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Old 06-28-2001, 08:45 PM   #1
XBD
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WR Blue

Default Curious about the 3 Cat. converters

Im close to purchasing a WRX (or ordering one)... and Im curious about the stock exhaust,....

What do you all think the implications of having 3 catalytic (prolly misspelled) converters is?

I know normal they restrict exhaust flow when there is only 1 of them,...but the WRX has 3 right? that gonna really restrict the flow?

Also I know as some Cat. converters age sometimes they sorta melt inside and performance is degraded...this gonna be 3 fold or something similar on the WRX?

Is there any point on putting a performance exhaust system on after the 3 converters if thats the only section you ugrade? i.e. muffler or something (in terms of power gain)

The 3 converters is so it passes american emission standards right? if so if you remove one or more it gonna make you flunk a emissions inspection?

Thanks in advance
XBD
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Last edited by XBD; 06-28-2001 at 08:56 PM.
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Old 06-28-2001, 10:32 PM   #2
Dori Dori
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3 cats. One before the turbo on the exhaust manifold (header) and two after.

Buy a turbo back exhaust and both will be replaced w/ one high flow cat.

A new set of headers will eliminate the one before the turbo.

A cat-back exhaust will only replace one cat (the last one) with a high flow cat. To eliminate the 2'nd one, you'll need to replace your downpipe.

Of course they are restrictive and I have heard people (i really have) say "take off the cats and you'll have 340hp". This is of course untrue. Who knows how much of a gain you would have w/out them in place b/c most exhaust (turbo back that is) systems remove them and add the better exhaust piping. If I had to guess though prob (all three) 20-30hp.
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Old 06-28-2001, 10:46 PM   #3
XBD
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That sounds like that will really simplfy the exhaust and improve flow....will it pass emissions like that?

Whyd they slap on 3 cats in the first place? for emissions?

Also how much (ball park) would the above you describe cost to do?

Last edited by XBD; 06-28-2001 at 11:06 PM.
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Old 06-29-2001, 12:28 AM   #4
illmatic
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3" turbo back exhaust usually range around $900-1500 depending on what you get. Vishnu up-pipe will run you around $280.
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Old 06-29-2001, 12:42 AM   #5
jmott
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You could get an aftermarket exauhst with a single hi-flow cat and still pass emissions in most states.
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Old 06-29-2001, 09:26 AM   #6
Tuning Factory Inc.
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Turbos and cats do not mix period. Cat backs will not touch any of your 3 cats. I have removed the last cat due to fitment problems installing a JDM spec exhaust. It is not a huge difference. The front one and the first rear will probably net bigger gains in response and power. I also estimate around 20-30 hp. Just as a sidenote, many turbo cars pass with no cats whatsoever. My old Celica All trac turbo had numorous reports of passing emmissions with no cats at all.
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Old 06-29-2001, 09:37 AM   #7
Dori Dori
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I guess thats why its called a cat back. Woops
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Old 06-29-2001, 12:44 PM   #8
Akirasoft
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One of the other things about the WRX and cats is this, the Turbo provides sufficient backpressure that removing the cats and going with a larger diameter exhaust actually helps. In lots of other vehicles making those same changes is detrimental to performance due to lack of backpressure...
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Old 06-29-2001, 03:28 PM   #9
nqwan
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Quote:
Whyd they slap on 3 cats in the first place? for emissions?
the rex didnt need all the cats that it has, subaru threw them all on to make it a low emissions vehicle
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