downstream second cat removal

Headers, cats, uppipes, downpipes, midpipes and mufflers.

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JohnP
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Joined: Sat May 10, 2014 3:40 pm

downstream second cat removal

Post by JohnP »

I have read the upstream 2-into-1 catalytic converters should be kept what about the second downstream catalytic converter any better benefits from removing it?
wtdash
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Re: downstream second cat removal

Post by wtdash »

Hi,
Depends on your mods. I recently removed mine as part of a 3" exhaust upgrade and my dyno #'s definitely went up. But I'm also running a bigger turbo/injectors/more boost.
TD
Turbo Subies:
'87 GL-10 Turbo - SOLD
'90 BJ EJ22T/DOHC & 5speed swap - SOLD
'04 FXT, Forged internals, VF39, STI TMIC, Cobb AP- SOLD
'93 Legacy SS - 5-speed, SOLD :-(
'02 WRX -SOLD
'96 BD-turbo'd-SOLD
'98 SF - NA-T
rallyak
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Re: downstream second cat removal

Post by rallyak »

I removed mine also when installed stainless headers.
Charles

90' White/Gray Outback DD workhorse (670,xxx) miles
92' Onyx Metallic (430,xxx) Wife's DD
68' Barracuda formula S 340 4spd coupe (ongoing project)
66' Mustang 2+2 4spd wife's (ongoing project)
cj91legss
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Re: downstream second cat removal

Post by cj91legss »

haven't had a cat since 2006
91 L-TW Wagon with a full Swap -RIP
92 SS Prefaced, GD dash swapped, 22T/205 Hybrid 20 psi - BEAST!
93 SS Bone Stock Gone!
94 TW Bone Stock Gone!
91 SS 4EAT Sold!
98 LGT 4EAT
98 LGT Wagon 4EAT
mike-tracy
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Re: downstream second cat removal

Post by mike-tracy »

I don't think removing the second cat on a stock engine setup will make a huge difference in the scheme of things, but if you have more upgrades planned for later I don't think it could hurt.
1992 Legacy SS 5mt, build in progress
Josh Colombo wrote: Mon Jan 14, 2002 10:23 am Wait....I'm confused now.
czei
First Gear
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Joined: Wed Mar 10, 2010 11:37 pm

Re: downstream second cat removal

Post by czei »

When the 2nd cat is removed, what happens to the oxygen sensor? Just take it off?
wtdash
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Joined: Fri May 04, 2007 4:09 pm
Location: N. ID

Re: downstream second cat removal

Post by wtdash »

There is no O2 sensor in the second cat on the first GEN legacies just up by the turbo.
Td
Turbo Subies:
'87 GL-10 Turbo - SOLD
'90 BJ EJ22T/DOHC & 5speed swap - SOLD
'04 FXT, Forged internals, VF39, STI TMIC, Cobb AP- SOLD
'93 Legacy SS - 5-speed, SOLD :-(
'02 WRX -SOLD
'96 BD-turbo'd-SOLD
'98 SF - NA-T
GTEASER
First Gear
Posts: 162
Joined: Thu Sep 18, 2014 5:12 pm
Location: SF Bay Area, CA

Re: downstream second cat removal

Post by GTEASER »

Does anyone know what the size and thread pitch is for the factory o2 sensor? I need to add a bung at the stock location on my newly purchased Invidia Bellmouth Catless DP.
cj91legss
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Re: downstream second cat removal

Post by cj91legss »

They're mostly the same. Any exhaust shop will have them for around 10 bucks.
91 L-TW Wagon with a full Swap -RIP
92 SS Prefaced, GD dash swapped, 22T/205 Hybrid 20 psi - BEAST!
93 SS Bone Stock Gone!
94 TW Bone Stock Gone!
91 SS 4EAT Sold!
98 LGT 4EAT
98 LGT Wagon 4EAT
GTEASER
First Gear
Posts: 162
Joined: Thu Sep 18, 2014 5:12 pm
Location: SF Bay Area, CA

Re: downstream second cat removal

Post by GTEASER »

Got it thanks. It appears that the standard size is M18x1.5.
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