Rep Power: 0

Hey, so I have an 03 Civic DX sedan, auto. Everything stock (aside from the SRI). I already know the car isn't meant for power, I already know gains on an Auto are minimal, & especially minimal on a D17. I'm not here with the usual I/H/E questions asked over & over. I've read all the threads over different forums & I think I've learned to stay away from those mods in general.

The ONLY thing I'm looking for is a faster 0-60. & I don't mean TL acceleration times, I'm talking "get off my *** at the red light" kinda times. I know the DX has the cat built into the manifold, & I know I/H/E upgrades will only kill low end for more top end.

My car is automatic, & I very RARELY go over the 3000 rpm range, (3500 max). I've grown up on Civics, so I've got a feel for how to drive them smoothly, fast (well as fast as they'll let you), & as efficient as possible.

My question today, is if more velocity or back pressure (I always see different posts on which leads to more low end) equals more torque, if I were to upgrade to a shorty header (or maybe an EX header/manifold) with a high flow cat, but kept my stock exhaust, would that increase back pressure towards the cat-back or improve velocity? Could that give me maybe a little boost on the low end? Could upgrading the intake manifold with stock exhaust have a positive effect?

If it's a dumb question, take it easy on me. I'm new here & tried my best with the search button all over. The post was a last resort lol.

 
Rep Power: 367

not sure, most that change and exhaust only would not put car in a dyno...
and then there's the placebo effect to consider...

rev car everyonce in a while? that should clear some carbon deposits

the most effective way is usually milling the heads so you get small bump in compression ratio, but thats a lot of work...

 
Rep Power: 210

I doubt there is much you can do to increase torque signifcantly.

The scavenge effect people refer to is due to pressure waves reflecting from the valve, to a larger open area and then back. If this is timed correctly, it will improve engine volumetric efficiency. The smaller the primary tube the stronger this effect will be. As the pipe becomes too small, the steady state pressure drop (backpressure) across the tube will become large enough to negate the benefits of the "tune" provided.

If it were simply that backpressure increased torque you could partially block the tailpipe and see the effect. Headers are designed to that the size of the primary pipes and their length improves scavenging within a certain RPM range. I would be very surprised if you could find headers for a Civic that were designed for mid-range torque instead of high RPM horsepower.