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Originally Posted by Idaho Red Rocket 3
Hello Harryrcb,
What happened ?
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Sorry about not getting back to you. putting the secondary cats back did NOTHING. so after some thinking about what's going on and remeasuring everything, I realized the headers were 2" pipe at the flange and the mid pipes were 1 3/4" so I made new pipes with 2" dia and replaced the 1 3/4 " catless mid pipes. I was thrilled, got all my low end power back , increased my mid range torque considerably which showed up at the track went from 2:38 to 2:33 at Sebring. The muffler inlet pipes are still at 1 3/4" so I'm wondering what would happen if I replace those with 2" . This will be a little more difficult unless I make up a whole new muffler system.
The back pressure theory is not incorrect, I know if you go with too large a diameter pipe you loose all back pressure and lots of power, but these stock pipes are far from too large. I know some race guy who use 2 1/2" exhaust pipes with no muffler and gain hp and torque.
Around christmas time I put my stock s muffler back on because the Borla is realy loud and I went to visit my mother so I wanted it toned down, well the extra back pressure definitely reduce the power and it sounded strange, more like stock although throatier but not good.
anyway I'm working on another project now since I daubt I can get anymore hp and torque out of this engine. It was at 310 up from 256 before the pipe change but have not had a chance to run it on the dyno. This engine might be for sale soon if interested pm me.