Twin exhaust vs single

The STI has a single all the way back and the LGT has twin - any advantages either way?

 

Aftermarket guys all seem to be twin for the LGT.

 

Cheers!

LGT still runs a single pipe out to the dual mufflers. Anyone could modify their exhuast on the GT to have just one muffler like how the STi and WRXs have it. With dual mufflers, you can muffle the engine/exhaust noise more but gain some weight in the process.. vice versa on the the single exhuast exit.

 

Most aftermarket GT exhausts are twin because of mainly for looks (to keep the car remaining symmetrical.. I dont think a lot of people like a bumper to have two muffler tip cutouts when you only see one muffler).

 

Keefe

Moved to Turbo Powertrains.

The name of the game is air vs. air out. One large single exh is better than a dual split system because you have more ehx flow and less back pressure due to bends and curves in the piping on a dual setup.

thanks for both replies - makes sense.

But I still think the dual setup looks alot better than a single large muffler.

Dual= much nicer looking.

According to Apexjapan, the dual on our cars isn't less efficient than the single.

Maybe not on our cars because some setups require backpressure for proper tuning. I was just stating in general big Hp numbers come from straight exh setup.

Doesn't it depend on the individual setup? What about a "true" dual exhaust from the engine back, none of this split the pipe halfway back. I think it more depends on the type of engine and what its internals are for the assessment of what the best exhaust setup is.

Thats what I mean. If you have a V type setup that can handle dual exh then it is better. But it really depends on how much air you bring in and combust and how fast you can get it out. If you have a big Hp car and a dual to single exh setup then you are restricting your motor from making more power.

Doesn't it depend on the individual setup? What about a "true" dual exhaust from the engine back, none of this split the pipe halfway back. I think it more depends on the type of engine and what its internals are for the assessment of what the best exhaust setup is.

 

A true dual exhuast on our cars would require us to have twin turbos each running off each bank of the car and running two seperate exhuast systems for each turbo. Or you can get really fancy and do a sequential turbo system (still uses dual exhuast manifolds for each turbo) and run an "X-pipe" for a mid pipe and then splitting back out to a dual exhuast.

 

You are correct, it really depends on the engine layout and setup, not to mention ECU setups and chassis underbody clearances to run that much piping under the car.

 

Keefe

Doesn't it depend on the individual setup? What about a "true" dual exhaust from the engine back, none of this split the pipe halfway back. I think it more depends on the type of engine and what its internals are for the assessment of what the best exhaust setup is.

A true dual would be easier and cpeeper to do on the 2.5i then the gt. on the i model just headers pipes and back to the mufflers. on the gt the only way to do a true dual would be to make it a twin turbo. don't get me wrong i would love a true dual on a twin turbo, but damn that could get pricey.

 

Damint Keefe you beat me to it

Advantage dual axle-back: can run the same flow with better sound supression capability. Con: a few more bends can slow exhaust gas velocity (the real important issue) just slightly. It's really not that big of a deal though.

 

As Keefe noted, you'd have to do a twin-turbo setup, one for each bank to run a true dual-exhaust from the manifold back, but on a 4-cylinder, it's not worth it, you'd have to have some really small turbine housings because essentially you're spinning those turbos with 1.25L, not 2.5L of displacement. To add to that, all that extra exhaust piping costs more weight (probably another 50-100lbs, very rough guess) and space.

 

An H6 would be the only setup that could truly take advantage of such a setup as the exhaust manifolds winding around the engine would be fairly long and complicated, it would likely be easiest running a single turbo per bank with a short up-pipe and downpipe. From there back, that's up in the air as to do true dual-exhaust all the way back or not.

 

So essentially by converting to a single cat-back, you're going to be making more noise, and flow just slightly better and save like I dunno, maybe 30lbs as a rough guess. Not really saving much. And you've got that exhaust port in the rear bumper cover to cover up too.

 

So much for my analytical approach.

As Keefe noted, you'd have to do a twin-turbo setup, one for each bank to run a true dual-exhaust from the manifold back, but on a 4-cylinder, it's not worth it, you'd have to have some really small turbine housings because essentially you're spinning those turbos with 1.25L, not 2.5L of displacement. To add to that, all that extra exhaust piping costs more weight (probably another 50-100lbs, very rough guess) and space.

Audi does it with 1.35L per turbo, and people are upgrading to much bigger turbo's. As for weight, you should be able to tuck the turbo's in close to each set of exhaust outlets, instead of having this huge manifold.

True Deer killer, if they use equal-length manifolds, that really helps low-end response even with lesser displacement, and I'd imaging they run a smaller turbine too, but I'd really have to look into it if we wanted to get into specifics. But tucking the turbo closer to the manifold is what I had in mind if they did an H6 twin-turbo motor, basically an equal-length cast manifold with short up-pipe, less bends in the DP. Keep the heat lower in the engine bay too. It would lose that typical boxer tone, but gain something a bit sportier.

 

Kinda always mad me wonder why Subaru didn't place the oil pan a little further forward and route the exhaust manifold shorter and around the back of it. Although that would be closer to being under the front diff and I'm not sure if that would bring too much hear into those seals and the casing. *shrug*

 

I'm just always looking for ways to be more efficient. I think Subaru really needs to do a major overhaul of their powertrain platform within the next 5 years to be more efficient, lighter, and more effective.

dual = looks...

 

single = practical, lighter...

 

that is all.

Holy Resurection Batman

yeah, sorry. lol.

And while it's back, it does not boil down to looks. As Sube555 said - two mufflers let you have twice the restriction (quieter) with the same overall flow as a single would have. It's why a 300hp Lexus v8 is dead silent and a typical 300hp import sounds like a buzz saw.

 

You can have full power and no noise too, but most people aren't interested in it and they don't know how to obtain it.

 

Oh yeah, and my finished LGT will trap around 120 and sound no louder than stock, at least not till WOT

You cannot do a true dual exhaust system on a sinlge turbo car, there is only one downpipe, so it cannot be "True"

 

It is possible on V or boxer N/A or TT motors though.

 

Running a dual setup on a 2.5l single turbo is just extra weight, a single 3 inch set up would be more then enough flow. Hell a single 3 is enough for a modifyed N/A magnum 360ci motor producing over 450ftlbs. When you get up around 6.7L or 408ci stroker you need 3.5 single or dual 2.5.

 

On a turbo car the best exhaust is no exhaust. Plain and simple, so who will be the first on an LGT with a 3 inch down pipe turned out behind the passenger front wheel?

But I still think the dual setup looks alot better than a single large muffler.

 

Amen to that

http://legacygt.com/forums/picture.php?albumid=841&pictureid=4472

 

This is my single. It was really difficult to build but I found that it was louder, and made the car obviously a little more unique which was what I was kind of shooting for. I dunno though. I've always been a fan of that giant can on any subi. The first one I was was on an STI before I could even drive...its been love ever since.

Cough, cough!

 

Wow! Way to bump a 5 1/2 year old thread!

 

I can understand wanting unique but big single cans need to stay on WRX's and STi's, IMHO.

 

Cheers!

Sweet, I needed a singlefartcan shot in a dual cutout bumper for the rice thread...

 

EDIT: Pete's response

 

since had a bumper conversion and a single cutout...

That's really what you do is just act like a shitbag on the legacy gt forums?

soooo cool.

 

Apparently someone needs to learn how to behave on the internet

since had a bumper conversion and a single cutout...

That's really what you do is just act like a shitbag on the legacy gt forums?

soooo cool.