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Oval Exhaust System - Hardtuned.net

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Oval Exhaust System 

91 replies to this topic

#1 JoELMaN

  • Joined:25-October 05
  • Location:Australia NSW

Posted 07 May 2013 - 08:35 PM

I'm looking at making an oval exhaust to try and gain a bit more clearance. Has anyone here done this?

Does anyone know where I can get hold of some oval tubing and oval to round transitions in Australia? Otherwise I am thinking I will just split a 2" pipe and weld a 50mm flat between them.

Below is a couple of pics of a 'powered by max' system on an s13.

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Edited by JoELMaN, 07 May 2013 - 08:35 PM.


#2 sr20pulsar

  • Joined:20-September 08
  • Location:Australia NSW
  • Car:NXR Turbo Coupe

Posted 07 May 2013 - 09:45 PM

Cross sectional area compared to tube would be interesting.

#3 26_S13

  • Joined:29-September 11
  • Location:Australia QLD
  • Car:s13

Posted 07 May 2013 - 10:11 PM

Id be more worried about not being able to run a cat becuase of the shape of the tube then abit of ground clearance...

#4 fiend.

  • Joined:24-April 05
  • Location:Australia VIC

Posted 07 May 2013 - 10:40 PM

If you're going for ground clearance for legality, then it would seem to me a hard system to put mid mufflers and resonators on, let alone a cat.

#5 Drunken Monk

  • Joined:21-May 09
  • Location:Australia VIC
  • Car:180sx

Posted 07 May 2013 - 11:05 PM

So many welds, so many more places to rot out and crack the way you said about splitting 2" and welding in sheet metal.

#6 atari4x4

  • Joined:17-December 10
  • Location:Australia SA

Posted 07 May 2013 - 11:20 PM

$55 for 6m http://www.gumtree.c...long/1003919040
Posted Image

#7 STR8E180

  • Joined:30-April 03
  • Location:Australia NSW
  • Car:GTR R34 V-SPEC

Posted 08 May 2013 - 05:08 AM

U can tuck up a 3 inch exhaust fairly high of your making your own exhaust
I'm able to make it the same level as the chassis rail

#8 JoELMaN

  • Joined:25-October 05
  • Location:Australia NSW

Posted 08 May 2013 - 07:19 AM

 fiend., on 07 May 2013 - 10:40 PM, said:

If you're going for ground clearance for legality, then it would seem to me a hard system to put mid mufflers and resonators on, let alone a cat.

Mid mufflers would certainly be hard to tuck up above the rails, maybe a big muffler right at the back after the subframe. At the moment my metal cat sits up nearly level with the rails.

 fyjosh, on 07 May 2013 - 11:05 PM, said:

So many welds, so many more places to rot out and crack the way you said about splitting 2" and welding in sheet metal.

Yeah doing it that way is far from ideal. Which is why I ask if anyone has bought any in Aus before.

 STR8E180, on 08 May 2013 - 05:08 AM, said:

U can tuck up a 3 inch exhaust fairly high of your making your own exhaust
I'm able to make it the same level as the chassis rail

How about around the subframe and diff area?

#9 STR8E180

  • Joined:30-April 03
  • Location:Australia NSW
  • Car:GTR R34 V-SPEC

Posted 08 May 2013 - 09:08 AM

I can still get it around the diff area very high
In fact it's easier to tuck up around the diff area
I done one a while back on a mates car
It was 3.5 inch and it was tucked up higher then any 3 inch exhaust system off the shelf which u buy in a kit

#10 Stilvia

  • Joined:29-May 08
  • Location:Australia SA
  • Car:S13

Posted 08 May 2013 - 09:12 AM

 26_S13, on 07 May 2013 - 10:11 PM, said:

Id be more worried about not being able to run a cat becuase of the shape of the tube then abit of ground clearance...

Cat? What the f**k is that haha

#11 STR8E180

  • Joined:30-April 03
  • Location:Australia NSW
  • Car:GTR R34 V-SPEC

Posted 20 October 2013 - 11:23 AM

3inch dump and front

3.5inch cat back

i reckon i could actually go even higher on the cat back

Attached Files



#12 STR8E180

  • Joined:30-April 03
  • Location:Australia NSW
  • Car:GTR R34 V-SPEC

Posted 20 October 2013 - 11:26 AM

 JoELMaN, on 07 May 2013 - 08:35 PM, said:

Does anyone know where I can get hold of some oval tubing and oval to round transitions in Australia? Otherwise I am thinking I will just split a 2" pipe and weld a 50mm flat between them.


thats what i would do

i think 2 inch would be to small i would go 2.5 inch but i would only go oval for the front pipe the cat back half u can tuck up pretty much with out needing to go oval

#13 s13k's

  • Joined:20-August 12
  • Location:Australia NSW
  • Car:180SX Type X

Posted 20 October 2013 - 01:43 PM

If you tuck it up high wouldnt there be a chance it would start rattling off the cars body?

#14 STR8E180

  • Joined:30-April 03
  • Location:Australia NSW
  • Car:GTR R34 V-SPEC

Posted 20 October 2013 - 01:52 PM

 Poppin' fresh, on 20 October 2013 - 01:43 PM, said:

If you tuck it up high wouldnt there be a chance it would start rattling off the cars body?
not if u have brackets holding it in place properly

#15 stevos13

  • Joined:17-May 10
  • Location:Australia QLD
  • Car:s13

Posted 20 October 2013 - 02:17 PM

You could buy some 76mm and flatten it in a press (large industrial press like the types often found in sheet metal workshops). You would find it incredibly difficult to split the pipe and weld in new sheet sections without distortion to some degree, especially if you're not experienced. In other words it would not look neat and would create lots of extra work for an aesthetically poor outcome. In order to retain the same cross-sectional area as 76mm tube you would need to weld in a 49-50mm strip top and bottom. This would be worth it for exhaust tips, but for a full system it seems silly.

From a performance perspective I would assume tube to flow better despite having the same area. I have always believed exhaust gasses flow in a spiral motion, particularly when leaving the turbine housing. Think of it like skulling a beer. If you swirl the bottle while your drinking the beer flows out remarkably quicker. I could see this oval exhaust idea preventing/disrupting flow in that manner. I have not read anything on my theory so I could be wrong, however if it is ground clearance you're after, and your certain you can't tuck a 3" high enough, notching the floor is another out there option.

Stevo.

#16 SILVIA s13

    got milk?.. no milf? well then...GOTTA HAVE 4 DOOR!!

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Posted 21 October 2013 - 03:35 PM

if you oval 3" tube by smacking it your effectively making it a 2.5" for flow

Edited by SILVIA s13, 21 October 2013 - 03:35 PM.


#17 blingcommander

  • Joined:05-October 06
  • Location:Japan
  • Car:Scooty-Puff Jr.

Posted 21 October 2013 - 03:47 PM

3 inch pipe, squashed or not is still going to work out to be 3 inch diameter

#18 JoELMaN

  • Joined:25-October 05
  • Location:Australia NSW

Posted 21 October 2013 - 04:13 PM

 blingcommander, on 21 October 2013 - 03:47 PM, said:

3 inch pipe, squashed or not is still going to work out to be 3 inch diameter
No a squashed pipe will have less cross sectional area

#19 blingcommander

  • Joined:05-October 06
  • Location:Japan
  • Car:Scooty-Puff Jr.

Posted 21 October 2013 - 04:20 PM

doesn't make sense in my brain

#20 (Locky)

  • Joined:23-July 07
  • Location:Australia NSW
  • Car:kouki s14

Posted 21 October 2013 - 04:27 PM

Math
That pie x radius(squared) thing from year 7 so the cross sectional area is different

Let alow flow dynamics and all that shit

#21 JoELMaN

  • Joined:25-October 05
  • Location:Australia NSW

Posted 21 October 2013 - 04:29 PM

The more you squash it the less area it will have. Assume you keep squashing it right down. Eventually the sides will touch and there will be no hole :-P

#22 SILVIA s13

    got milk?.. no milf? well then...GOTTA HAVE 4 DOOR!!

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Posted 21 October 2013 - 04:39 PM

 blingcommander, on 21 October 2013 - 03:47 PM, said:

3 inch pipe, squashed or not is still going to work out to be 3 inch diameter

say you squashed a lil its not going to have much of a change but say you squash it to half the height it will have less volume

#23 blingcommander

  • Joined:05-October 06
  • Location:Japan
  • Car:Scooty-Puff Jr.

Posted 21 October 2013 - 04:41 PM

can someone squash a piece of pipe?

maths can get f**ked haha

#24 stevos13

  • Joined:17-May 10
  • Location:Australia QLD
  • Car:s13

Posted 21 October 2013 - 07:43 PM

You blokes need to sit a maths course. I'm going to pretend I didn't read those above posts. For starters it has nothing to do with volume. Volume is 3 dimensional. And no the cross sectional area of tube or any shape (units2) will not change if you squash it. I suggest you guys ask your parents, they might be able to explain it. In short, are you taking any metal away when changing the shape of the tube??? ponder that.

If someone has done research or has knowledge as to whether round flows better than oval, and by how much I'de be interested to know.

#25 comebackkid

  • Joined:19-January 08
  • Car:96 180sx type x

Posted 21 October 2013 - 08:22 PM

its the same circumference for a 3" tube no matter what shape, but shape may affect flow depending on how squashed it is, like if you flatten it to a 1mm slit it's not going to flow too well.

#26 JoELMaN

  • Joined:25-October 05
  • Location:Australia NSW

Posted 21 October 2013 - 08:26 PM

Surely it was obvious I was talking about the area available for the exhaust gases to flow through, and not the actual metal...

#27 KENut

  • Joined:18-January 11
  • Location:Australia ACT
  • Car:KE70

Posted 21 October 2013 - 08:40 PM

Sup. I reckon oval pipe will flow slightly less than a round tube.

The reason I think this is because of the boundary layer of gas that will adhere to the inner pipe wall surface. As fluid flows through a pipe there is velocity profile across the cross section of the diameter, with higher velocity in the center and slower flow along the wall (since the surface isn't perfectly smooth/frictionless). Boundary layers tend to grow outwards from the pipe wall, and the distance from the wall will correspond to a velocity for a given fluid at a certain temperature.

By changing the geometry you are reducing the area for faster moving gas to flow. You could think of it as the internal friction increasing in the exhaust in a way..

#28 stevos13

  • Joined:17-May 10
  • Location:Australia QLD
  • Car:s13

Posted 21 October 2013 - 08:49 PM

Big sorry fellas, long story short I'm wrong, just sat down with pen and pad and did some calculations. The area does change despite the perimeter staying the same. For any given perimeter a round shape will have a larger area. To have the same cross sectional area as 76mm you will need to weld in the 51.5mm sections top and bottom or alternatively you could squash 90mm (3.5") down to 2 inch height and increase area by approximately 12% above 76mm (3").

#29 JoELMaN

  • Joined:25-October 05
  • Location:Australia NSW

Posted 21 October 2013 - 08:56 PM

Feels like we're going around in circles here, or maybe around in ovals :-P

#30 comebackkid

  • Joined:19-January 08
  • Car:96 180sx type x

Posted 21 October 2013 - 09:09 PM

yeah i just did some calcs too, it seems the area decreases the flatter you go





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