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Gutting catalytic converters?


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Hi All,

I have a 97 Legacy GTB twin turbo, I would like to improve fuel economy and power by gutting my catalytic converters. Apparently you can smash the guts out of them with a suitable rod/broom handle/whatever and leave them in place?

What I want to know is:

Will my exhaust get any louder?

Any WOF issues?

Will either of my turbos overboost?

Any ECU/warning light issues?

Is it easy enough to do?

Any thing else I should be aware of?

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 WRXONP']

[quote name='caged said:

And kill dolphins/small children and make our summer warmer ;D

/quote]

does ur 406 WHP run a cat?

Na im more a dog man, hotdog all the way. :P. I only drive my car too the track and my anti lag would kill a cat. Fair call though lol

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I've heard you shouldn't remove the primary turbo cat as it'll make that little sucker over spool and shorten its life dramaticly. I removed my secondary cat on my old legacy when I got a new exhaust made. It went better but certainly didn't use less gas.

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Thanks Stoffa,

so from memory there are 3 cats in total, one after each turbo and then one after the Y. Would you recommend I remove both the cat after the secondary and the last one after the Y, or just one of them and not both?

Oh and was your car thirstier because you were using the extra power after removing the cat, or did removing the cat actually make it thirstier when cruising?

Cheers

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If you have a twin turbo, you risk over spooling the turbos if you remove any of the cats on the dumps without a tune.

Personally, I think its very ghetto style. Your just ruining the environment for a few kilowatts. Your car will definitely not meet local emission standards and will stink.

If you want more power, do it properly and within the limits of the law. A full exhaust will give you more power, then there is a list of other mods you can do to add a few more ponies. You can also buy a high flow cat that will give you what you want. A high flowing exhaust wont give you better fuel economy. The increased air flow through the engine will probably increase your fuel consumption. If you want to increase your fuel economy, and assuming it is getting bad economy when compared to other Legacy's, you will want to do a full service, replace all fiilters and oil and check for potential issues.

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 WRXONP said:

id beg to differ that though (not on a twin turbo tho) but on my rex i replaced exhaust with a high flow straight through and it saved me gas because u use waaaay less throttle to go everywhere and turbo spools waaay earlier....

Slow down sunshine the difference is good but not that good

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  • General Member

lol TT/fuel economy in same sentance...

(and/or ANY turbo/subaru at the same time)

increase air pressure in tires 36-40?PSI - carry as less weight as possible : keep fuel tank under half/no subs/boxes etc

dont accelerate or brake heavily (braking heavily means you were goin to fast in 1st place)

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OK, so sounds like I should stay away from the cat in the down pipe to avoid over spooling the primary turbo, but am thinking I can get away with gutting the second cat after the downpipes.

Thanks for the info BigWillieStyles (seriously) but I don't subscribe to the "making your engine breathe more efficiently won't save you gas" theory. I have done cold air intakes and changed mufflers and pipes before and noticed the savings, so still keen to move ahead.

Also the emissions regs are for cars first registered after 2010 so being a 1997 model my car is not subject to current regs.

Does anyone know if there is an exhaust gas sensor on the second cat converter? I don't want the ECU to throw a code if I mess with anything upstream of a sensor.

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Ok, so had a look under the car and there is a sensor on both cats, the one after the primary turbo and the one further downstream in the main exhaust.

Does this mean that even just gutting the second cat will trigger a check engine light?

Cheers for any help

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further down the track CATs will be on the radar with emissions etc.

Have you thought of replacing your probably dead cats with performance high flow versions?

Should result in a little better flow, no over spool and compliant emissions.

Win all around?

(apart from wallet)

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to my understanding of the cat convertor is that the wires going into it are not a sensor as such but are a "heater" element...sort of like a glow plug as such...

some Cats have extra o2 sensors though to make sure the cat is actually doing its job...not sure if this is on a subaru though

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