First of all, I know how a header works and the pros and cons of SRIs and CAIs.

I plan on looking around ebay for an OBX or Megan header and an SRI (because I live in Northeast Indiana and it can get pretty wet.)
My question is: where in the rpm range will performance increase? I've heard that installing a header will hurt low-end torque but boost performance on the high-end.

 

your right about the headers, but the cai helps more on the high end also. the exhaust helps the most with the low end. btw, if it is wet alot where you live, then you are gonna wanna get a bypass valve for your intake.

 

he getting a sri so he will not need a bpv

 

an exhaust if anything would help with high end, not low end. generally the piping size optimal for the amount of HP the motor makes is determined at higher rpms. variable piping diameter would be ideal, but that doesnt exist at this current time.

 

really? i remember people saying that exhaust was low end power when i was buying my exhaust, and cai was high end. so nothing really helps the low-end in an I/H/E set up. unless the cai does and i am getting the two mixed up.

 

wtf. i mean it helps a little. most hondas dont have much low end anyway. id say i have more than most..but i wish i had more. want more low end power and torque? get a TB spacer!!!!!!!! woohoo!

 

First, the TB spacer doesn't do anything but make a little noise.

I/H/E really doesn't help the low-end. Low-end torque is increased with airflow restrictions. This goes against the goals of the I/H/E setup. I/H/E will help the engine's airflow, improve high-end power and also allow the engine to rip through the lower rpms quicker to get to the power-band quicker. This last part is what makes you quicker even though your low-end torque has decreased from stock.

THIS IS WHY I ALWAYS TELL PEOPLE TO LEARN ABOUT THE TORQUE AND HP CURVE RATHER THAN THE PEAK!!!!

 

So whats really the deal with the headers? seeing that they have to bolt into the stock exhaust manifold position and then bolt onto the stock cat, how can it really increase performance, if its basically got the same diamiter? Is it just less restrictive? Similar to getting a hi flo cat? or is the matieral its made of what increases performance? Or is it the 4-2-1 design?

 

The gains from a street header are due to larger primary tubes and better smoother collectors. The area of a circle increases exponentially as compared to the radius, so a slightly larger primary can have a major effect on exhaust flowrate (A=pi*R^2). Also, the primaries can be tuned to match the engine thereby increasing power (usually long-tube track headers only). The better collector reduces parasitic backpressure caused by the cheaper stock design.

4-2-1 is better for low-end than 4-1, but the stock will still have better off-the-line torque. 4-1 will offer the most gains above 5000 rpms.

 

dude i was kidding about the spacer. i have one, but theres no proof either way if it works or not. therefore. when i get my dyno again hopefully sooner than later, im having a pull with it on, then with it off. from what they claim tthere should be some sort of difference. if it doesn do anything, im taking it off for good.