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Author
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Topic: exhaust question
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74merc
Gearhead Posts: 956
From: Demopolis AL
Registered: Jun 99
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posted 05-24-2001 12:29 AM
   
got my headers, got a 2 1/4 reducer and 2 1/4 pipe to tie into my existing exhaust.
here's my question.
is my existing 2 or 2 1/8 pipe going to be restrictive and negate the gains of the headers?
what would be effects be of stepping down in size to my smaller pipe?------------------
74 Mercury Comet
302
AOD
3:1
Will the 302 built properly this summer? wish I knew...
http://members.tripod.com/red74merc
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SteveLaRiviere
Administrator Posts: 42859
From: Saco, Maine
Registered: May 99
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posted 05-24-2001 05:52 PM
Not by much. You really won't be turning at a high enough rpm to make much of a difference. {under 5,500, right?}By removing the exhaust manifolds, you are getting rid of most of the restriction. ------------------
'72 Mustang Sprint Coupe 351C 4V/FMX/4.30 Trac Loc
'94 F-150 XL 5.8L/E4OD/3.55 Limited Slip
'97 Probe GTS 2.5L DOHC {Wife's car...}
All Fords since 1977
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Greenstang
Gearhead Posts: 908
From: its all a fog..
Registered: May 2001
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posted 05-24-2001 06:06 PM
...and in theory by reducing the size of the pipe, you will help increase savenging. That is due to the increase in velocity, though I think it would be hard to prove and wouldn't really show much in the real world dyno tests  ...------------------
Marcus
My World
``Two cars hitting the barriers is not an ideal way to finish the first day of practice for a Grand Prix,'' - Patrick Head
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74merc
Gearhead Posts: 956
From: Demopolis AL
Registered: Jun 99
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posted 05-25-2001 12:19 AM
yea, for the time being it'll be under 5500rpms.
planning for around 6500 by the time I'm finished.
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PJHMustang
Journeyman Posts: 35
From: Granada Hills, Ca., USA
Registered: Jan 2001
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posted 05-25-2001 10:58 AM
Once it was common practice by the factory to run say 2" from the engine to the muffler then 1-7/8" from the muffler back. Two reasons given for that practice was quieter operation and the exhaust had cooled so it has a lesser volume requiring a lesser diameter for equal flow.
I would stick with the existing tailpipes until you have the need. It's called economics.
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74merc
Gearhead Posts: 956
From: Demopolis AL
Registered: Jun 99
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posted 05-25-2001 05:26 PM
economics would take over regardless, I was just wondering if it would limit it now or in the near future.
thanks guys.
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richard bohm
Gearhead Posts: 373
From: tucson,az-luray,va
Registered: May 2001
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posted 05-29-2001 02:12 AM
if you have dual pipes already you wont gain much by going to a larger pipe. maybe 10-15 hp. you can make that up by not running the air(you are using the sanden compressor right??). dont bother replacing the pipes untill they need it. then go with 2 1/2" into the mufflers, and 2 1/4" out.
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74merc
Gearhead Posts: 956
From: Demopolis AL
Registered: Jun 99
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posted 05-29-2001 03:24 AM
what are you talking about sanden compressor?
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SteveLaRiviere
Administrator Posts: 42859
From: Saco, Maine
Registered: May 99
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posted 05-29-2001 03:27 PM
Sanden is a type of A/C compresser. ------------------
'70 Mustang Mach 1 351C 4V/FMX/3.50 open {on the way!}
'72 Mustang Sprint Coupe 351C 4V/FMX/4.30 Trac Lok
'94 F-150 XL 5.8L/E4OD/3.55 Limited Slip
'97 Probe GTS 2.5L DOHC {Wife's car...}
All Fords since 1977
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