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Discussion Starter #1
Well i was thinking, the mazda6 has the 2.3 with dual exhaust and the 3 has single with a shorter distance to travel. I assume the stock piping is 2" or so. I am gonna go with 3" pipe all the way, Should it still be just about the same flow area as the 6's exhaust? It should free up a few horses and my friends are having a dyno day shortly and i want to have it done to do some numbers.

EDIT: As always, topic heading for clarity :)

NOTE: Usually 3" is not enough :)
 

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3" for a 4cyl is a no no. It totally eliminates backpressure.... which is essential for low end torque.

Typically, 4cyl exhausts are below 2"... maybe 1-7/8". Max, and I mean max would be a 2.5" mandrel exhaust. Most exhaust companies make their exhaust 2-1/4" which seems to be best tuned for the 2.3l.
 

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Yeah you don't want to go to 3" unless you're planning on going Forced Induction I would think
 

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Discussion Starter #4
ahh see thats what i thought
i had a civic for a long time and 2.5 fo rit was pushing it.
 

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Do a Dyno before the mod then just after the mod and see if it makes a difference.
 

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Discussion Starter #6
D said:
Do a Dyno before the mod then just after the mod and see if it makes a difference.
yeah thats what i was gonna do cuz i get 3 runs for 40 bucks :D
i am gonna call in my order tomorrow and try to slowly break in my car before we dyno next month and then put on the exhaust at the shop after my 1st run. To bad they don't have a header out yet :(
 

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ya 3" is overkill for a NA 4-cyl... only 200+hp turbo 4's benefit from an exhaust that big!
i have a 55mm system on my Jetta and its perfect for the few engine mods done to the 1.8 8V...
 

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would 2.5" still be good if you do install a turbo? or should u make it 2 and 3/4" pipping?
 

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2.25" should be plenty big enough for a naturally aspirated 4 cylinder. You may gain a tiny bit of power going bigger, but mostly you gain a lot of loud.... The big restriction is at the header and the cat anyway.

As far as loosing horsepower by going too big in an exhaust, that is urban legend. In a header portion design you might have to wory about exhaust scavenging an velocity which might dictate the primaries size, but backpressure is a negative always. Unless you hate your ears 2.5" is max, and will probably be loud enough to wake the dead.
 

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funkyfreshmonke said:
would 2.5" still be good if you do install a turbo? or should u make it 2 and 3/4" pipping?
2.5" is a good streetable size for a turbo. But for maximum output a 3" would be better. Backpressure works for turbos too.. because full boost isnt usually till 3000 rpm. So the motor up till then would act like a N/A motor.
 

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Discussion Starter #12
i am thinking about ordering the exhaust fomr kenstyle when i order the kit from them
i like that tip they have on it.

thanks guys
 

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birdy said:
Well i was thinking, the mazda6 has the 2.3 with dual exhaust and the 3 has single with a shorter distance to travel. I assume the stock piping is 2" or so. I am gonna go with 3" pipe all the way, Should it still be just about the same flow area as the 6's exhaust?
The 6i is quasi-dual, not true dual.
 

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"The 6i is quasi-dual, not true dual."

BINGO

2.25" is good enough for most people. If you want more top end power on this 2.3L and you install a race header and more agressive cams at some point, going to 2.5" will get you more power. At least this is what we have found while testing this 2.3L engine.

Nikolas
 

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I personnely wouldn't go any larger than 2.25 inch for an exhaust on the 3. I made the mistake of going with a 2.5 inch diameter pipe along with a Dynomax Ultraflo muffler on my old 98 Dodge Neon R/T. Power seemed to increase between 5-7k, but low end torque/umph was greatly sacrificed. It was fine for racing but for around town it was a bitch.
 
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