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Old 03-27-2003, 02:50 AM   #1
wistful
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Default brilliant exhaust idea =)

well.. not really.. but I have a question for you physics majors out there.

I was studying for my physiology final today, and it deals with flow issues (arteries and stuff..) In any case.. Pousille's law came up. which basically says that resistance is inversely related to radius of a pipe to the four power... more importantly.. AND directly proportional to length. THEREFORE... instead.. or in addition to at least, making our exhausts increase in diameter from 1.75" to 2.25"... could we NOT decrease the length of our pipes... have it come out right behind the front wheel. This way, we still have scavenging, high velocity speed, yet a great decrease in resistance. The only thing I haven't thought abuot is packaging. Howz it sound so far though?

Don
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Last edited by wistful; 03-27-2003 at 07:10 PM.
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Old 03-27-2003, 02:52 AM   #2
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sounds loud but i really have no idea
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Old 03-27-2003, 08:45 AM   #3
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Default Testing

Wanna test it out?

Poiseuille's Law Calculation

I know nothing about this stuff but what it appears to be is that this law only applies to liquids, not gas. I think it has something to do with smooth flow (Laminar) vs turbulent flow (air) and the law only applying to Laminar flow.

Last edited by Kevin Thomas; 03-27-2003 at 08:50 AM.
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Old 03-27-2003, 08:53 AM   #4
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Exhaust gasses are anything but laminar flow.

There may be some gain to shortening the pipes a little.....but I don't think you would want to dump it out right behind the front wheel......maybe mid way back or right before the rear wheel......I can't say you'd get any noticable gains compared to a system that is the same size and goes all the way to the rear.
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Old 03-27-2003, 09:17 AM   #5
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yea.. thatll be just a tiny bit loud
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Old 03-27-2003, 09:22 AM   #6
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mmm... side exaust...

that'd be kewl! It doesn't have to be loud... you can still have a muffler... You just got to fit it somewhere...
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Old 03-27-2003, 12:32 PM   #7
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Not to mention you would probably die of Carbon Monoxide poisoning
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Old 03-27-2003, 12:34 PM   #8
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Quote:
Originally posted by Eric v2.1
Not to mention you would probably die of Carbon Monoxide poisoning
nah... tons of cars do it...
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Old 03-27-2003, 12:43 PM   #9
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I always thought about remounting the fuel "black box" in the trunk and running duels out the rear.
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Old 03-27-2003, 01:09 PM   #10
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Also remember some of the SCCA classes have the rule that the exhaust "must be quiet and terminate behind the driver".

Anybody have that pic of the Impreza with side exit exhaust that came through a cutout in the side skirts? I like that pic.

Shane -- http://www.warpthree.com
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Old 03-27-2003, 01:39 PM   #11
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Quote:
Originally posted by DanzBorin
nah... tons of cars do it...
tons huh? name 3 DOT approved cars that do do this.
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Old 03-27-2003, 01:50 PM   #12
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The Viper..............the Cobra R...........1979 Dodge Lil Red Express.
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Old 03-27-2003, 02:21 PM   #13
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Quote:
Originally posted by Puckaveli
The Viper..............the Cobra R...........1979 Dodge Lil Red Express.
rouch mustangs v6 and v8
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Old 03-27-2003, 05:08 PM   #14
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None of those cars have exhaust that come out right behind the front wheel. All of them come out near the back wheel. DOT rules state that the exhaust must exit behind the pasenger compartment. This is to prevent carbon monoxide poisioning. Even if you did put a muffler that close to the motor you would still lose power, the most efficent place for a muffler is as far away from the engine as possible (for the origional post.)
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Old 03-27-2003, 07:22 PM   #15
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Quote:
Originally posted by DanzBorin
mmm... side exaust...

that'd be kewl! It doesn't have to be loud... you can still have a muffler... You just got to fit it somewhere...
We were talking about side exhaust period.
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Old 03-27-2003, 08:00 PM   #16
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DOT also states a lot of things that we don't really do. Hollowed cats, lightweight beams, etc, etc.

hehehe:
http://www.exvitermini.com/pics/1506llf.jpg

Don
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Old 03-27-2003, 08:28 PM   #17
Eric SS
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Quote:
Originally posted by SIXGUNZ
DOT rules state that the exhaust must exit behind the pasenger compartment. This is to prevent carbon monoxide poisioning. Even if you did put a muffler that close to the motor you would still lose power, the most efficent place for a muffler is as far away from the engine as possible (for the origional post.)
The point I was getting at
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Old 04-03-2003, 08:29 AM   #18
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Formula posted at beginning of thread will work because a gas is a liquid and behaves the same way in terms of laminar flow as an uncrompressable fluid.
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Old 04-04-2003, 07:56 AM   #19
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Of course, that formula is for a perfect world. We have many other things to take into account, such as the smoothness of the inside of the exhaust (needed for laminar flow) and the fact that our exhaust pulses (which I have no idea how to compensate for). I know a Physics professor that would kill me for making him think about this
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Old 04-05-2003, 01:11 AM   #20
Andrew
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just use an exhaust cutout
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Old 04-05-2003, 02:39 AM   #21
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Coincidentally, after hearing Kostamojen's straight pipe first hand, I decided that would be nifty on my RS... then I figured, why not do a side pipe in front of the driver's side rear wheel? I'm very much leaning towards it, since it's only about a $75 pipe...
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