Bull Run
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I recently completed my stealthy turbo back exhaust upgrade, which was done in phases.
Phase 1, 3" Corsa catted downpipe:
I chose the catted version to avoid stinky exhaust and for noise control. It still triggered intermittent CEL for rear O2 sensor, which was taken care with via tune. Other option is to use O2 sensor spacers.
Another reason I chose Corsa was that it came with end pieces that allowed me to mate it to the 2.25" inlet pipe of the stock resonator, with an option to upgrade to 3" piping later. I put the header wrap on the upper portion of the DP to reduce the under hood temperature. You can see in the picture below how the stock DP narrows down to 2.25" inch after the flex joint.
Phase 2, Borla Pro XS muffler, 3" inlet, dual 2.25" outlets:
Next step was to get rid of the next restriction in the exhaust flow, which was the resonator due to this 2.25" inlet. I chose Borla Pro XS muffler as it is basically a Y-pipe in a muffler. I stuck with dual 2.25" outlets as surface area of two 2.25" circles are greater than a single 3" circle. With stock mufflers in place, this setup sounded almost stock. I ran this setup for almost year.
Phase 3, GT stock mufflers:
I was content with my setup until I saw a post by [MENTION=11292]PewterCam[/MENTION] showing insides of a stock EB muffler. I never realized how restrictive stock mufflers were until I saw these pictures. Exhaust gases are forced to go through a restrictive screen first, followed by entering the inner piping that is less than 2" in diameter, before doing a 360 turn through that piping in order to exit the muffler.
While there are several great sounding axle back mufflers, they all come with noticeable increases in noise. I decided to look into stock GT mufflers as they can be picked up cheaply or even free from folks who upgraded their exhaust. If GT mufflers are good enough for 435-460 HP Coyotes, I figured they are good enough for stock internal EBs.
I found a picture of an opened up GT muffler and saw that it seems much less restrictive:
Added bonus is that rolled tips on GT (bottom) mufflers look better than EB ones (top) in a subtle way.
Driving impression:
It might be just in my mind, but throttle response seems to be noticeably better with GT mufflers over EB ones. Perhaps bigger turbo flows enough exhaust for EB mufflers to become a choke point.
As for the sound, I hardly noticed any sound increase unless I was in a parking garage with windows rolled down. I'm thinking Ford should've made it easy and used GT mufflers for EBs as well, but perhaps they went out of their way to strict EBs as much as possible.
So there you have it; if you're going for a sleeper effect, catted DP, Borla Pro XS, and GT mufflers will do the trick. If you like loud exhausts, this is definitely not the way to go.
Phase 1, 3" Corsa catted downpipe:
I chose the catted version to avoid stinky exhaust and for noise control. It still triggered intermittent CEL for rear O2 sensor, which was taken care with via tune. Other option is to use O2 sensor spacers.
Another reason I chose Corsa was that it came with end pieces that allowed me to mate it to the 2.25" inlet pipe of the stock resonator, with an option to upgrade to 3" piping later. I put the header wrap on the upper portion of the DP to reduce the under hood temperature. You can see in the picture below how the stock DP narrows down to 2.25" inch after the flex joint.
Phase 2, Borla Pro XS muffler, 3" inlet, dual 2.25" outlets:
Next step was to get rid of the next restriction in the exhaust flow, which was the resonator due to this 2.25" inlet. I chose Borla Pro XS muffler as it is basically a Y-pipe in a muffler. I stuck with dual 2.25" outlets as surface area of two 2.25" circles are greater than a single 3" circle. With stock mufflers in place, this setup sounded almost stock. I ran this setup for almost year.
Phase 3, GT stock mufflers:
I was content with my setup until I saw a post by [MENTION=11292]PewterCam[/MENTION] showing insides of a stock EB muffler. I never realized how restrictive stock mufflers were until I saw these pictures. Exhaust gases are forced to go through a restrictive screen first, followed by entering the inner piping that is less than 2" in diameter, before doing a 360 turn through that piping in order to exit the muffler.
While there are several great sounding axle back mufflers, they all come with noticeable increases in noise. I decided to look into stock GT mufflers as they can be picked up cheaply or even free from folks who upgraded their exhaust. If GT mufflers are good enough for 435-460 HP Coyotes, I figured they are good enough for stock internal EBs.
I found a picture of an opened up GT muffler and saw that it seems much less restrictive:
Added bonus is that rolled tips on GT (bottom) mufflers look better than EB ones (top) in a subtle way.
Driving impression:
It might be just in my mind, but throttle response seems to be noticeably better with GT mufflers over EB ones. Perhaps bigger turbo flows enough exhaust for EB mufflers to become a choke point.
As for the sound, I hardly noticed any sound increase unless I was in a parking garage with windows rolled down. I'm thinking Ford should've made it easy and used GT mufflers for EBs as well, but perhaps they went out of their way to strict EBs as much as possible.
So there you have it; if you're going for a sleeper effect, catted DP, Borla Pro XS, and GT mufflers will do the trick. If you like loud exhausts, this is definitely not the way to go.
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