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Location:
Sydney
Registered:
April 2003
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 Back Pressures
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Fri, 21 November 2003 07:34
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Can anyone please clarify this....
Turbo cars: best exhaust would be a straight through, hi flow system.
N/A: best exhaust would be not TOO big, say for a 1ZZ-FE. max would be 2 1/4". straight through is NOT good because n/a require back pressure. the difference between press and mandrel, is it noticeable on a n/a?
Can anyone clarify this???????
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Location:
Brisbane
Registered:
October 2002
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Re: Back Pressures
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Sat, 22 November 2003 02:42
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engines need back pressure to work better, the reasont turbo cars need a huge zorst is cause its best not to have back pressure AFTER the turbo cause it'll just "choke" the turbo, the turbine acts as the back pressure for the engine
what cc is a 1zzfe
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Location:
Newcastle
Registered:
July 2003
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Re: Back Pressures
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Sat, 22 November 2003 03:01
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1800cc iirc ?
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Location:
Brisbane
Registered:
October 2002
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Re: Back Pressures
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Sat, 22 November 2003 06:15
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2.25 would be ok, since they rev so hard.
if they didnt have vvti itd only need 2.0 i reckon
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Back Pressures
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Sat, 22 November 2003 07:16
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LOl, back pressure 
my 4K goes rather nicely with 2".
the velocity of the turbine benefits from having a higher pressure drop across the turbo. this allows more expansion after the turbine.
backpressure helps if you have a V8 with 300deg cams, since you need backpressure to keep the intake charge IN the cylinder 
if you choose your cam right, backpressure has no benefit.
resonance tuned exhaust manifold on the other hand......
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Location:
Adelaide
Registered:
April 2003
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Re: Back Pressures
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Sat, 22 November 2003 07:29
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| oldcorollas wrote on Sat, 22 November 2003 17:46 |
resonance tuned exhaust manifold on the other hand......
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Care to elaborate...?
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Back Pressures
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Sat, 22 November 2003 07:44
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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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Location:
Sydney
Registered:
April 2003
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Re: Back Pressures
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Sat, 22 November 2003 08:10
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1zz-fe is a 1800cc
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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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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Back Pressures
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Sat, 22 November 2003 09:45
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Author: Smith, Philip H. (Philip Hubert), 1906-
Title : The scientific design of exhaust and intake systems / by Philip H. Smith, in collaboration with John C. Morrison.
Edition 3d ed.
Publication Details : Cambridge, Mass. : R. Bentley, 1971.
Format : Book
Description : 274 p. : ill. ; 22 cm.
ISBN 0837603099
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Location:
sunshine coast
Registered:
November 2003
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Re: Back Pressures
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Sat, 22 November 2003 11:43
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turbo cars is best to go mandrel of the turbo to cat or first muffler, unless you are doing big revs press bent is sufficent for the extra money you pay on mandrel only marginal gain unless doing big revs.just make sure you get good mufflers that flow.
JAZE
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Location:
Sydney
Registered:
April 2003
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Re: Back Pressures
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Sun, 23 November 2003 09:00
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well, i got a high flow cat and full Lukey system.
Lukey is pretty good, right?
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