Originally posted by Dave C
As a general rule 4-2-1 headers give a bit more torgue while 4-1 give more top end HP. Same applies to pipe size, smaller more torgue, larger more top end HP.
true, but...
headers are one of the first mods, but do it right. i wouldnt suggest dc, apex, mugen, or oem. save a little bit more money and get a custom header done, or look for an a&n pro header. there are 2 things a 4 cylinder header needs to make it worth money-no mandrel bends and telescoping collector. mandrel bends take away from the velocity of the exhaust, therefor you want a header with formed 90 d. elbows. read up, this was true 5 years ago in superbike racing. telscoping collector picks up torque as well, without sacrificing top end power. it picks up torque by increasing velocity. this has been proven effective in the enzo ferrari, a 250,000 dollar car.