Finally finished my downpipe

[Gannon]

I have had it on the back-burner for a while now, but i borrowed dads welder and did it last weekend.

This was my factory cat with a home-made bell-mouth from when i did my TF035 conversion.


If anyone has ever cut up the factory drinking straw that subaru put after the turbo, you will see why i replaced it.


So i bought another 2-1/4" mandrel bend, a length of pipe and a new high flow cat, and came up with this.

Looking down from the engine bay


From under the front


And from the side


I can feel a difference in power, not a great deal, but there is a difference, especially up towards 5000rpm.

Apologies for the poor picture quality, my phone doesnt adjust for afternoon sunlight very well.


The only other mod left to do now is neaten up the AFM to Turbo rubber intake pipe

[discopotato03]

Thanks for the pics Gannon , out of curiosity which Cat did you use ?
The reason I ask is because we will have to look for one in the near future and all I have lying around is a 3" Supercat .

My rally fabricator also wants to put the cat where you have but I'd rather leave that area for a resonator because there's not much space under an L Series to fit a second silencer .
So long as the down pipe is easy to remove I don't mind having a Cat in it , compact is good as long as it's free flowing .

I'd love to get my hands on an STi Rex rear muffler because they are supposed to be very quiet for their power output - 160 + Kw ?

How does you exhaust go from a noise perspective ?

Cheers A .

[Subafury]

nice work mate, looks well done

[Gannon]

The cat is just a 2-1/4" cat that i bought of an exhaust shop. Cost me $150

I have a 14" long hotdog about halfway along the car, and a straight through 2" oval muffler at the rear. The exhaust tip is just a piece of 2" stainless steel milk pipe. Looks stock and makes little noise. Still makes a noticable subaru burble though.

If you would like some more pics or even a sound file, just say

[discopotato03]

Say .

I don't want the "boxer burble" LOL .

It doesnt look like you fitted one on those spring loaded swivel joints behind the downpipe .

A .

[Gannon]

If you want to eliminate the boxer burble (which on my car is nothing like what 90% of wrx's with cannons slound like), you will have to make equal length headers. Thats the long and the short of it.

No i didnt fit a flexy joint. But i probably should have.

[discopotato03]

Really the only way to do that would be to make a divider plate and fit it through the siamesed exhaust port up to the heads divider between the exhaust ports . Then you would link the engine pipes between the front and rear pair of cylinders so that you get evenly timed exhaust pulses at the last collector .

The reason EA/EJ's burble and have that "off cadence beat" is because the cylinders in each bank (head) fire one after the other meaning two exhaust pulses followed by a time gap and then two pulses from the opposite head .
You don't get four evenly timed exhaust pulses like you do with an inline four cylinder with its exhaust manifold linking cylinders 1-4 and 2-3 , the firing order being 1342 means you get an exhaust pulse into each of the linked sides of these manifolds and even pulses at the last collector .

To be technically correct the ONLY Subaru flat fours that get the best from their four stroke cycles are the twin scroll turbocharged ones and if you look at their unique headers you can see why , they link the front and rear pairs of cylinders with roughly equal length header pipes to emulate what twin scroll in line fours have .

Sorry to be blunt but flat fours are nothing to do with technical exellence , they are just another way to package a four cylinder engine in the shells available space . It works but it's not all wins .

A .

[Gannon]

Just for shits n giggles i made some equal length headers (before my car was turbo) and it sounded like any other 4 cylinder

[discopotato03]

Hi Gannon , is it possible to see pics of the rest of your exhaust - and maybe the sound file ?

I have to do something with my exhaust and I want to start at the front and work backwards .

Now because I hate the trouble and expense of "transitional" parts I'll probably use the Lib RS dump pipe as a start because at least it should bolt up to the std RX's IHI turbocharger . I have no way of knowing what it's cat is like but I suppose I can at least use the pipe above the cat .

From memory early RS exhausts are around 57mm ID (?) so we can probably go 2.25 from there and possibly 2" at the back .

It needs to flow well enough to make low - mid range squirt and I'm not after high boost pressure .

Just concerned about the noise and don't want to sound like a back yard spares Rex racing team car .

Cheers A .

[Gannon]

I wouldnt bother with an RS downpipe cos
1. It wont fit the standard RX turbo
2. It cost me less than $200 to build my downpipe (including cat) using only a grinder and a gas-less mig.

My exhaust, which is 2.25" from the turbo to the axle, and then 2" from there to tip, with a hotdog halfway and a sports muffler at the rear, was way under legal sound requirements taken by an engineer.

[discopotato03]

Actually thinking about it your right , the flanges are different . I must have been thinking of putting the RX flange on the RS's bend .

I'll have to show the rally people the EA82T and RS Lib down pipes and see what they can put together - with a more modern cat .

I think the cat in the downpipe has a slight advantage in that the swivel joint can be as per std location (larger of course 2.25") and a resonator where the std one is and something possibly in 2" at the back .

In time , A .

[Gannon]

Thats something ive been meaning to put in mine, one of those flex joints.

And i should find a way of supporting it under the gearbox

[discopotato03]

My RX has a bracket bolted to the back of the gearbox and the swivel coupling is behind that .
I asked around the RS mobs site to see if anyone had the joint from an RS Turbo but no answers . I think the exhaust mobs can make them easily enough .

Actually does anyone have pics of the center section of an early Lib RS Turbos exhaust ?

Cheers A .

[Gannon]

Just a quick clip i took thisarvo.

Taking off in a 60 zone, crossing a bridge and turning left up a steep hill.
I tried to get a view of the boost gauge, but reflections killed it.

I can try again tomorrow, i'll even get Subarooster to hold my phone while i do a drive-by


http://www.youtube.com/

[subarooster]

i can definately vouch for this, the exhaust note from this combo is subtle but very nice. its a little louder and deeper than before but nowhere near as loud as the foresters and things you see getting around town just asking for attention from the boys in blue. haha we learned very quickly how loud it is when you take the muffler out and weld a piece of 2 1/2 inch pipe on... yes, it does sound like a 400hp sti but when you actually have 63kw's, people aren't impressed.

also, a hint of jelousy washes over me wen i see gannon gaining speed up that hill.... i have to change back to second.

cheers, Tom

[Matatak]

from what i can hear in that Video it sounds pretty decent.

ill wait for a drive-by one shall i

[Subafury]

boring- bring on the drive by! does sound nice tho the one bit i heard

[BlackMale]

Gannon what the hell man?!?! Hope you off roading what on earth is that clunk/grind noise about odd 20 seconds into the clip?!

[Ben]

That's terrible Gannon, we'll get some sweet subie action tomorrow though!

[Gannon]

Whats so terrible about it ben?

The noise at about 20sec is me crossing a timber bridge.