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Location:
Brisbane
Registered:
October 2002
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Re: Back Pressures
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Sat, 22 November 2003 09:27
 
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| oldcorollas wrote on Sat, 22 November 2003 17:44 |
sigh.. well.. i was just going to say the google thing but..
oh, and check out billzilas page, it has a nice graph regarding the lengths. also check out Philip Smiths intake and exhaust book (i thnk it's the scientific design of intake and exhaust systems.
the basic premise is that:
if the reflected negative pressure pulse reaches the exhaust valve just before the valve closes, this negative pressure will help scavenge the exhaust remaining in the cylinder, and will also give a bit of a velocity boost to the incoming fresh charge.
4 into 1 and 4-2-1 extracors work differently, and require different lengths, since with 4-2-1, you have two different reflections, but you are most effectively using 2 seperate pairs of cylinders. 4-1 you have the reflection affecting each of the other cylinders.
for a 4-2-1 tuned for 5500rpm, primary and secondary length may be around 1.25 feet long, with the collector about 2.5 feet long.
it is similar to Helmholtz tuning of intakes, except that for intakes, you want a positive pressure pulse hitting the valve just as it's closing.
how do you think F1 motors reach such high volumetric efficiency? exhaust and intake tuning to effectively give it an NA supercharge 
Philmelvin, you have "Tuned lenght extractors", surely they are tuned to scavenge the cylinders, not give back pressure? not trying to have a go at you, but i don't agree with the back pressure thing 
Cya, Stewart
Cya, Stewart
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well.........that just fucked everything i was taught about exhausts 
edit: i did know about this tho
| Quote: |
if the reflected negative pressure pulse reaches the exhaust valve just before the valve closes, this negative pressure will help scavenge the exhaust remaining in the cylinder, and will also give a bit of a velocity boost to the incoming fresh charge.
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piss-ant attempt to redeem my self 
[Updated on: Sat, 22 November 2003 09:30]
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| | Subject | Poster | Date |
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Back Pressures
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xtigerx | Fri, 21 November 2003 07:34 |
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Re: Back Pressures
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Mr DOHC | Sat, 22 November 2003 02:42 |
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Re: Back Pressures
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oldcorollas | Sat, 22 November 2003 07:16 |
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Re: Back Pressures
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NuGeN | Sat, 22 November 2003 07:29 |
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Re: Back Pressures
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oldcorollas | Sat, 22 November 2003 07:44 |
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Re: Back Pressures
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Mr DOHC | Sat, 22 November 2003 09:27 |
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Re: Back Pressures
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oldcorollas | Sat, 22 November 2003 09:45 |
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Re: Back Pressures
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toof | Sat, 22 November 2003 03:01 |
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Re: Back Pressures
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Mr DOHC | Sat, 22 November 2003 06:15 |
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Re: Back Pressures
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xtigerx | Sat, 22 November 2003 08:10 |
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Re: Back Pressures
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rollawagon | Sat, 22 November 2003 11:43 |
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Re: Back Pressures
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xtigerx | Sun, 23 November 2003 09:00 |
