i recently had an experiance that can prove how back pressure is necessary. At the beginning of my 3 hour drive Sunday, my exhaust pipe cracked and split apart due to a lack of flex.




this created an "open header" exhaust that many 400hp+ domestics use. I have a DOHC B16b motor with an exhaust manifold measuring 2 1/2in in diameter so I clearly make more power than a 1.5L dx and have plenty of "flow". I have had this setup now for 5 months. My point is - when my exhaust pipe cracked and left me with an open header (no backpressure) i noticed an extreme loss of torque and low rpm horsepower. My 3 passengers who have never heard the word "back pressure" also noticed a dramatic loss of power. Without the back pressure provided by my Greddy SP exhaust, i was unable to make torque and unable to out accelerate minivans. I know my experience involves much more power and much less backpressure, but the rule stands. Civic 101: You're Japanese economy car needs backpressure.