Thread: custom exhaust

i plan to create my own exhaust with no cat, and i want to use 3 inch aluminum piping, i am not turbo out, i need to no if i am heading in the right way. Cuz i rather build my own exhaust cuz i know people how can bend the piping and weld it for me so its just need material and its free labor. I know i will need to weld back the three o2 sensors back on and adjust the spacing on them so the MIL light does not come on(hate that shite), so i need some advice on the size piping, muffler, and should i keep the cat, im going to gut the pre cat out and weld it back together so thats out of the picture. I was wondering if the exhaust vaule will burn up cuz of the new incress of air flow, or what will happen to the engine if i put this big of a pip on it.

Big pipes flow more, so is bigger better? Answer: absolutely not. Primary pipes that are too big defeat our quest for the all-important velocity-enhanced scavenging effect. Without knowledge to the contrary, the biggest fear is that the selected tube diameters could be too small, thereby constricting flow and dropping power. Sure, if they are way under what is needed, lack of flow will cause power to suffer. In practice though it is better, especially for a street-driven machine, to have pipes a little too small rather than a little too big. If the pipes are too large a fair chunk of torque can be lost without actually gaining much in the way of top-end power. is this true about our cars

stick with 2 1/2". 3 inch will be way to big for n/a. and why use aluminum piping. The only thing you'll be doing is restricting the flow since the piping will be crush bent. stick with stainless steal cuz it wll be mandrel Bent.

Get a header instead of gutting it. The inner diameter of the header runners are way better then stock.

Originally Posted by nightrider45

stick with 2 1/2". 3 inch will be way to big for n/a. and why use aluminum piping. The only thing you'll be doing is restricting the flow since the piping will be crush bent. stick with stainless steal cuz it wll be mandrel Bent.

Get a header instead of gutting it. The inner diameter of the header runners are way better then stock.

+1 and 3 02 sensors?

the thing is i rather just gut it out to save some money and drop it on the piping, but i really want some headers but the cost alot, i need to find a good used one and then ill be happy, but yea theirs two o2 sensors on the stock headers/precat and one by the cat.

u can find them on ebay for a 100 bucks or so, it's well worth the money.
and there should only be 2 o2 sensors

okay now im confused i though their was three o2 sensors i know one is before and one is after the precat, and i believe one is after the cat.

Originally Posted by shaun11423

okay now im confused i though their was three o2 sensors i know one is before and one is after the precat, and i believe one is after the cat.

theres only 1 by the precat and 1 by the lower cat

since u have an 02, you will see the 2 sensor from up top when u open the hood, u dont have anything under the car. only the 04-06 does

2 sensors.. stock positions are one on precat header and one on midpipe

not 3

second question. 3inch is too big. 2.25 is just slightly too small. run with 2.5.. i have nismo and i think the piping is somwhere between 2.25 and 2.5

3rd. XS POWER HEADER AND MIDPIPE = $210 plus o2 spacer so u dont throw codes. best money u will ever spend and its brand new shipped to your door

just an fyi for my opinion..no cats is fine, no resonator is bad. our cars sound just as bad as civics with no resonators.. im catless with the nismo resonator and muffler and i get complimented alot on the sound of it. sebbie (specbee) has the same setup and everyone loves how ours sound.

i have a header $50 2 o2 sensors btw

okay im going with the 2.5 and i though their was 3 but their 2 okay thats even better for me, now whats the deal with the spacer on the o2 sensors so they dont kick the light, do i need them or not.

im really not looking for headers at this point of time, ill check you latter when uncle sam hit me up.lol

im just guessing that the stock pipe is a inch 1/4?

Originally Posted by shaun11423

okay whats the deal with the spacer on the o2 sensors so they dont kick the light, do i need them or not.

look in the how to's there's a antifouler mod that u can do to keep the engine light from being on.

aight im going to tackle the pre cat tomorrow, ill keep you guys posted

the spacer helps reduce the chances of u throwing a code

its basically a thread extender

screws into the old thread and hole and moves the threading up about half inch

so i took out the heat shield top and bottom and it started to pour down and i closed up shop but i noticed on the headers right behind the alternator theirs a nut hiding their does anybody think i should move the alternator or i could mover the reserve coolant box to make space and squeeze in and dam those nuts are tight im afraid im going to strip it but wait gator grip is coming to save the day.

u have to take the alternator out to take the manifold off when u put the header in.

use a bolt out because you probably will strip them and yes move the alternator

i figured but why did Nissan design it like that, its really stupid, i was looking on some manuals from Nissan and they said to torque the bolts and put take them out and tighten them up in a pacific order.