Blow, inhale, hold, hold, hold... exhale, man! This time we speak about exhalation... I'm sorry, this time we speak about exhaust! As far as the windows of my bedroom face an avenue I hate RICERs who install cheap cat-backs and think that they are night razors! Hell no!
Never think that if you install cool cat-back your car will go faster and it will sound like a sexual V8. The only thing it will make - it will make your neighbors kill you one day. If you're going to tune the performance of your car you should take care of the whole exhaust system from the header up to the cat-back.
There are two different designs for a header. The 4-2-1 (or Tri-Y) and the 4-1.It is said that the 4-1 costs you low-end torque to give you more power up top. However some 4-1's have better low and mid then the 4-2-1 (you may find the info on the Net). Header designs on our Honda Civic stock D engines are so good that this is more a preference thing until you start building. One advantage of the two-piece 4-2-1 is that you can remove the lower half when you need to pull the oil pan, instead of pulling the entire header.
After the header the Catalytic converter comes. If your is still breathing you shouldn't care about it. For those of you who can afford to upgrade the cat, tests have shown that a 3" free flowing cat is close to the flow rate of a 3" test pipe. People have even made there own test pipes with minimal effort.
And now we come to the cat-back. If you own 1.6 L D-engine it's recomended you used 2.25" sized exhaust. However Spade says the best way is to use 2.5 inch: "My dyno results proved that it adds more power than the 2.25 and I gained another 1 whp throughout the power band when I removed the silencer from the muffler."
But, you also want to make sure you get mandrel bent piping and straight through designs on both the resonator (if you have one) and the muffler. If you don't get the straight through designs, you will loose power, it's that simple. However, with straight through designs also comes sound volume. A good compromise has is an exhaust that comes with a silencer. You can remove them for track days and leave them in for daily driving, as stated before, only losing about 1whp on a stock engine.
Dear readers don’t forget that these words are based on the experience from EG Civic. However you may use it as the general information. The main difference is the size of the exhaust and O2 sensor (there may be more than 2).
