Exhaust System correctly set up

[SIMO888]

Good evening all,


After hrs. of research and quite a few phone calls I've come up with 2 style's for exhaust systems both will be to a person discursion. both are 2.5 up front end

there are a 2 options for upgrading headers, but first you need to figure out what you want first out of your exhaust. do you want pure power upgrades? or that classic Subaru "rumble"?


System 1

First and most important Manifold spacer

You want to start with this Phenolic Manifold Spacer
Grimm speed make these and work by lifting the manifold from the hot engine block. The material they are created from works as an insulation/heat soak between the block and the manifold. The cooler the manifold, the more dense the air and the more efficient the engine will run. This has been proven

EL heads let the exhaust pulses push and pull on each other as they meet in the piping as they exit the cylinders. Now this matched piping will result with that slight increase over UEL, BUT some will complain about any loss in that "rumble" that comes as a signature sound from most Subaru's make sure this is 2.5"

High flow Cat pipe:

Again freeing up some of the bottlenecks will free up them ponies. The catalytic converters aren't in place for power adding. Purely for emissions. The catalytic converter is in shortest explanation an exhaust air filter. It hold a catalyst that reacts with the exhaust gasses cleaning up at least some of the icky-ucky coming down the pipes

Cat pipe:
The cat is believed to be the highest restrictive part of the exhaust. most Subaru's have 2 cats which to me is a bit over kill. In saying this you can remove them but you will be playing with emission's and this will be deemed illegal and no recommended you do this unless its a straight track car

Mid pipe:
The Stock mid pipe has 2 resonators in it which quiet the tone of the exhaust. The major upgrade to these is increasing the diameter of the piping to match the rest of the exhaust to create better flow. A resonator/hotdog in these will help cut out any rasp or high pitch ping that goes through the exhaust, so they are highly recommended 2.25" pipe size nothing bigger or you will lose back pressure

Axle back and Piping size

still continue with the 2.2.5 piping size over all from after the 1st resonator/hotdog Piping diameter. This is really the key part on exhaust choice for our cars. Since we are NOT turbo'd we don't need a 3" exhaust. 2.25" diameter is proven to produce the best results. when you upgrade to 2.5 you start losing some of your low end power


so system number one 2.5 up the front end till you hit the resonator then drop to a 2.25" exhaust system



System number 2 the only difference is the headers so

this is where we all love the boxer rumble you will get some gain with the UEL header but not as much as an EL header system. and then as mentioned continuing 2.5 up the front end till you his the resonator then drop to a 2.25" exhaust system so you continue the back pressure which is very important in an N/A car don't let anyone tell you different cause they are lying and you will lose power guaranteed


EL vs UEL:

Properly let the exhaust pulses push and pull on each other as they meet in the piping as they exit the cylinders. Now this matched piping will result with that slight increase over UEL, BUT some will complain about any loss in that "rumble" that comes as a signature sound from most Subaru's. It's up to you do choose that one. The sound comes from the gap in the ignition pulses setting off the combustion in each of the cylinders. The factory exhaust exadurates that gap and some love that rumble to NO END!!! Key to note.


Back Pressure :


Keeping that backpressure talked about in the headers section is still important even way back here on the piping. Yes that means even just changing the axle back section of the exhaust or JUST the muffler can make an improvement. This is probably the most enjoyable first upgrade on any car let alone the NA's. Noted improvements can be noted on some NA cars as much as 10-15 ft/lbs of torque across the power band and 20 at peak when combined with just an basic intake upgrade.
Most will come as a two piece combo of a mid pipe connecting the catalytic section to the section connecting at the rear axles.

Over all it comes down to you as I said before if you want power or the classic rumble

I hope this has been helpful to everyone and please let me hear your feedback