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Author
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Topic: Got a question about exhaust
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BLstangin
Gearhead Posts: 779
From: St. James, MN
Registered: Apr 2002
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posted 02-04-2005 12:51 PM
   
O.k. on my 302 I'm going to be running 2.5" pro street spintechs and the 2.5" mandrel bent flowmaster tailpipes. My header collectors are 3" It would be rather inexpensive for me to make an x-pipe out of 3" as I can get access to it cheaply. Would it hurt anything to make the pipe going from the collector, the x-pipe, and the pipe running to the mufflers 3" Will this kill the motor in any way or won't it know the diff because it goes to 2.5" at the mufflers? My combo
306,
kb dome pistons
10.3:1 compression ratio
DOOE-C casting windsor heads ported,
hydro roller 230-232 @.050, .550 lift, 110 lsa.
weiand stealth intake
650 dp
flowtech headers
4-speed
3.50 or 4.11 locker rear
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1970 coupe restored with the help of my dad. 306 with 650 dp holley, Weiand Stealth intake, headers, mme custom roller cam, harland sharp roller rockers, kb pistons, 10.3:1 compression ratio, pertonix ignitor 2 with matched coil, lakewood bellhousing, 4-speed toploader, and 3.50 9" locker rear.
1986 f-150, 5.0, factory towing package with original c-6 trans
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grego37
Gearhead Posts: 132
From: los angeles,CA,USA
Registered: May 2004
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posted 02-04-2005 02:53 PM
What I found out from talking to different exhaust companies,The only time you should step up to 3" pipe is if you're over 500 HP .Or buzzing from 5000 to 10000 RPM all day.
You'd actually hurt your performance if you did so. It would kill your entire bottom end performance.
Id stick with the 2 1/2"
good luck.
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Bloose
Gearhead Posts: 621
From: Milwaukee, WI
Registered: Dec 2001
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posted 02-04-2005 08:39 PM
One of the car mags did a dyno test of different exhaust setups on a 5.0L. The optimum set up they found was a 3" into a 3" x pipe then 2.5" after the x to 2.5" mufflers. That made the most torque and HP. The problem is not all of us have all day access to a dyno and unlimited exhaust pipe options, so you just never know.Anyone ever chassis dyno a setup with open headers and then full exhuast to see if you really lost low end torque? Seems sort of dumb but I'm wondering how running a more free flowing exhast would hurt you. I know about scavaging but I thought most of that would take place very close to the collector. I though this is why running a short pipe after the collector was better than just open collectors. I know I read somewhere that better flowing exhaust was always better, period. I just don't know what the truth is? B-loose
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Fastymz
Moderator Posts: 18703
From: Reno Nv USA MEM#1240
Registered: Apr 2001
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posted 02-04-2005 08:44 PM
quote:
Originally posted by Bloose:
. I know I read somewhere that better flowing exhaust was always better, period. I just don't know what the truth is?B-loose
Alex put it best. Go to track make a few runs with the exhaust system hooked up, and make a few runs with open headers. If you pick up ET then your system is restrictive. I've read many times that a 3" system to the mufflers is all you need.The best system will give you the same runs with it hooked up or not. ------------------
oddly obsessed with big scoops on little Mustangs 65 coupe 351w C4 Big Boss 429 hood scoop,8" 3.40 TracLoc. My Pics [This message has been edited by Fastymz (edited 02-04-2005).]
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74merc
Gearhead Posts: 1006
From: Demopolis AL
Registered: Jun 99
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posted 02-05-2005 01:33 AM
quote:
Originally posted by Bloose:
One of the car mags did a dyno test of different exhaust setups on a 5.0L. The optimum set up they found was a 3" into a 3" x pipe then 2.5" after the x to 2.5" mufflers. That made the most torque and HP. The problem is not all of us have all day access to a dyno and unlimited exhaust pipe options, so you just never know.Anyone ever chassis dyno a setup with open headers and then full exhuast to see if you really lost low end torque? Seems sort of dumb but I'm wondering how running a more free flowing exhast would hurt you. I know about scavaging but I thought most of that would take place very close to the collector. I though this is why running a short pipe after the collector was better than just open collectors. I know I read somewhere that better flowing exhaust was always better, period. I just don't know what the truth is? B-loose
the velocity of the exhaust flowing through the pipes helps draw the exhaust out, and can help with intake as well during overlap. The exhaust is just like everything else, it needs to be tuned for whatever setup it will be on.
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BLstangin
Gearhead Posts: 779
From: St. James, MN
Registered: Apr 2002
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posted 02-05-2005 11:13 AM
O..k thanks for the advice guys, so should I just run it with 3" to the mufflers, and 2.5 mufflers and 2.5 tailpipes? I'm thinking it won't hurt me to much as I'm still resticting it to 2.5 before the end. Alex do you have an opinion on this?------------------
1970 coupe restored with the help of my dad. 306 with 650 dp holley, Weiand Stealth intake, headers, mme custom roller cam, harland sharp roller rockers, kb pistons, 10.3:1 compression ratio, pertonix ignitor 2 with matched coil, lakewood bellhousing, 4-speed toploader, and 3.50 9" locker rear.
1986 f-150, 5.0, factory towing package with original c-6 trans
IP: Logged |
bluestreek
Gearhead Posts: 1724
From: Athens,GA
Registered: Jul 2001
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posted 02-05-2005 03:35 PM
Those mag articles only concentrate on "peak" torque and HP. Those benefits are only usable at WOT on a car that can take full advantage of the peak rpm range at a race track. If you go too big on your exhaust, you will definately feel and hear a difference at normal driving speeds. It'll be louder and less torquey. It's just like anything else you do to to a steet car. You have to reach a compromise. The 3" x-pipe may be ok but 2.5" exhaust is more than enough for a little 302 unless you plan on adding N2O or forced induction. ------------------
1966 Mustang Coupe: Custom glass hood and BIG scoop sits atop a 289 stroked to 331 c.i., Steel crank, rods and girdle, TFS alum. heads, Stealth 8020 intake, Xtreme 268 Solid Roller, Holley 750 HP, long tubes, 4speed, 9" 3.50 posi.
11.50 @ 116 mph (7.33 @ 93 mph)daily driver!
DanH
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Fastymz
Moderator Posts: 18703
From: Reno Nv USA MEM#1240
Registered: Apr 2001
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posted 02-05-2005 04:48 PM
Dan, where would the HP cut off be ?
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oddly obsessed with big scoops on little Mustangs 65 coupe 351w C4 Big Boss 429 hood scoop,8" 3.40 TracLoc. My Pics
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bluestreek
Gearhead Posts: 1724
From: Athens,GA
Registered: Jul 2001
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posted 02-06-2005 01:15 AM
The torque loss can usually be felt from off idle to about 2800 rpms. The header collectors seem to like a slight restriction just down stream. After that it doesn't matter.------------------
1966 Mustang Coupe: Custom glass hood and BIG scoop sits atop a 289 stroked to 331 c.i., Steel crank, rods and girdle, TFS alum. heads, Stealth 8020 intake, Xtreme 268 Solid Roller, Holley 750 HP, long tubes, 4speed, 9" 3.50 posi.
11.50 @ 116 mph (7.33 @ 93 mph)daily driver!
DanH
IP: Logged | |
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