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-   -   Exhaust Piping Size (http://www.focusfanatics.com/forum/showthread.php?t=308798)

ripto 02-09-2013 08:26 PM

Exhaust Piping Size
 
From what I've gathered, the stock exhaust piping is 2". I'm trying to figure out what size I should get when I decide to upgrade, which will hopefully be soon. I'm looking at a Magnaflow catback system, but I see people with 2", 2.25", and 2.5" mainly. Are there any performance differences between them?

Roadworthy 02-15-2013 04:39 PM

The size of the pipe will give you very different results. On smaller displacement engines, having smaller tubes will help with low rpm torque (which small engines tend to lack) due to the the speed at which the exhaust will travel. Give that same small tubing at high rpm and you will create a bottleneck as the exhaust cannot evacuate fast enough.

If all else stock, just the exhaust piping diameter changing:
2" (stock) good low end torque but alright upper end power
2.25" (Magnaflow etc) low end torque drops ever so slightly but gain much more in mid and upper rpm power range
2.5" (other) low end torque hurts a bit but expect even better upper rpm power.

From what I've read, larger diameter exhaust piping will move your power band up.
Read up on Exhaust Gas Velocity and disregard the what people babble on about engines needing backpressure.

In all cases you will net a bit more HP and TQ, just don't think having a 3" on this N/A engine will give you the best high rpm power lol

ripto 02-15-2013 06:00 PM

Thanks for the info. What would you say are the RPM values separating low, mid, and high?

LOADED 02-16-2013 12:03 AM

2.25'' will be ideal If you don't plan on going Forced induction or moderate to high engine work Ex: Heads or cams.

ripto 02-16-2013 12:07 AM

Good to know. I don't plan on doing those type of mods, sounds like 2.25" will be my sweet spot.

ToreadorFocus 02-16-2013 12:08 AM

i personally have chosen the fswerks 2.5" race

FocusBoy58 02-16-2013 12:32 PM

Duratecs make the best power on 2.5" to 3" Maximum exhaust size. I went from 2.5" to 3" header back and bumped me up from 176 to 183whp, tq only increased very slightly but the torque was still a table top 140-157wtq from 2500 and up.

If you are going to spend the money get a 2.5" system period. trust me.

_RED_ 02-16-2013 03:50 PM

I agree with focusboy, and check the dyno thread to see numbers. Myself I am running a 2.5 and noticed no low end TQ loss if anything I gain some low end tq

Creative 02-16-2013 05:58 PM

2.5 is by far the best from my point of view. The fswerks feels great.

Bwill9886 02-17-2013 03:55 PM

I certainly felt no torque loss on my 2.5" exhaust.

To me it sounded like companies that chose to go with 2.25" exhausts were doing so for better sound quality (at least in their opinion) and sound level.


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