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The Terminator
Exhaust
Does a 3" catback really make any difference over a 2.5"?
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<blockquote data-quote="ctgreddy" data-source="post: 14680171" data-attributes="member: 122280"><p>You're not going to gain more than 5whp with a 3inch over a good 2.5". Here's some comparisons from cars at my work which aren't cobra's and different power levels. </p><p></p><p>On a 2015 mustang, we put SW 1 3/4 primary/3" collector longtubes on, but that necked down to 2 1/4" stock size, then a 3" gibson which necked down to 2 1/4. That car with a jlt cai made 445whp. On another 2015 that got arh lt's with the same sizing but full 3", into a modified gibson catback so this one is full 3". With the same intake on the same dyno and in the same weather conditions it made 447whp. </p><p></p><p>Now on zl1's, they have a good free flowing catback from the factory. On our ooooold shop car we went from the factory 2.5" catback to a 3" corsa on a car that already made 700+whp. It made within 5whp of what it did before but it was a couple years after the initial pulls but on the same dyno. </p><p></p><p>Then you've got guys on here like Timspony who only picked up 2x whp by switching out stock ex manifolds to bassani midlengths and that was in the 7xx whp level. So how much of a restriction is a good 2.5" catback going to be if the ex manifolds aren't even a very big restriction?</p></blockquote><p></p>
[QUOTE="ctgreddy, post: 14680171, member: 122280"] You're not going to gain more than 5whp with a 3inch over a good 2.5". Here's some comparisons from cars at my work which aren't cobra's and different power levels. On a 2015 mustang, we put SW 1 3/4 primary/3" collector longtubes on, but that necked down to 2 1/4" stock size, then a 3" gibson which necked down to 2 1/4. That car with a jlt cai made 445whp. On another 2015 that got arh lt's with the same sizing but full 3", into a modified gibson catback so this one is full 3". With the same intake on the same dyno and in the same weather conditions it made 447whp. Now on zl1's, they have a good free flowing catback from the factory. On our ooooold shop car we went from the factory 2.5" catback to a 3" corsa on a car that already made 700+whp. It made within 5whp of what it did before but it was a couple years after the initial pulls but on the same dyno. Then you've got guys on here like Timspony who only picked up 2x whp by switching out stock ex manifolds to bassani midlengths and that was in the 7xx whp level. So how much of a restriction is a good 2.5" catback going to be if the ex manifolds aren't even a very big restriction? [/QUOTE]
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Does a 3" catback really make any difference over a 2.5"?
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