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post #1 of 6 Old 10-14-2013, 05:43 PM Thread Starter
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Anyone on here a mech. Engineer

I've got a question about flow characteristics of an exhaust idea.
Some guys are hollowing out there DPF so it looks stock. What would it flow like with the downpipe being 4" then going to 8" for a few feet then to dual 4" exhaust with one 4"aero turbine muffler in each of the 4" duals. I've heard the aero turbine's aero foil design helps "pull" or scavenge the exhaust out but would the velocity crash once it hits the 8" section? I've also heard this will make the exhaust sound like stacks without having stacks. That sweet hollow grumble.
The more accurate and scientific the answer the better please.ill attach a crude drawing of what I mean.

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post #2 of 6 Old 10-18-2013, 11:38 PM
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Yep, the velocity drops off as the gas expands into the chamber (which cools it as well) forming what amounts to a gentle 'plug'.

The idea is to keep velocity high without leaving laminar flow.
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post #3 of 6 Old 10-19-2013, 01:22 AM
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you are way over thinking this....

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post #4 of 6 Old 10-19-2013, 01:31 AM
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Quote:
Originally Posted by srt6 View Post
you are way over thinking this....


Matty, I find it funny that you are asking help from random engineers. I am working on a manufacturing engineering degree, and work with a lot of design and mechanical engineers, none of which could help you. You need a fluid dynamics engineer.

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post #5 of 6 Old 10-19-2013, 01:33 AM
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Also, why 8"? Is that the I.D. of the DPF?

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post #6 of 6 Old 10-19-2013, 01:54 AM
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A single 4" exhaust pipe will be good up to ~550bhp. I hate to be the bearer of bad news, but everything from the point that your 4" downpipe connects to the 8" pipe is actually going to be restrictive vs a properly sized exhaust.

Now, if you are going for 'looks and sound' vs actual performance, then you're fine. If you're looking to draw every last bit of power, you're not quite on the right path
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