder heads on the market are "oval port" style versus the "rectangle ports" commonly found on a lot of the older muscle car engines etc
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« Reply #7 on: December 03, 2013, 03:20:43 AM »

A quick net search did not turn up anything to support this but I recall reading in the early days of auto racing a farmer/racer noticed his square elevators would move more grain then round ones.   

He tried fitting square exhausts to his race car but was unhappy with the results and went back to round pipes.

100 years and the same question pops up here smile
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« Reply #8 on: December 03, 2013, 06:32:01 AM »

If square was the way to go, Nascar would be using it.
For ground clearance, they do use what they call ovate,
which is just flattening out the round to oval.  Nothing really to gain
from it from what I understand in HP standpoint, just clears the
ground better. It does make a different sound. If you have a
dyno, do both, and see what it does.
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« Reply #9 on: December 03, 2013, 08:09:29 PM »

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« Reply #10 on: December 03, 2013, 08:59:34 PM »

After a few crashes, my exhaust and steering wheel typically resemble a rhombus. It does not seem to affect performance however.
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« Reply #11 on: December 04, 2013, 03:51:34 AM »

After a few crashes, my exhaust and steering wheel typically resemble a rhombus. It does not seem to affect performance however.

 lol3

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Luke Rakoske
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« Reply #12 on: December 04, 2013, 01:01:13 PM »

Yes there is a guy who has square tube(I think or its rectangle tube).  His name on here is Flipper.

For the most part, it is self preference per application.

It is round to a straight rectangular long "Chute" with a 80deg turn. This changes the sound drastically. However, to maintain some sort back pressure, My CFM/Flow/Temps/RPM Calcs were done by a local shop called "Speed Unlimited-House of Balance" by some fellow mechanical engineers.   I was amazed as to how much mathematics and variables were involved.(They hand make custom exhaust for all kinds of race cars and more) There are small 1/4" baffles welded in the 2x3 Square "chute" portion of my exhaust to make the exhaust more turbulent and slow it down, thus gaining lost back pressure. They nailed it.  A good portion of Mason Dixon racers now have my similar exhaust.

Oval will provide similar performance.

Yes, in some cases, round pipe does have better flow characteristics within a smaller volume pipe. However, rectangular pipe, if made correctly, will have very similar performance(if not better), and will typically have larger volume, enabling it to handle higher CFM flows. Take a 2" Circle and a 2" Square, The square has more volume. In theory, a smaller exhaust could be used
if it were rectangular with little bends or resistance. However, I just use the termination section of the exhaust system in rectangular medium.(304 2x3x.120 Stainless Steel)

This is actuality if more self preference- flat or round. At work I also design & Engineer ductwork for HVAC Air flow systems.
Some days I use rectangular, some days I use round spiral...this depends on where it needs to be. Exposed I use round spiral duct, for applications where it needs to be hidden in a drop ceiling, I use flat.

One reason I started using use rectangular exhaust(tail piece) 9 years ago, is no one else does or did, and gets it right. Why be a clone?.

The higher register of frequency has a shorter, weaker wavelength, when it hits a flat surface it weakens significantly.
It does not deteriorate as much in round pipe.
The lower register of frequency has a stronger, longer wavelength, thus making it thru the pipe with little deterioration.
This will give the lower register "Note" (Sound) of something aggressive & more desirable,  not so much a noisy rattle trap.

The old philosophy of cutting the pipe at 18" or where the paint burns off is exactly that...a far fetched philosophy that someone made up for one particular application and engine, not for all.


FYI.....key in "Nascar Exhaust" under google images........As mentioned above by Birdman, NASCAR uses rectangular chutes more often than not, and there is a reason for that. Space restraints due to low ground clearances, They need to maintain the flow volume so the obvious choice was a rectangular chute. At the time, the unknown benefit was a surprisingly different tone or note. Not really proven if any gain in performance.

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« Reply #13 on: December 04, 2013, 01:45:01 PM »

Tom L has a square tube exhaust on his mod-xr. seems to work fine.

I think Tom did that to mess with my limited cranial capacity(Head), however, it works, and works well.
It is rather short, but if he's happy and winning, who cares.
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« Reply #14 on: December 04, 2013, 01:47:01 PM »

This sounds simular to what I have found with megaphone and reverse megaphone style exhaust. you really need dyno time to sort out what really works and what does not! Then the other problem is at what rpm does the exhaust work. How much time and effort do you want put in for a finely tuned exhaust.
I think Tom did that to mess with my limited cranial capacity(Head), however, it works, and works well.
It is rather short, but if he's happy and winning, who cares.
Agreed and True!
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