legacy guys with exhausts, help

[Flex030]

Flex030, u think it wud be better to do the entire turbo back by farley or go aftermarket catback and let farley do the downpipe alone?

Well I think it's a matter of choice and your pocket size I.M.O.
Your entire exhaust system is very important hands down but if I had to compare a turbo back or catback to a DP I would say your DP is just as or even more important. (I prefer a turbo back than a catback btw).

You see the most important thing with a down pipe is to minimize turbulence as much as possible at the turbo outlet when the waste gate opens; same goes for any exhaust system. In some aftermarket DP brands you would see a bell mouth, bell mouth with a splitter plate or two separate pipes. (Stock Legacy is a 2 ½â€

[Bacon]

Get on Flex030

[Conrad]

Basically the rest of your exhaust i.e. mid pipe, turbo back, barrels should be as straight as possible with minimum bends/kinks and a free flow barrel as to reduce turbulence hence resulting in a free flow; not too free though there must be some resistance present.

I don't think this is true.

In ALL exhausts you want to maximise the velocity of the exhaust gases.

In a turbo application there is already a "restriction" caused by the turbo unit itself. You simply want to have as little turbulence as possible, that's where the down pipe comes in, it's best to have a dp with smoothe transitional bends but not always this is possible due to the engine bay dimension and turbo location.

The first 2-3 ft. of exhaust after the turbo is most important to maintain that velocity that I first described, after that the bigger is usually better rule applies i.e. cat-back.


Anyone feel free to correct me if I'm wrong because I'm here to learn too.

[Alpha_2nr]

^Correct...but just to expand on your point....

...in an N/A car, you want to maximise exhaust scavenging (hence the limitation in pipe diameter depending on cc of the engine).

...in an F/I car, you want to encourage high volumetric flow of gases through the turbine, so technically, a bigger diameter cannot really hurt (up until the point were you start to get cylinder "blowthru" of combustion gases).

[Flex030]

^^^^ Ok guys fair enough thanks...

BUT!!!!!

I was just looking at it from the point of view where a STi owner had a 4" system on his car and he lost a vast amount of power not until he went back to a 3" system he re-gained some power.

From this stand point I made that statement maybe I should of been more specific when I said that ...

[Conrad]

Man, we're all learning. Some people forget that on 2NR.

BTW, was it 4" from the turbo-back or was it from cat-back?

[jadakiss]

Thanks Flex030, pretty detailed answer there

I see CB posted a link to a catback tho...so if i were to get sumthing like that, plus an after market downpipe and take it to Farley,would that be a good option ? The price of the XO2 Catback is pretty good...how would Farley's price for a catback compare with that?

Im also concerned about buying an AM DP and it not fitting properly...i tink i heard copper having some issues like that....thats why i was leaning towards a Farley DP instead...but i wud have really liked an AM one

[Flex030]

Conrad, I'm not sure buddy I just saw the exhaust pieces on the ground, I did not ask the guy but I assume it was the entire exhaust from what I saw on the floor minus the DP. It looked real huge and funny.

Hence the reason stated why he told me he was changing it to 3"

[Flex030]

Thanks Flex030, pretty detailed answer there

I see CB posted a link to a catback tho...so if i were to get sumthing like that, plus an after market downpipe and take it to Farley,would that be a good option ? The price of the XO2 Catback is pretty good...how would Farley's price for a catback compare with that?

Im also concerned about buying an AM DP and it not fitting properly...i tink i heard copper having some issues like that....thats why i was leaning towards a Farley DP instead...but i wud have really liked an AM one

No probs buddy, being enthusiastic to share info is always an excellent learning practice for everyone.

Price you have to discuss that with him, compare and do the math.

The DP (USA) is not a prob you could have it removed and a JDM plate tig welded no biggy...

[Ragnarok]

^^^Or i could bring in a nice zerosports or hks downpipe for you....

[copper_shot]

Im also concerned about buying an AM DP and it not fitting properly...i tink i heard copper having some issues like that....thats why i was leaning towards a Farley DP instead...but i wud have really liked an AM one

the US Downpipe is not the same as the downpipe for the JDM legacy

well its the same bolt up, but the flange that bolts onto the turbo is different

so basically you need to cut off your flange from your stock downpipe and cut out the flange that came with the US downpipe and weld it
everything else bolts on.

---------------

aside from that

i heard the farley exhaust, i'm sure it performs great
excellent build and quality of work, if i wasnt told i would have thinked its an HKS or some other good brand.

but... it was too noisy for me

in the end, i decided to stick with this
invidia 3" Catless Downpipe & removed the other catalyst \
on idle sounds like stock, on high RPMs its roars a little louder ( a good little that is)
and it peforms great!

after hearing a couple legacys with aftermarket barrels i decided to stick with the stock barrels, i cant take that noise everyday (daily driven), if i ever decide to change them i'd definitely go with the HKS Silent Power, thats the best sounding IMO

[jadakiss]

^^^ i totally agree with you..i love the farley exhaust's but the sound draws too much attention. I'm still goin for that sleeper look (and sound lol)

I don't mind alil roar at WOT but im sure as hell keping my stock barrels like u did copper_shot,. I drive almost 1hr to work at mornings and i'd be hard pressed to say i want to hear all that noise for start to end...

Thanks again for the info guys Ragnarok, i will do some research on the types u stated above..

[copper_shot]

now.. if you're bored...

you can go with the hogzaust lol

simply add a couple washers to leave a gap between the pipe and the barrel

to give you that "aftermarket exhaust sound"

lol good thing about this, after a couple drives and you're fedup of the sound you can go back to your stock sound.
its a good thing to try if you're thinkin about going with an aftermarket exhaust to see if you can live with the sound.

btw, doesnt sound like an exhaust leak

try it this weekend if your bored, a 15 mins install

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[RB25-DET]

Nice one coppers!!!!

[Flex030]

Yeah coppers good one....

But i doh like the sound for a leggy IMO.

[nemesis]

Zerosports downpipe HKS Hi-Power Silents!

[Ragnarok]

^^^^Have the HKS silent power already,shipping in the HKS downpipe....

[copper_shot]

Zerosports downpipe HKS Hi-Power Silents!

\

i typed this before and didnt post it

but of all the exhausts i heard on the leggys
the HKS silent power are the best sounding, very quiet and nice tone

[Conrad]

An excerpt I have always kept at hand that may be applicable to what you guys are looking at.



The following excerpts are from Jay Kavanaugh, a turbocharger development engineer for Garrett Engine Boosting Systems, responding to a thread on Impreza.net, regarding exhaust design and exhaust theory:

“Howdy,

This thread was brought to my attention by a friend of mine in hopes of shedding some light on the issue of exhaust size selection for turbocharged vehicles. Most of the facts have been covered already. FWIW I'm an turbocharger development engineer for Garrett Engine Boosting Systems.

N/A cars: As most of you know, the design of turbo exhaust systems runs counter to exhaust design for n/a vehicles. N/A cars utilize exhaust velocity (not backpressure) in the collector to aid in scavenging other cylinders during the blowdown process. It just so happens that to get the appropriate velocity, you have to squeeze down the diameter of the discharge of the collector (aka the exhaust), which also induces backpressure. The backpressure is an undesirable byproduct of the desire to have a certain degree of exhaust velocity. Go too big, and you lose velocity and its associated beneficial scavenging effect. Too small and the backpressure skyrockets, more than offsetting any gain made by scavenging. There is a happy medium here.

For turbo cars, you throw all that out the window. You want the exhaust velocity to be high upstream of the turbine (i.e. in the header). You'll notice that primaries of turbo headers are smaller diameter than those of an n/a car of two-thirds the horsepower. The idea is to get the exhaust velocity up quickly, to get the turbo spooling as early as possible. Here, getting the boost up early is a much more effective way to torque than playing with tuned primary lengths and scavenging. The scavenging effects are small compared to what you'd get if you just got boost sooner instead. You have a turbo; you want boost. Just don't go so small on the header's primary diameter that you choke off the high end.

Downstream of the turbine (aka the turboback exhaust), you want the least backpressure possible. No ifs, ands, or buts. Stick a Hoover on the tailpipe if you can. The general rule of "larger is better" (to the point of diminishing returns) of turboback exhausts is valid. Here, the idea is to minimize the pressure downstream of the turbine in order to make the most effective use of the pressure that is being generated upstream of the turbine. Remember, a turbine operates via a pressure ratio. For a given turbine inlet pressure, you will get the highest pressure ratio across the turbine when you have the lowest possible discharge pressure. This means the turbine is able to do the most amount of work possible (i.e. drive the compressor and make boost) with the available inlet pressure.

Again, less pressure downstream of the turbine is goodness. This approach minimizes the time-to-boost (maximizes boost response) and will improve engine VE throughout the rev range.

As for 2.5" vs. 3.0", the "best" turboback exhaust depends on the amount of flow, or horsepower. At 250 hp, 2.5" is fine. Going to 3" at this power level won't get you much, if anything, other than a louder exhaust note. 300 hp and you're definitely suboptimal with 2.5". For 400-450 hp, even 3" is on the small side.â€

[BZ]

Now all questions and concerns have been addressed, thanks Conrad!

[nemesis]

So back to my original answer to every Legacy exhaust question. Zerosports downpipe and HKS Hi-Power Silent!

[cacasplat3]

[quote="Conrad"]An excerpt I have always kept at hand that may be applicable to what you guys are looking at.



The following excerpts are from Jay Kavanaugh, a turbocharger development engineer for Garrett Engine Boosting Systems, responding to a thread on Impreza.net, regarding exhaust design and exhaust theory:

“Howdy,

This thread was brought to my attention by a friend of mine in hopes of shedding some light on the issue of exhaust size selection for turbocharged vehicles. Most of the facts have been covered already. FWIW I'm an turbocharger development engineer for Garrett Engine Boosting Systems.

N/A cars: As most of you know, the design of turbo exhaust systems runs counter to exhaust design for n/a vehicles. N/A cars utilize exhaust velocity (not backpressure) in the collector to aid in scavenging other cylinders during the blowdown process. It just so happens that to get the appropriate velocity, you have to squeeze down the diameter of the discharge of the collector (aka the exhaust), which also induces backpressure. The backpressure is an undesirable byproduct of the desire to have a certain degree of exhaust velocity. Go too big, and you lose velocity and its associated beneficial scavenging effect. Too small and the backpressure skyrockets, more than offsetting any gain made by scavenging. There is a happy medium here.

For turbo cars, you throw all that out the window. You want the exhaust velocity to be high upstream of the turbine (i.e. in the header). You'll notice that primaries of turbo headers are smaller diameter than those of an n/a car of two-thirds the horsepower. The idea is to get the exhaust velocity up quickly, to get the turbo spooling as early as possible. Here, getting the boost up early is a much more effective way to torque than playing with tuned primary lengths and scavenging. The scavenging effects are small compared to what you'd get if you just got boost sooner instead. You have a turbo; you want boost. Just don't go so small on the header's primary diameter that you choke off the high end.

Downstream of the turbine (aka the turboback exhaust), you want the least backpressure possible. No ifs, ands, or buts. Stick a Hoover on the tailpipe if you can. The general rule of "larger is better" (to the point of diminishing returns) of turboback exhausts is valid. Here, the idea is to minimize the pressure downstream of the turbine in order to make the most effective use of the pressure that is being generated upstream of the turbine. Remember, a turbine operates via a pressure ratio. For a given turbine inlet pressure, you will get the highest pressure ratio across the turbine when you have the lowest possible discharge pressure. This means the turbine is able to do the most amount of work possible (i.e. drive the compressor and make boost) with the available inlet pressure.

Again, less pressure downstream of the turbine is goodness. This approach minimizes the time-to-boost (maximizes boost response) and will improve engine VE throughout the rev range.

As for 2.5" vs. 3.0", the "best" turboback exhaust depends on the amount of flow, or horsepower. At 250 hp, 2.5" is fine. Going to 3" at this power level won't get you much, if anything, other than a louder exhaust note. 300 hp and you're definitely suboptimal with 2.5". For 400-450 hp, even 3" is on the small side.â€

[25stouring]

Hey guys
Just bumping this thread to ask a few quick questions on my LGT's exhaust.
I have a bone stock 05 which i really dont plan on modifying but would like to extract a slightly lower rumble than stock.
I want to install the Hks silent high power exhaust (31019-AF019) on the vehicle and keep up pipe, down pipe and their associated cats stock.
I want to know what modifications would be necessary to install the part as listed above which is US spec I think. ALso will there be any conflicting issues with o2 sensors and CELs coming up afterwards ,is it possible to purchase just the silent hi power cans alone without the piping to be installed on my stock piping and finally will this require me to tune the car afterwards?
Again I am not looking for any performance gains from this and car is not daily driven.


Thanks

[VexXx Dogg]

not seeking perf gains?
why not look for a pair of STI Genome barrels to swap on? leave downpipe and midpipe as is.

[25stouring]

might either go with that or a pair of perrin street tones

[VexXx Dogg]

finally did my exhaust upgrade.

bought a pair of magnaflow race core barrels (3" inlet 4" out w/ full 3" core).
Ran 3" from downpipe splitting into 2 2.5" to the barrels. Crush bends tho, but bang for buck factor won out here. I did not want to spend 8K for a farley spec exhaust. It looks hot and I'm sure it performs like a beyotch but realistically not worth the cost to ME.

No resonator because I couldnt get a 3" core resonator at the time.

I absolutely refuse to dyno until I get my FMIC, raise boost and retune.

for now the noise is phenomenal

[BZ]

glad yr happy with it bro.........you can have the resonator made if you want though.

[Monk BANzai]

bump...i need a number for Farley's (am assuming he's local).....

help much?

[copper_shot]

expect to spend 8k

for a full stainless steel set up...

492-0164

[Monk BANzai]

thanks....