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Thread: Another Dual Exhaust Post... Reply to Thread
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Topic Review (Newest First)
07-25-2012 05:10 PM
Dink7898
Quote:
Originally Posted by 2012Tuxedo View Post
I had though about doing this with a comaro/firebird 80 series Flowmaster, but with larger 3.5" black tips (dont judge me, my F150 has 5in tips)

Which muffler is this and how does is sound on the 4? Im looking for deep, I want to go with a 2.5" catback exhaust with a compast hich flow cat behind an FS werks header.
I was looking into something similar. My plan would be race header, FSwerks stealth, with lunchbox that has dual output. I'm not sure how much it would quite the stealth exhaust with an extra muffler added in.
07-25-2012 04:44 PM
2012Tuxedo
Quote:
Originally Posted by rick47 View Post
I do like you on mine, it's a dual Camaro muffler ... sound loader, just ok
I had though about doing this with a comaro/firebird 80 series Flowmaster, but with larger 3.5" black tips (dont judge me, my F150 has 5in tips)

Which muffler is this and how does is sound on the 4? Im looking for deep, I want to go with a 2.5" catback exhaust with a compast hich flow cat behind an FS werks header.
07-14-2012 11:32 AM
dyn085
Quote:
Originally Posted by Brabs_Weather View Post
This decrease in velocity will slow the gasses from exiting the exhaust , which should cause pressure to increase slightly.
This is also true, which is good for torque. Notice the difference between Red and Focusboys dyno charts. While there are many contributing factors, the header makes a huge difference in the torque curve. Or, in Focusboy's case the lack thereof. His table-top torque curve should represent an increased driveability.
07-14-2012 10:59 AM
Brabs_Weather
Quote:
Originally Posted by dyn085 View Post
Bernoulli's Priciple will give you some insight. An engine is just an oversized air pump...it's not that there's more air flow, just that the velocity changes. Temperature, pressure, and velocity go hand in hand. Your header was smaller piping and was high temp, so velocity was high. In the 2.5", it had more room and time to cool, so velocity slowed. You can only flow out the same amount that flows in.

There's so much more to it, but thats a quick overview.
This decrease in velocity will slow the gasses from exiting the exhaust , which should cause pressure to increase slightly.
07-13-2012 10:32 PM
Dink7898 Interesting. I never got that deep into building my last Focus. I knew where I wanted my powerband and added components based where they improved that area. I eventually wound up with a car that had incredible top end because of the mix and match that I did. And by incredible I mean vs. how it was stock.
07-13-2012 06:45 PM
dyn085 Bernoulli's Priciple will give you some insight. An engine is just an oversized air pump...it's not that there's more air flow, just that the velocity changes. Temperature, pressure, and velocity go hand in hand. Your header was smaller piping and was high temp, so velocity was high. In the 2.5", it had more room and time to cool, so velocity slowed. You can only flow out the same amount that flows in.

There's so much more to it, but thats a quick overview.
07-13-2012 06:07 PM
Dink7898
Quote:
Originally Posted by dyn085 View Post
For the most part, you are pretty much correct to a degree. There is a size over stock, even while maintaining the stock header and cat, that gains will be seen. Ours is roughly 2.5" (from members testing). Above that you lose drive-ability, while below that you don't get max performance.

And anyone changing a tip with the thought of gaining performance is sadly mistaken. Strictly a sound mod. I even did a dyno run to show this with our lunchbox delete. The only performance gain you see is the loss of the weight.
So why does that happen? How does more air flow past the restriction than would normally be allowed because of a larger ID exhaust. I'm not doubting you just curious. And to think the whole time I owned my 01 with my shorty header that was the one thing that I always thought was mismatched (header - 2.25, hi-flow cat - 2.50, borla - 2.50). Not that it would have made any difference. Maybe like .5hp but it bothered my OCD. I dont think I could have squeezed any more power from my 01 without an SCT tune.
07-13-2012 05:41 PM
dyn085
Quote:
Originally Posted by Dink7898 View Post
I would think that performance would be more determined by ID of the exhaust and restrictors more than what tips are installed. You could put a 6in exhaust starting at the cat going to the back of the car but your not going to get any more performance than whatever the smallest ID of the entire exhaust would be depending on the restrictions. So if you have a header with a 2in exit you might as well have a 2in exhaust from the front to the back. At least that is how I have always thought how it worked. You see people driving Civics all over this area 6in tip out the back but a stock pipe going into the muffler. There is no way the provides any kind of increase in power. I can see dual tips changing the sound more than it would effect performance. But I dont have alot of experience with exhausts other than the Borla 2.5in I had on my 01. My shorty header collector was only 2.25in if I remember correctly. On second thought I have no idea what I'm talking about.


For the most part, you are pretty much correct to a degree. There is a size over stock, even while maintaining the stock header and cat, that gains will be seen. Ours is roughly 2.5" (from members testing). Above that you lose drive-ability, while below that you don't get max performance.

And anyone changing a tip with the thought of gaining performance is sadly mistaken. Strictly a sound mod. I even did a dyno run to show this with our lunchbox delete. The only performance gain you see is the loss of the weight.
07-13-2012 05:18 PM
FocusOnMeNow Thanks for the tip.
07-13-2012 11:26 AM
Dink7898 I would think that performance would be more determined by ID of the exhaust and restrictors more than what tips are installed. You could put a 6in exhaust starting at the cat going to the back of the car but your not going to get any more performance than whatever the smallest ID of the entire exhaust would be depending on the restrictions. So if you have a header with a 2in exit you might as well have a 2in exhaust from the front to the back. At least that is how I have always thought how it worked. You see people driving Civics all over this area 6in tip out the back but a stock pipe going into the muffler. There is no way the provides any kind of increase in power. I can see dual tips changing the sound more than it would effect performance. But I dont have alot of experience with exhausts other than the Borla 2.5in I had on my 01. My shorty header collector was only 2.25in if I remember correctly. On second thought I have no idea what I'm talking about.
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