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Discussion Starter #1
Well I've read in 3-4 different threads on random postings that the aftermarket exhausts(Injen, Magnaflow, MS) don't really offer any horsepower/torque gains is that right? My question is if I were to unbolt my stock exhaust from the 2nd catback and buy another set of mufflers would i be shorting myself? I only ask as I plan to do custom exhaust in the long run with a 3" straight pipe and custom y-bend but for now i have to replace my TV so I can't drop that $ right now. So basically what i'm asking is if I buy a set of muffler tips and bolt em' on will I enjoy the sound i'd get or would this be waste? Keep in mind i do plan on doing the custom exhaust within 8-10 months.
 

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3" exhaust is not optimal for this engine. Generally you can take a realistic number that you think the engine will make with a free flowing exhaust and mutiply that number by 2.2 to find what cfm you need.
example: 235 est hp X 2.2 = 517 cfm. this is closest to a 2.5" pipe.

for reference (approx @ 10.5 in merc):
2": 360
2.25": 450
2.5": 560
2.75": 683
3": 810

these are straight, no restriction pipes. bends and anything else that obstructs airflow will reduce the numbers.
in theory, and I believe the cougar and contour guys have already proved this, this engine will make optimal power with either a single mandrel bent 2.5" exhaust with straight through mufflers like dynomax ultra flows or dual 2" with low restriction mufflers.

as a side note, the car won't see any worthwhile gains until you replace the exhaust near the manifolds. just have a look under your car and the mess mazda made of it. best (as someone I'm sure will chime in with) is getting headers and full exhaust. otherwise you're just making noise.
 

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Discussion Starter #3
yeah that's mostly what i figured is without headers it wouldn't make any real power difference. My other question is if i went with mufflers/tips what would you recommend?
 

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my personal preference for just an axle back (mufflers/tips) is the racing beat. it's supposed to be a real deep rumble that's not too loud until you're really on it. but it'll be a matter of your taste. listen to the sound clips ppl have posted. Check the cougar/contour forums for sound clips too, they sound similar since the motor is basically the same. Some people also like bigger tips. Doing a custom muffler/tip combo will be tricky since space is so limited on these cars. something I thought of doing was to replace the resonator with a 2.5" muffler turned sideways so it goes up into the tunnel under the car and then 2.5" back to a Y with no mufflers at the rear, just tips.
 

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Discussion Starter #5
i mainly want something that looks cleaner and sounds a big louder. not ricey loud but louder, i know the 6s can give off a nice sound with the right exhaust.
 

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for my turbo i'm doing 2.5" straight through, no cats, no resonator, which will y to two high flow turbo mufflers on the end. so i don't think anything above 2.5 is good on na
 

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Discussion Starter #7
i like the look of the injen the most and to get the muffler's for those it's 380 so i think i'll just go with that injen system eventually. easier install too.
 

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A catback exhaust should give you a 5-6hp increase over stock.

Magnaflow are probably the least expensive cat-back on the market. I really like the Mazdaspeed exhaust but it seems a little pricey.
 

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Discussion Starter #10
i am torn between the injen muffler/tips i've seen for 350 a pair and then just do custom piping if needed, or an injen SES system. anyone know the stock straight pipe size on the stock exhaust?
 

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it varies. at some places i measured as low as 2" and as much as 2.25". the rear section is about 1.75" inside diameter
 

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racing beat sounds good, but personally it looks ugly imo... its not big and bold like the magnaflow muffler or the injen..

save yer cash and get a magnaflow or injen. both only have great reviews. Remember yer gonna need kartboy hangers to.. but those only run you $32 shipped
 

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racing beat sounds good, but personally it looks ugly imo... its not big and bold like the magnaflow muffler or the injen..

RB is nice looking and not in your face ricey imo.....it's not big and ugly like magnaflow and injen. To each his own.
 

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Discussion Starter #15
my only thought/concern is if i can get the injen muffler and tips for 300-350 vs. the full exhaust for 680+ shipping, why not save the 300 bucks for the straight pipe?
 

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A catback exhaust should give you a 5-6hp increase over stock.

Magnaflow are probably the least expensive cat-back on the market. I really like the Mazdaspeed exhaust but it seems a little pricey.
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Cat backs do not give any gain over stock. Zero, zip, nada. Many dynos to back that fact up.
 
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