Oval pipe flow as good as round?
TECH Addict
Joined: Feb 2012
Posts: 2,103
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I have one question, is your build THAT high end to where you are worried about the flow difference between oval and round??? On a average joe budget I bet not.
That being said, make sure the oval pipe as same cross section as a round pipe you would like to use and utilize it for ground clearance reasons.
I like that NASCAR comment...those motors are a little more expensive and put out a little more power than that you have in our street driven cars lol
I want oval JUST for ground clearance reasons. Power gain/loss will negligible.
That being said, make sure the oval pipe as same cross section as a round pipe you would like to use and utilize it for ground clearance reasons.
I like that NASCAR comment...those motors are a little more expensive and put out a little more power than that you have in our street driven cars lol
I want oval JUST for ground clearance reasons. Power gain/loss will negligible.
TECH Enthusiast
Joined: Jun 2005
Posts: 546
Likes: 0
From: Wichita, KS
Interesting topic.
Does anyone on this forum actually have oval exhaust? I would love to explore the possibility of an oval x-pipe going to dumps. The inch of ground clearance would be worth it to me.
Does anyone on this forum actually have oval exhaust? I would love to explore the possibility of an oval x-pipe going to dumps. The inch of ground clearance would be worth it to me.
You cant calculate flow like that. Different engines with better or worse efficiency will affect the way exhaust flows. If you were pumping water through it maybe but on exhaust not so much. If that were the case everybody hog out their exhaust ports as big as possible to flow more! Nooo... shape does matter
I still think oval with same overall area will outflow perfectly round due to velocity. I would bet one of my nutz its not the other way around. I hope somebody doesn't prove me wrong lol
I still think oval with same overall area will outflow perfectly round due to velocity. I would bet one of my nutz its not the other way around. I hope somebody doesn't prove me wrong lol
TECH Addict
Joined: Feb 2012
Posts: 2,103
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All you need to do is simple math to figure out the height of the oval pipe you want to get you 1" more clearance.
Teching In
Joined: Dec 2013
Posts: 7
Likes: 0
From: Cincinnati, OH
To put it in simpler terms:
For steady flow calculations, an equivalent diameter is used called Hydraulic diameter.
This is equal to 4 x Area / perimeter.
If you take a round 16 ga. exhaust pipe and form it into a 2:1 ratio ellipse then outside dimensions and equivalent inside diameter are as follows:
4" Pipe OD ==> 5.2" X 2.6" ==> 3.2" equivalent ID
3 1/2" Pipe OD ==> 4.5" X 2.25" ==> 2.8" equivalent ID
3" Pipe OD ==> 3.9" X 1.95" ==> 2.4" equivalent ID
2 1/2" Pipe OD ==> 3 1/4" X 1 5/8" ==> 2" equivalent ID
If you squash it more to make a 2.67:1 ratio ellipse (like a "Blue Oval") you get the following:
4" Pipe OD ==> 5.5" X 2.1" ==> 2.7" equivalent ID
3 1/2" Pipe OD ==> 4.8" X 1.8" ==> 2.4" equivalent ID
3" Pipe OD ==> 4.1" X 1.6" ==> 2" equivalent ID
2 1/2" Pipe OD ==> 3.5" X 1.3" ==> 1.6" equivalent ID
There are valid arguments that can be made against how applicable this, however it may give some perspective to those looking for ground clearance.
For steady flow calculations, an equivalent diameter is used called Hydraulic diameter.
This is equal to 4 x Area / perimeter.
If you take a round 16 ga. exhaust pipe and form it into a 2:1 ratio ellipse then outside dimensions and equivalent inside diameter are as follows:
4" Pipe OD ==> 5.2" X 2.6" ==> 3.2" equivalent ID
3 1/2" Pipe OD ==> 4.5" X 2.25" ==> 2.8" equivalent ID
3" Pipe OD ==> 3.9" X 1.95" ==> 2.4" equivalent ID
2 1/2" Pipe OD ==> 3 1/4" X 1 5/8" ==> 2" equivalent ID
If you squash it more to make a 2.67:1 ratio ellipse (like a "Blue Oval") you get the following:
4" Pipe OD ==> 5.5" X 2.1" ==> 2.7" equivalent ID
3 1/2" Pipe OD ==> 4.8" X 1.8" ==> 2.4" equivalent ID
3" Pipe OD ==> 4.1" X 1.6" ==> 2" equivalent ID
2 1/2" Pipe OD ==> 3.5" X 1.3" ==> 1.6" equivalent ID
There are valid arguments that can be made against how applicable this, however it may give some perspective to those looking for ground clearance.
TECH Resident
Joined: Apr 2014
Posts: 985
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Staging Lane
Joined: Oct 2003
Posts: 52
Likes: 0
Pipe flow May not matter at street power levels, but the resistance to flow thru a pipe depends on 3 things: Cross sectional area, (wetted) circumference of the pipe, and the internal finish of the surface. (all this is based on straight sections, bends are a bunch of new effects).
In general, circular pipe has the most cross sectional area for a given circumference, so it flows the best. If you have to flatten pipes to an oval, you need to start with a larger diameter pipe to get the cross sectional area up. The added area works to counteract the higher circumference.
In general, circular pipe has the most cross sectional area for a given circumference, so it flows the best. If you have to flatten pipes to an oval, you need to start with a larger diameter pipe to get the cross sectional area up. The added area works to counteract the higher circumference.
Teching In
Joined: Jan 2016
Posts: 1
Likes: 0
So, this was an old thread but I thought this would be interesting to the topic at hand as they did, in essence, oval the pipes.. As they say, proof is in the pudding:
https://www.youtube.com/watch?v=azPK...ature=youtu.be
https://www.youtube.com/watch?v=azPK...ature=youtu.be
