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#1
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exhaust diameter 101
My friend and i were recently discussing exhaust modifications and the question of increasing the diameter in the exhaust pipes were raised. If one were to replace the entire exhaust system from the headers back, and wished to increase the diameter of the exhaust to 3 in. Would this be possible?
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#2
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Possible yes, but not comming off the manifolds. 2 1/4 is plenty big for a N/A 3.3 anyway.
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92 SVX #772 140k 6speed, ECU Tune stage II, Koni/Ground control, 3,270lbs. 91 Legacy Turbo 5spd. FMIC, crappy stock turbo, ACT clutch. 78 BRAT (New toy) (Soon to be EJ22T powered) 90 240 SX. RB25 powered!! DRIFT!!!111!!! (GF's car) To many cars to spend time on teh web! |
#3
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what is the stock diameter?
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#4
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I ment 2 1/2. I think stock is between 2 1/4 and 2 1/2. Of course I have duel 2 1/4 from the manifold back, that would be like running one 4 1/2 pipe! I think I need a S/C to make it worth it.
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92 SVX #772 140k 6speed, ECU Tune stage II, Koni/Ground control, 3,270lbs. 91 Legacy Turbo 5spd. FMIC, crappy stock turbo, ACT clutch. 78 BRAT (New toy) (Soon to be EJ22T powered) 90 240 SX. RB25 powered!! DRIFT!!!111!!! (GF's car) To many cars to spend time on teh web! |
#5
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From the third cat back, the stock ID is about 60 mm which is about 2.35 inches. For a near stock SVX motor, going up to 2.5" inch ID from the third cat back is a good option. This increases the crosssectional area of the exhaust by 10%.
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Mychailo :: 2006 Silver Mitsubishi Evolution 9, E85, 34 psi peak, 425wtq/505whp DJ :: 1995 Laguna Blue SVX L AWD 5MT (sold) Visit my locker SVX Mods: ND iridium spark plugs, Impreza RS fpr, afr tuned to 13.2:1 using a custom MAF bypass, custom exhaust, WRX 5MT w/ STi RA 1st-4th gear & stock WRX 5th gear, Exedy 13 lb flywheel & Sport Clutch, STi Group N tranny & engine mounts, urethane spacers in rear subframe, rear diff mounts, and pitch stopper, SVX Sport Strut Springs (185f/150r), custom 19 mm rear swaybar, urethane swaybar mounts, Rota Torque 17x8", 225/45-17 Proxes 4 tires, Axxis Deluxe Plus organic brake pads. |
#6
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Yea, that is a good idea... going to 3 inches though on a N/A car just isn't really nessasary.... You'll probably get a big Hp increase up around Redline but you will loose so much torque down low it won't even be funny.....
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2020 Subaru Outback Touring - Wife's first Subaru 2005 Volvo V70R - 5-cylinder love! :Heart: ** SOLD **1998 Subaru Legacy 2.5GT Wagon - MOST RELIABLE car I've ever owned ** SOLD **2006Subaru WRXSTi (Former "Boxer4Racing.com / Continential Tire" STi) - Built EJ22t block / EJ207 JDM STi "big port heads" - 9,000rpm MONEY PIT!!! ** SOLD ** 1995 "Tree-Hugger Green" SVX L AWD(5 MT) --- "Gumby" 130K miles #399 in MY95, my original love... |
#7
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3" is probably fine for the 3.3l
considering that 2.25 is optimal for the 2.2l that this is based off of and 2.5 is optimal for the 2.5l engine you might wanna try 2.75 tho everyone always jumps from 2.5 to 3
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SV What? |
#8
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Quote:
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Mychailo :: 2006 Silver Mitsubishi Evolution 9, E85, 34 psi peak, 425wtq/505whp DJ :: 1995 Laguna Blue SVX L AWD 5MT (sold) Visit my locker SVX Mods: ND iridium spark plugs, Impreza RS fpr, afr tuned to 13.2:1 using a custom MAF bypass, custom exhaust, WRX 5MT w/ STi RA 1st-4th gear & stock WRX 5th gear, Exedy 13 lb flywheel & Sport Clutch, STi Group N tranny & engine mounts, urethane spacers in rear subframe, rear diff mounts, and pitch stopper, SVX Sport Strut Springs (185f/150r), custom 19 mm rear swaybar, urethane swaybar mounts, Rota Torque 17x8", 225/45-17 Proxes 4 tires, Axxis Deluxe Plus organic brake pads. |
#9
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Quote:
A single pipe equivalent to a dual 2 1/4 exhaust would have a diameter of approx 3 3/16.
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David B. SVXipedia @ SVX-IW.COM -- SVX Information Warehouse 2.0 coming...eventually! Ebony 1992 SVX LS-L 5 spd Koni/GC Stebro 187k miles RIP (Rust In Pieces) 1993 SVX 5 spd Koni/GC Stebro Polyurethane bushings still available! |
#10
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Quote:
phil
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~Phil Teal 1992 Subaru SVX Turbo - Sold in May 2011 to peace-frog. |
#11
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Quote:
I never was any good in math
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92 SVX #772 140k 6speed, ECU Tune stage II, Koni/Ground control, 3,270lbs. 91 Legacy Turbo 5spd. FMIC, crappy stock turbo, ACT clutch. 78 BRAT (New toy) (Soon to be EJ22T powered) 90 240 SX. RB25 powered!! DRIFT!!!111!!! (GF's car) To many cars to spend time on teh web! |
#12
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Quote:
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Matt Locker Link 2015 BRZ Limited 6MT 92 Ebony LS-L ECUtune Stage2av1, Z32 MAF, 370cc injectors, TomsSVX intake, BontragerWorks 22mm RSB #003, HID Hi and Lo beams, OT endlink and bushing mods, PWR Aluminum radiator, Harvey's QC shift kit, 2.5" flowmaster 80 exhaust, 17" Michelin Pilot Sport A/S, Poly sway bar bushings, Slotted Bradi rotors, AFBeefcake powdercoated calipers, 97 grill, and a huge set of air horns. 300,000 miles and counting 92 Ebony LS-L. ecutune stage1v4, motorsport 1pc pulley. Garage Queen - sold to Dad in upstate NY 155,000 miles 19 Subaru Ascent Premium - -Hers !. 89 DL 4x4 little red wagon - a.k.a. The immortal suby. 275k R.I.P. |
#13
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[QUOTE]Originally posted by Phast SVX
[B] ive run open headers at hte track(uniongrove, w/o nitrous) and recieved a .1 second increase. I reset and let hte ecu learn to the gas station and back(15 miles) There is virtually no restriction in our exhuast, and it seems to be give here take there. Phil, Possibly the 0.1 second resulted from practice gained as a result of the previous runs ! On second thoughts I am not sure if you by "increase" you mean an improvement or a longer elapsed time and therefore decrease in performance!? In any event, the above should be shouted out loud from the roof tops, included in the How Too section as a "How Not Too" and posted in Mod Mania for good measure. I have always been confident that the stock exhaust system is obviously well designed and is in fact a carefully tuned system and that anything fitted by an aftermarket exhaust shop will be an absolute downgrade. Congratulations, Trevor
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! |
#14
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open headers is not as good as running a straight pipe. cut your exhaust off at the axle... then test it out...
with open headers you will loose the scavenging effect and all of the exhaust gasses will not be pulled from the engine in time for the intake stroke and exhaust gasses will be pulled into the combustion chamber... there is less oxygen in exhaust gasses than in air.. duh... this will hurt performance back pressure is bad yes... but exhaust flow velocity for scavenging is very very important
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SV What? |
#15
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I agree absoutely and what is explained illustrates why the original system works so well. It has been designed accordingly after a great deal of practical testing to an extent beyond the capability of any after market exhaust shop. What is more it is obvious that the original design has not been compromised on the basis of cost.
A properly tuned straight pipe system would result in improvement but as it is not possible to run one on the road, the comparison with open short pipes is valid.
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! |
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