Heymow - Lawnmower Racing Forum

General => Coffee Shop => Topic started by: Racer57 on December 01, 2013, 06:19:29 pm

Title: Square tube or rectangle tube exhaust
Post by: Racer57 on December 01, 2013, 06:19:29 pm
Has anyone ever tryed a square or a rectangle tube exhaust system? And if you have any good or bad things about it
Title: Re: Square tube or rectangle tube exhaust
Post by: GunSlinginJoe13 on December 01, 2013, 07:39:00 pm
Yes there is a guy who has square tube(I think or its rectangle tube).  His name on here is Flipper.
Title: Re: Square tube or rectangle tube exhaust
Post by: Jeff Digou (Pitguy) on December 01, 2013, 07:56:27 pm
Guys use Round to rectangle. Never seen all square or rectangle exhaust
Title: Re: Square tube or rectangle tube exhaust
Post by: russell jennings on December 01, 2013, 08:11:18 pm
Tom L has a square tube exhaust on his mod-xr. seems to work fine.
Title: Re: Square tube or rectangle tube exhaust
Post by: BIG AL 202 on December 01, 2013, 09:34:42 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:
Title: Re: Square tube or rectangle tube exhaust
Post by: Racer57 on December 01, 2013, 09:38:12 pm
I was thinking it would give decent back pressure, and I was hoping it would sound different
Title: Re: Square tube or rectangle tube exhaust
Post by: Burwell555 on December 01, 2013, 11:40:45 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
Title: A historical note on square exhausts
Post by: 3v0 on December 03, 2013, 04:20:43 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 :)
Title: Re: Square tube or rectangle tube exhaust
Post by: birdman_express on December 03, 2013, 07:32:01 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.
Title: Re: Square tube or rectangle tube exhaust
Post by: BIG AL 202 on December 03, 2013, 09:09:29 pm
 :twothumbsup:
Title: Re: Square tube or rectangle tube exhaust
Post by: redline on December 03, 2013, 09:59:34 pm
After a few crashes, my exhaust and steering wheel typically resemble a rhombus. It does not seem to affect performance however.
Title: Re: Square tube or rectangle tube exhaust
Post by: RFMotorsports on December 04, 2013, 04:51:34 am
After a few crashes, my exhaust and steering wheel typically resemble a rhombus. It does not seem to affect performance however.

 :lol3:

Title: Re: Square tube or rectangle tube exhaust
Post by: Flipper on December 04, 2013, 02:01:13 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.

(http://i146.photobucket.com/albums/r244/joeynahas839/2011-03-29007.jpg) (http://s146.photobucket.com/user/joeynahas839/media/2011-03-29007.jpg.html)
Title: Re: Square tube or rectangle tube exhaust
Post by: Flipper on December 04, 2013, 02:45:01 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.
Title: Re: Square tube or rectangle tube exhaust
Post by: BIG AL 202 on December 04, 2013, 02:47:01 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!
Title: Re: Square tube or rectangle tube exhaust
Post by: Flipper on December 04, 2013, 04:26:20 pm
How much time and effort do you want put in for a finely tuned exhaust.
Agreed and True!
Agreed, They did the calcs for me but they owed me a favor so we worked it out in trade. ........it's a mower for Christ's sake! LOL.....Agreed Al!
Title: Re: Square tube or rectangle tube exhaust
Post by: BIG AL 202 on December 04, 2013, 05:02:42 pm
 :twothumbsup:
Title: Re: Square tube or rectangle tube exhaust
Post by: berthyd on December 04, 2013, 07:35:44 pm
My exhaust is rhomboid. I don't know what that is, but I'm sure no one will say it flows better or worse than round.

Bert
Title: Re: Square tube or rectangle tube exhaust
Post by: Egoracing on December 04, 2013, 09:33:08 pm
There are headers in racing made from square tubing, Not in NASCAR because in the rules it specifically says round or oval tube. I come from 25+ year background in oval track racing and they tend to make a showing every so often in limited motor classes until rules are made against them. A square tube with the same maximum dimensions as a round tube will have more area inside the tube. Also Square shapes keep air flow laminar and keep turbulence down. That is why Racing series use square and rectangle holes for air to cooling systems. The sets I have seen are VERY crack prone even when well supported.  http://i41.photobucket.com/albums/e286/Pinionangle/header.jpg
Title: Re: Square tube or rectangle tube exhaust
Post by: BIG AL 202 on December 05, 2013, 08:15:34 am
There are headers in racing made from square tubing, Not in NASCAR because in the rules it specifically says round or oval tube. I come from 25+ year background in oval track racing and they tend to make a showing every so often in limited motor classes until rules are made against them. A square tube with the same maximum dimensions as a round tube will have more area inside the tube. Also Square shapes keep air flow laminar and keep turbulence down. That is why Racing series use square and rectangle holes for air to cooling systems. The sets I have seen are VERY crack prone even when well supported.  http://i41.photobucket.com/albums/e286/Pinionangle/header.jpg
THOSE DIFFENTLY LOOK, WELL, DIFFERENT! IN A STRANGE WAY! LOL
Title: Re: Square tube or rectangle tube exhaust
Post by: GRUBDIGGER on December 05, 2013, 04:20:54 pm
THOSE DIFFENTLY LOOK, WELL, DIFFERENT! IN A STRANGE WAY! LOL

YES THEY DO. IVE NEVER SEEN THAT USED BEFORE.
Title: Re: Square tube or rectangle tube exhaust
Post by: Flipper on December 05, 2013, 04:45:56 pm
YES THEY DO. IVE NEVER SEEN THAT USED BEFORE.



Grub....I am doing Mrs. Digger's Exhaust! LOL....see you Sat? 4pm?
Title: Re: Square tube or rectangle tube exhaust
Post by: BIG AL 202 on December 05, 2013, 05:56:38 pm
 :twothumbsup: LOL
Title: Re: Square tube or rectangle tube exhaust
Post by: Egoracing on December 05, 2013, 06:29:50 pm
 The flow is supposed to be better but like I said, $$$$, about 3 times the cost of regular headers due to the labor in making them. Again, VERY VERY crack prone. We have raced against them when I was crew chief on a dirt late model and I did not see anything that made me think we were lacking anything using the headers we were running.