thisaznboi88

iTrader: (7)

Will be showing exhaust gasket on head later.

Cliff notes:

Why do j-pipe and exhaust when your still limited by how much exhaust you can flow by the pre-cat. Stock pre-cat outlet is only 1.75in. Most j-pipe have a 2.25-2.5 inlet. So your limiting your flow. Most cat backs are 2.5in and I know some people are running custom 3in. So start with the PCD/HFPC and work your way down. To J-pipe and then exhaust. just my .02 cent

RV6 HFPC v3
outlet 2.14in


inlet 1.73in x 3.20in


updated with measurement of stock precat

Stock outlet 1.76in


inlet 1.47in x 3in




you can see with the gasket on that the precat tapers and gets narrower the more you go in. This blocks air flow






HFPC with gasket


HFPC weights 5 lbs


stock with heat shield is about 9lbs.


My o2 sensor after 110k

vietkid_2006

iTrader: (1)

That's pretty good logic with some facts behind it, I'll surely do PCDs before everything else now.

I hate cars

I agree about the order since you will probably get a better bang for the buck with PCDs. However, exhaust flow is the sum of all restrictions so even freeing up a smaller restriction will give you gains or us turbo people would be screwed LOL.

thisaznboi88

iTrader: (7)

if you have a turbo/SC you definitely need a PDC cuz your cat will last 2 mins :p

DC2many

This is true but not always the easiest or viable means to do

i.e.) Time+cost to install if on your own.
Time,cost, and labor if someone else has to do it.
Smog is a problem, unlike regular cats that are easy to re-install
Unless someone can say for sure they passed smog with high-flow or no cats at all

I've read it can take a minimum of 5 hours to do both precats

thisaznboi88

iTrader: (7)

the rear is the one that takes forever.. Since you have to take off the tower bar, and play tetris. If you don't live in a state that does emission it is well worth the time and effort.

took me about 1:30 to do the front with hand tools. The rear I will tell you how it goes next week. lol

EvilVirus

iTrader: (8)

^ I want to see your build when its done

thisaznboi88

iTrader: (7)

Don't worry. Going to try to get the car dyno tuned first so I can have a baseline before the head and camshaft gets put on