Quote:
Originally Posted by XanderWiFi
After all the issues I have had with my headers and exhaust I finally take it to an exhaust shop that has a focus on custom exhaust set ups. As loud as Angel has been, I could have sworn there was another leak or something not welded/fastened properly.
Nope. Apparently it was all good. The only thing making it sound like I had no exhaust, was the size of my exhaust (2.5" pacesetter catback). It was also stuck against some things it was not supposed to be touching and put together in a crude fashion. They said they were going to move it around so it would not touch in places it should not, but instead they ran a new 2.25" piping to my pacesetter muffler/tips.
One of reddogs posts says the 2.5" is what works best for our cars. The shop owner says that 2.25" is more than enough for the HP the aleros have. The 2.25" is quieter but still sends enough flow to provide the rumbles I like from my pacesetter muffler. However, I can feel more back pressure from the gas and such.
Does the .25" make that much difference-other than the loudness I was not a fan of.
The pacesetter headers provide enough extra flow to turn the 2.5 into the loud monster from the muffler-rumble only with the stock headers.
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One important thing is the type of bends used. Mandrel bends are what you want, to maintain a constant radius and smooth flow at the bend. So 2.25 mandrel bent may even be better than 2.5 crush-bent. But 2.25 crush-bent is not acceptable with the headers.
As the exhaust gas flows toward the back of the car, it cools and its volume decreases, so it might be acceptable to start with 2.5 near the headers, but go to 2.25 further downstream. Transitions from large to small should be as gradual as possible, at least a 4 to 1 (of the pipe diameter difference) ratio is recommended.
Do not go from large to small then back to large in the transitions either, flow loss results in each change of radius. A possible exception to that is at the muffler itself or resonator if you use one. Easiest and probably best would have a constant radius throughout the system.
Usually, but not always, higher flow systems are louder.