club.liberty.asn.au

Hey guys and gals,

I've been looking at exhaust mods for my 2011 Liberty Sports Premium and I was wondering how easy it is to convert it to dual tail pipes like the GT? It has the cutout in the bumper already (a minor issue, I know) but I was wondering how different the exhaust systems are between the turbo and NA models? Would it be an easy conversion, even from a catback or would it be more involved than that?

Beyond that, would anyone have any recommendations on what systems to go with to make it sound a bit more sporty? I understand its hard to make the Libertys (especially the NA ones) sound anything like a WRX but that would be my dream haha.

Thanks

The "WRX note" or "boxer beat" comes from the unequal length headers that were on WRXs - they introduce a particular offbeat "note" due to overlapping exhaust pulses caused by the unequal lengths that exhaust gases travel from the cylinder exhaust valves to the collector.

It's practically impossible to replicate this sound (at least the off-beat part of it) with a car with equal length headers (as I suspect the 5Gen NA engines have). The pre-FL 4Gen GTs had the same issue - they had a twin-scroll turbo and equal-length headers, so they didn't have the "WRX note" either. The post-FL 2.5L GTs have it again, as Subaru switched back to a single scroll turbo and unequal length headers.

As I understand it, the FB engine on the new WRX has equal-length headers as well, though the STI has the older EJ255 motor as I undertand it, and should retain the unequal length headers for the time being. I'd say though that the unequal length headers design has a limited time left before it's dropped completely...

If you have the ej motor, you can get those borla replica ones from the impreza on ebay or even oem uel headers from a 2005? impreza and custom fit them. Some guy in Russia did a dodgy custom job..lol. You can do it on a n/a.. but its a waste of money and time, imo. If you want to do it, then you're more than welcome to!

search the legacy gt forums.. i made a thread about it.

Thanks for the info guys. I kinda guessed it wouldn't be terribly feasible getting it to sound like a WRX.

What about converting to dual exhaust? Would this be any easier?

Thanks.

LibertyJackkk wrote:Thanks for the info guys. I kinda guessed it wouldn't be terribly feasible getting it to sound like a WRX.

What about converting to dual exhaust? Would this be any easier?

Thanks.

The dual-exhaust comes from a split at the rear of the the mid-pipe (often called the Y-pipe) on many cars, 5Gens included or so it seems from this:

http://www.bestmufflers.com/bshop/produ ... a07c244098

Assuming the exhaust pipe routing is the same in a 5Gen with a single exhaust output to the section of the mid-pipe where the 'Y" occurs, and that there's sufficient room under the car for the Y and a second muffler (given the cutout is already in the bumper, I suspect there's room there) and the required mounting points exist (again, I'd be surprised if they were either not there or hard to add if they're not), it shouldn't be difficult to convert from a single outlet to dual. You may even get lucky and pick up the stock Y-pipe and mufflers from someone upgrading to an aftermarket system - its not likely that a 3" after-market system is going to be cost-effective or even desirable on an NA engine (as higher exhaust gas speeds provided by a smaller diameter exhaust system is important for post-combustion scavenging on NA engines).

Thanks for the response Manaz

So assuming what you say is accurate, an exhaust compatible with a GT should fit my car without too much hassle?

As for using a 3" system, I'm sorry but I'm not well versed in the technical side of things but from what you said, do you mean that a larger diameter exhaust would likely blunt the performance of the NA engine rather than enhance or not effect it?

LibertyJackkk wrote:Thanks for the response Manaz

So assuming what you say is accurate, an exhaust compatible with a GT should fit my car without too much hassle?

Yep, if what I say is accurate (noting that I'm talking based on a theoretical understanding of the 5Gen, not actually getting up underneath one), then yes.

As for using a 3" system, I'm sorry but I'm not well versed in the technical side of things but from what you said, do you mean that a larger diameter exhaust would likely blunt the performance of the NA engine rather than enhance or not effect it?

That's correct. Exhaust gases flow down a large exhaust system at lower velocity. This can mean that scavenging of exhaust gases (where the flow effectively "sucks" exhaust gases out of the cylinder) from the cylinder may be incomplete, which leads to less room for intake charge (and thus less intake charge in the cylinder for combustion). And if you burn less intake charge, you make less power.

Scavenging isn't such an issue when forced induction is in place (for a variety of reasons).

Okay cool, thanks for that. So I'll be sure to stick to the same diameter exhaust. Now to track down a GT exhaust haha.