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opinions on straight pipes

5K views 27 replies 12 participants last post by  ThePrimerSuspect 
#1 ·
Car is a 91 xr7 5.0. I have a couple options, just want to see what people who have similar setups think. I was thinking catless true dual straight pipes. Or catless dual-in dual-out flowmaster where the y pipe is. Not trying to run cats, I don't drive the car enough for it to matter. My 88 has catless h-pipe into flowmaster 40 dumps and it sounds awesome
 
#4 ·
Straight pipes with no mufflers are for broke high school kids who cant afford real exhaust. I vote flowmasters they sound great on 5.0s
 
#5 ·
depends on what sond you want. raspy sound?? flowmaster. deep rumble?? magnaflow or a cheaper version thats just as good is thrush. dont staight pipe it you lose back pressure and annoy people lol
 
#7 ·
it all depend on your tastes i did the same thing. cut the old mufflers off the bird to see how it sounds an it sounded good but it sounded better with the thrushes so i put em on. id say try it cut off and see and if not get some mufflers.
 
#10 ·
My 95 is catless with a magnaflow tru-x x-pipe and straight pipes all the way back to the bumper. IMO it sounds great when you get on it and like crap when you let off the gas, it pops/crackles, and it's very raspy. I want to put mufflers on it but the current primary driver. My mother (midlife crisis much?) loves the way it sounds. I can't stand it.
 
#11 ·
A couple of FYI's

1. Removing the cats will really not gain much power.
2. Even though you are exempt from inspections, you are not exempt from the requirement to have them- even US Fish & Game Wardens carry a manual that identifies each vehicle and the required smog equipment, illegal engines changes, etc with pics of how to ID.
3. Any law enforcement officer (including fish & game), EPA inspector, etc. can impound the vehicle and cite it as a gross pollutor
4. Once cited, a judge will decide if the vehicle is to be scrapped or returned to the owner- and you do not have any opportunity to speak in court- just required to sit 7 listen.
5. if the vehicle is returned- guess what, now you have to repir and take the vehicle to a federal referee station for the rest of "it's life" for a smog inspection & test.

IMHO, it's not worth the risk versus the little gain. Ok, now for muffler info....


broaderperformance.com/muffler_flow_tests.htm (Independently tested cfm flows of the more popular mufflers, glasspacks and resonators @ 15” wc:
2 ½” diameter straight pipe 521
2 ¼” diameter straight pipe 365
2” diameter straight pipe 283
2 ¼” diameter tailpipe 268
2 ¼” round glasspack- no louvers 274
2 ¼” round glasspack- with inward punched louvers 133
2 ¼” round glasspack- inward punched louvers/installed backwards 141
2 ½” inlet/outlet Dynomax SuperTurbo 268
2 1/4” inlet/outlet Thrush CVX 260
2 ½” inlet/outlet Flowmaster 2-chamber 249
2 ¼” inlet/2 ½”outlet Cherry Bomb turbo 249
2 ¼” inlet/outlet Flowmaster 3-chamber 229
2 ¼” inlet/2 ½”outlet Maremount Super C (OEM Replacement) 149
2 ¼” inlet/2” dual outlet Maremount 183
2 ¼” inlet/outlet California Turbo 229
2 ½” inlet/outlet Hooker Aerochamber 324
2 ½” inlet/outlet Hooker MaxFlow 521
2 ¼” inlet/outlet Maremount Cherrybomb Vortex 298
2 ½” inlet center/outlet offset Borla Turbo 373


http://www.popularhotrodding.com/eng...../index1.html (this is an in-depth article that tests not only the mis-conception of flow demand but also how placement of a muffler (a glass pack in this dyno test) can actually "fool " the system into thinking that it is essentially a straight pipe.




I have listed here a muffler shootout test done by CAR CRAFT:

The Mufflers
MAKE MODEL Part No. COST
SUMMIT Turbo 630125 $14.75
THRUSH Magnum Glasspack 24214 $16.50
THRUSH Boss Turbo 17718 $23.95
HOOKER Competition 21006 $25.95
DYNOMAX Super Turbo 17733 $28.50
DYNOMAX Race Magnum 24215 $31.95
HOOKER Super Competition 21106 $35.95
SUMMIT Fully Welded 630325 $38.69
FLOWTECH Afterburner 50322 $39.95

MUFFLER FLOW TEST

MUFFLER Flow at 28-in H20
DynoMax Race Magnum 528.64 cfm
Thrush Magnum Glasspack 507.40 cfm
Summit Fully Welded 343.38 cfm
Flowtech Afterburner 342.20 cfm
DynoMax Super Turbo 333.94 cfm
Hooker Competition 232.46 cfm
Hooker Super Competition 320.96 cfm
Summit Turbo 331.16 cfm
Thrush Boss Turbo 297.36 cfm

MUFFLER Idle dB WOT dB
DynoMax Super Turbo 89 123
DynoMax Race Magnum 94 133
Flowtech Afterburner 92 124
Hooker Competion 92 122
Hooker Super Competion 90 125
Summit Turbo 89 124
Summit Fully Welded 92 125
Thrush Boss Turbo 90 123
Thrush Magnum Glasspack 92 128

DYNO TEST
All mufflers were dyno-tested on a 355-cube SBC with 10.0:1 compression, Air Flow Research 190 aluminum heads, a CompCams 292 hyd. a Victor Jr. intake, a Holley 750-cfm double-pumper, and 1 5/8 Headman headers.


MUFFLER HP TORQUE 2,500-6,000rpmAverage
Hooker Competition 397.4 381.1 286.8hp/351.9 lb-ft
Thrush Boss Turbo 407.1 384.9 292.1 hp/357.5 lb-ft
DynoMax Race Magnum 409.5 394.3 298.8 hp/366.9 lb-ft
Flowtech Afterburner 409.7 391.2 294.8 hp/361.7 lb-ft
Thrush Glasspack 409.5 389.8 297.7 hp/365.3 lb-ft
Summit Turbo 411.5 386.3 291.5 hp/357.4 lb-ft
DynoMax Super Turbo 412.7 387.2 292.6 hp/358.6 lb-ft
Hooker Super Comp 413.8 387.2 292.8 hp/359.0 lb-ft
Summit Fully Welded 415.4 390.7 295.6 hp/362.4 lb-ft

While there are mufflers that will out flow a glass pack design, it also depends on the design. Does the glasspack use "louvers or perforations" - Louvers reduce the flow by as much as 50% but Allied resonators (that sell for $20-$40) each and available at any muffler shop) installed backwards in independent test flowed 90%+ of a "race spec muffler". Others using other brands consistantly showed similar results.
 
#12 ·
Waaaaayyy too much info dude. I appreciate the effort, but I'm not looking for a race car. I already got one. I just want some decent sound out of it. As far as the penalties, I'm well aware. But where I'm at its never enforced. And I mean NEVER. I have never heard of anyone having a problem with law enforcement or fish and game or whoever, for not having cats. Anytime I ever got stopped in my 88 they always just ask me what's done to it, BS for a couple minutes and send me on my way.
 
#13 ·
I'm glad you have "friendlies" out there...in SoCal, I have actually recieved more citations from AQMD inspectrs than from the Law staff!

Anyway, I really like the Allieds on my vehicles...I (and my family) have used these on just about everything for 30+ years...although each vehicle I always try different mfgs to get the sound that I want and I really like the Allied resonators (glasspacks). They typically last 10+ years (they even outlasted the oem cats on the 97 Cougar), come in a variet of diameters and lengths (10" to 38" IIRR). They flow really as well as any perf muffler (including borla) and costs $20-$50 each. They have absolutely no drone, have a deep tone, nice rumble both on & off the throttle.
 
#16 ·
Its a federal law............so anyone (law enforcement or EPA officer) in any state can enforce at any time inlcuidng impounding the vehicle....that's another function of the Federal referee stations in every state...to evaluate any engine change that occurred in a vehicle that was not offered by the oem.
 
#17 ·
I ran 22 inch long 3 1/2 inch wide straight pipe exhaust tips for one summer (with and without resonator). The big tubes act as a huge sound chamber and the sound produced was a deep, complex, growl. My friends said it sounded like an angry Wookie. That summer my cats clogged and i replaced them with high flow cats and a newer moddel resonator (has a straight through design). It sounded like two Harley Davidsons riding side by side.

Exhaust tips are the final part that shapes your exhaust tone. People would be supprised how big of a difference it makes.

Exhaust Tips/Tubes
 
#20 ·
no law like that in michigan... only thing youll get a ticket for is no exhaust [open headers] cus its too loud and its disturbing the peace basically so they will pop you for that but its a write off ticket.. get exhaust put on and then show another officer and they can sign off on it and no ticket =]
 
#24 ·
since you did not want to do the search I went and did it for you.
Directly from EPA website.
WARNING: Federal law makes it illegal for ANYONE to tamper with, disconnect, remove or otherwise render inoperative ANY emissions-related control device. The Environmental Protection Agency and most states have actually been rather lax about enforcing this rule on motorists, but they haven't hesitated to nail professional service facilities that have been guilty of tampering. Even so, the fines can be hefty. A violation may make you liable for up to a $2,500 fine!
also
Revisions to the Clean Air Act in 1990 further broadened the definition of emissions tampering to include virtually ANY type of engine or exhaust system modification that alters what comes out the tailpipe. That means any nonstock aftermarket part that is installed on your engine must be EPA-approved and emissions legal (except on the exempt vehicles previously noted).

Before the law was revised in 1990, it was only illegal for professional mechanics to remove or disconnect emission control devices. There was nothing to prevent a motorist from tampering with their own vehicles. That loophole has since been plugged.
so If you do anything more than change your plugs or wires you could be fined up to $2500...not exactly $20,000 and/or a year in prison
Alan
 
#28 ·
There's a bunch of different reasons for a vehicle to be exempt. In PA if you drive less than 5k a year its exempt. Also if its registered antique or classic its exempt. You can also get a waiver if your car fails emissions. You just have to spend $200 on emissions related parts. So, if you cut your cats out and you spend 200 on plugs and wires or anything else that can be considered emissions related they slappe a waiver sticker on it and your good to go.
 
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