i read from somewhere that for N/A cars, it's better to have the exhaust piping long. for example, making loops here and there before exiting the bumper hole.
Is this true? i'm planning to use stock midpipe, convert to 3" piping, go around the rear diff and exit to the passenger side bumper hole.
i have a 3" custom y-pipe back exhaust with a resonator which sits low on the ground, and loud for me.
please enlighten me with how the exhaust back pressure works..

 

The thing you want to control is back pressure. In a NA (normally aspirated, non-forced induction) motor, the amount of back pressure can be used to control the torque "hump", as it were. Less back pressure moves the hump higher in the RPM band, more moves it down the band etc.

In a FI car, the less BP the better. Lower BP will get you the same HP with less manifold pressure.

As for "longer exhaust", no, you shouldn't add "curves" to the exhaust, each curve adds more restriction. What you may be thinking of is "long tube" headers. They are very good at getting that last bit of HP out of a NA motor. The only problem with them is you lose your CATs.

Even with the stock mid pipe, without a rear muffler, it will still be loud and raspy.

 

i've been driving around with only stock cats. crazy loud, and won't give good torque.
now i put back my 3" custom single, it's so quiet lol.
Would the loudness of only cats be same as, cats+stock y pipe+ bottleneck resonator+ 3" piping all the way out?
my end muffler interferes with rear bumper so i'll have to cut that muffler off (which is what i was gonna do any ways.)

 

loops??!?! can't tell if srs or troll..

 

recently, aftermarket exhaust came out for GTR(?) which costs nearly 10K. It got some serious loops(?), well extra piping where not necessary i guess.

 

It might be done to help accommodate mufflers in a tight space, like the rear of a GTR.

 

which exhaust? if you mean something like amuse that isn't performance based really. and some exhaust components have different components such as ART test pipes that help sound/performance, but they aren't loops

 

You don't have to sacrifice cats for long tube headers, you can run the XYZ pipe with the HFC attachment and then run whatever combo of midpipe and axleback