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JoELMaN

Oval Exhaust System

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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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1298961446_2_FT5343_dsc01069_zpsad0e0b3a.jpg

Edited by JoELMaN

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Cross sectional area compared to tube would be interesting.

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

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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.

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

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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

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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.

 

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.

 

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?

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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

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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

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3inch dump and front

 

3.5inch cat back

 

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

IMG_2245.JPG

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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

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

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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

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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.

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

Edited by SILVIA s13

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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

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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

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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

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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

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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.

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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.

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

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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..

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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").

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

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