RS Liberty muffer/exhaust mods, info
Posted: Thu Feb 01, 2001 3:29 am
For those of you that have an RS Liberty you will find the following
very
> interesting.... even rex owners may have an interest...afterall it
concerns
> a wrx rear muffler. The reason for below mods, i have family living in
the
> snowy mountains and commute quite regulary from Sydney. My wife did not
like
> the extra noise from my 3" system. ps i have to sit next to her for more
> than 5 hours for this trip.
>
> 1. First before i start, my car: 1992 RS Liberty sedan, has a
complete
> turbo back 3" mrt s/s system fitted. (Great system might i add.) A
'Festo'
> bleed type valve for added boost with a fuel cut defender, resonator
> removed, with air inlet hole increased in the oem filter box. Boost set
at
> 16psi.
> With this setup the car reached an easy16psi boost. (naturaly as that is
> what i set it at)
> I removed the mrt s/s rear muffler and fitted the std RS Liberty muffler
> back on. I purchased an adapter flange from mrt ($20) so the std muffler
> would bolt up to the 3" mrt turbo back system.
> The first thing i noticed.. very quiet.. can hear wind noise again.... not
> that the mrt system was loud by any means. The other thing i noticed is
> how the car lost power. Also boost was now only "just" reaching 14psi.
> Obviously the exhaust restriction, back pressure, has the turbo not
spinning
> as freely, deffinite difference.
>
> 2. Next i purchased a used wrx muffler off mrt, $50. It was off an 11/97
> wrx. The difference between the RS Liberty muffler and the rex muffler was
> immediatley noticeable.
> a) The overall size alone of the wrx muffler is shorter. Also the inlet
pipe
> going into the muffler on the RS is 1 3/4" (45mm) I.D.
> On the rex the I.D. pipe is 2 1/4" (56mm), thats 11mm bigger I.D. for the
> wrx.
> b).The twin outlet pipes on the RS may look like they are 1 5/8"
(40mm)I.D.
> but they are swaged down to 1 1/4" (32mm) near the tips.
> The wrx is 1 5/8" (40mm) with NO swage.
>
> 3. I cut the RS muffler open. it gets worse. The 1 1/4" (32mm) swage at
> the tips is actually the size of both the entire internal outlet pipes.
The
> wrx is 40mm constant right through. This alone gives an I.D increase of
8mm
> on EACH outlet pipe, times this by two, big difference. Not only that but
> in the picture of the wrx muffler, (picture attached) you will see how
the
> gases split in two directions, half the gases flow through the long
internal
> pipe going from chamber 2 to chamber 4 , then back through the hole in the
> seperator (baffle) to chamber 3 etc. On the RS muffler there is NO hole in
> the seperator. The gases enter into chamber 4 with nowhere to go!
> Rediculous!. talk about 'choked' up.
>
> In summary ..... the wrx muffler has a larger inlet pipe by 11mm, better
> flowing internals with the hole in the seperator(baffle), and the two
> internal, leading outlet, pipes are larger by 8mm EACH., I.D.
> 4. So i took the wrx muffler to my local exhaust shop who modified it to
> fit to my Lberty. He cut off the original inlet pipe to the muffler,
(angles
> are different), and made a whole new 2 1/2" pipe welded to the muffler on
> one end and with the mrt adaptor welded to it, to bolt onto my mrt system,
> on the other. Also needed to modify one of the hanger brkts. Cost me $50
for
> the
> whole job.
>
> The results......... my car now boosts again at 16psi and has power again
> ......and is QUIET.
> Overall I think if you own a Liberty RS, a good compromise is to fit a
late
> model wrx rear muffler with a good turbo back system, you will end up with
> good power, std look (chrome outlet on wrx is also better looking than
the
> RS) and is quiet. Maybe someone should do a dyno test on a late model wrx
> keeping the oem muffler but replacing the exhaust from turbo back up to
the
> rear muffler.
> It maybe suprising. For those that want out and out performance obviously
> the rear muffler would help more but by how much ???????
> The Liberty muffler isn't worth the work to modify, Which is what i was
> going to do. I would need to replace the whole internals ..pipes etc..so
> in the bin with that one ......
> Subaru lists the std wrx with a slighty higher output rating than the std
RS
> Liberty, perhaps this muffler mod by subaru is 'part' of the reason for
it.
> Subaru have obviously worked on a less restrictive muffler. No wonder a
rear
> muffler mod on the RS Liberty made such a huge difference. Overall cost,
> muffler $50, flange $20, work $50 , total $120.
> Regards, Rod.
>
>
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very
> interesting.... even rex owners may have an interest...afterall it
concerns
> a wrx rear muffler. The reason for below mods, i have family living in
the
> snowy mountains and commute quite regulary from Sydney. My wife did not
like
> the extra noise from my 3" system. ps i have to sit next to her for more
> than 5 hours for this trip.
>
> 1. First before i start, my car: 1992 RS Liberty sedan, has a
complete
> turbo back 3" mrt s/s system fitted. (Great system might i add.) A
'Festo'
> bleed type valve for added boost with a fuel cut defender, resonator
> removed, with air inlet hole increased in the oem filter box. Boost set
at
> 16psi.
> With this setup the car reached an easy16psi boost. (naturaly as that is
> what i set it at)
> I removed the mrt s/s rear muffler and fitted the std RS Liberty muffler
> back on. I purchased an adapter flange from mrt ($20) so the std muffler
> would bolt up to the 3" mrt turbo back system.
> The first thing i noticed.. very quiet.. can hear wind noise again.... not
> that the mrt system was loud by any means. The other thing i noticed is
> how the car lost power. Also boost was now only "just" reaching 14psi.
> Obviously the exhaust restriction, back pressure, has the turbo not
spinning
> as freely, deffinite difference.
>
> 2. Next i purchased a used wrx muffler off mrt, $50. It was off an 11/97
> wrx. The difference between the RS Liberty muffler and the rex muffler was
> immediatley noticeable.
> a) The overall size alone of the wrx muffler is shorter. Also the inlet
pipe
> going into the muffler on the RS is 1 3/4" (45mm) I.D.
> On the rex the I.D. pipe is 2 1/4" (56mm), thats 11mm bigger I.D. for the
> wrx.
> b).The twin outlet pipes on the RS may look like they are 1 5/8"
(40mm)I.D.
> but they are swaged down to 1 1/4" (32mm) near the tips.
> The wrx is 1 5/8" (40mm) with NO swage.
>
> 3. I cut the RS muffler open. it gets worse. The 1 1/4" (32mm) swage at
> the tips is actually the size of both the entire internal outlet pipes.
The
> wrx is 40mm constant right through. This alone gives an I.D increase of
8mm
> on EACH outlet pipe, times this by two, big difference. Not only that but
> in the picture of the wrx muffler, (picture attached) you will see how
the
> gases split in two directions, half the gases flow through the long
internal
> pipe going from chamber 2 to chamber 4 , then back through the hole in the
> seperator (baffle) to chamber 3 etc. On the RS muffler there is NO hole in
> the seperator. The gases enter into chamber 4 with nowhere to go!
> Rediculous!. talk about 'choked' up.
>
> In summary ..... the wrx muffler has a larger inlet pipe by 11mm, better
> flowing internals with the hole in the seperator(baffle), and the two
> internal, leading outlet, pipes are larger by 8mm EACH., I.D.
> 4. So i took the wrx muffler to my local exhaust shop who modified it to
> fit to my Lberty. He cut off the original inlet pipe to the muffler,
(angles
> are different), and made a whole new 2 1/2" pipe welded to the muffler on
> one end and with the mrt adaptor welded to it, to bolt onto my mrt system,
> on the other. Also needed to modify one of the hanger brkts. Cost me $50
for
> the
> whole job.
>
> The results......... my car now boosts again at 16psi and has power again
> ......and is QUIET.
> Overall I think if you own a Liberty RS, a good compromise is to fit a
late
> model wrx rear muffler with a good turbo back system, you will end up with
> good power, std look (chrome outlet on wrx is also better looking than
the
> RS) and is quiet. Maybe someone should do a dyno test on a late model wrx
> keeping the oem muffler but replacing the exhaust from turbo back up to
the
> rear muffler.
> It maybe suprising. For those that want out and out performance obviously
> the rear muffler would help more but by how much ???????
> The Liberty muffler isn't worth the work to modify, Which is what i was
> going to do. I would need to replace the whole internals ..pipes etc..so
> in the bin with that one ......
> Subaru lists the std wrx with a slighty higher output rating than the std
RS
> Liberty, perhaps this muffler mod by subaru is 'part' of the reason for
it.
> Subaru have obviously worked on a less restrictive muffler. No wonder a
rear
> muffler mod on the RS Liberty made such a huge difference. Overall cost,
> muffler $50, flange $20, work $50 , total $120.
> Regards, Rod.
>
>
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