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Discussion Starter · #1 ·
I am not sure if this has been covered before or not, but I have an idea.

Usually you make power with an exahust with least restrictions and the fastest velocity. Gases are hottest at the header and gradually cool down by the time they leave the exahust tip. Hot gases move faster than cooler gases because the molecules are more excited and hence the foundation of my theory. The only way you can keep the same velocity is shrink the piping.

Start out with a 3" header collector then gradually go down to something like 2.5". I know that it is hard to go down "gradually" but something like 3-->2.75-->2.5.

Any comments guys?
 

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Memento Mori
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airspeed is a tricky bitch

heat wrap your exhaust is the easiest solution, but as the air cools it gets more dense, so a 3" with a hot gas is less restrictive then a 3" with a cooler gas, so if anything go bigger, BUT a quick transition is going to hurt you, you'd preferably want to megaphone from the header to the exhaust tip
 

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Discussion Starter · #5 ·
I think those two things work against one another.
You are right, but at a certain point in your exhaust the benefit of higher velocity just might overcome the addition of the restriction.

...or stop the gasses from cooling as quickly. 8)
Ya, just run open header :tounge2:.

airspeed is a tricky bitch

heat wrap your exhaust is the easiest solution, but as the air cools it gets more dense, so a 3" with a hot gas is less restrictive then a 3" with a cooler gas, so if anything go bigger, BUT a quick transition is going to hurt you, you'd preferably want to megaphone from the header to the exhaust tip
I understand that colder gases are denser than hotter gases which leads to the following point: wouldn't the gases in a 3" piping be harder to push because it is "heavier" (higher volume and high density) than for instance a 2.5" piping (lower volume and high density)?

If I could just find out the pressure that the gas exists each piston then I could do some mass/energy balance to see if my idea works :(.

I might try this idea out when I redo my exhaust. I am thinking this will provide better low end torque fo sho.
 

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i say just stick 3in and heat wrap the bitch... of course the easiest way is just to run an open header but you cant do that on a street driven car
 

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i don't think itll make a big difference. because you can blow through a normal straw easily; The air from your mouth will cool as they move through the straw. If you had a straw that got smaller towards the end, i would think it would be a little harder to blow. Even though the air would cool towards the end.
 

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Discussion Starter · #11 ·
you should ask steve about his feelings of bigger exhausts now....

:)
Who is Steve?

i don't think itll make a big difference. because you can blow through a normal straw easily; The air from your mouth will cool as they move through the straw. If you had a straw that got smaller towards the end, i would think it would be a little harder to blow. Even though the air would cool towards the end.

I give up. Just get a 3" and call it a day.
 

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Good reason to put the muffler at the back of the car.
 

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Oh great, not another one of these threads. I think I got my feel of BS in my thead.
yeah i thought it was gonna be the same thing but his theory was diff from what that thread was talkin about
 

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But but but, you hurt my feelings :(.

Ok...not to be like that or anything but i'm just saying if you look at honda's sport bikes which are essentially a high perfomance inline four. Their exhausts do the opposite of what you are talking about they use a step design but it is step up say from 2''-2.25''-2.5'' before the muffler. Now these are basically race bikes and the motors are designed to make power in the upper r's. I have to feel like the theory is similar.
 

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yes you could on too something up there
but bikes also have much less lenght in exhaust piping

also what do all motor drag cars run
they run open header
open header=the best exhaust
just might be kinda loud
 

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Discussion Starter · #19 ·
I have finally decided to run a 3" header collector to an exhaust-cutout followed by 2.5" cat & resonator (b/c I already have it :p ) then a small portion of 2" piping in the end.

And my exhaust will end before the first 90 degree bend like 98vtec's exhaust.
 
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