downstream second cat removal

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

Moderators: Helpinators, Moderators

Post Reply
JohnP
In Neutral
Posts: 13
Joined: Sat May 10, 2014 3:40 pm

downstream second cat removal

Post by JohnP » Fri Jul 11, 2014 8:35 pm

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
Fifth Gear
Posts: 2267
Joined: Fri May 04, 2007 4:09 pm
Location: N. ID

Re: downstream second cat removal

Post by wtdash » Sun Jul 13, 2014 4:52 am

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 4WD Wagon (pre-Loyale) - SOLD
'90 BJ, EJ22T/DOHC and 5-speed swap - SOLD
'04 FXT, Forged internals, VF39, STI TMIC, Cobb AP- SOLD
'93 Legacy SS - 5-speed, SOLD :-(
'02 WRX GG-SOLD
'96 BD - turbo'd-SOLD

rallyak
Third Gear
Posts: 895
Joined: Wed Oct 26, 2011 7:02 am
Location: Anchorage,Alaska

Re: downstream second cat removal

Post by rallyak » Sun Jul 13, 2014 7:00 am

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
Fifth Gear
Posts: 6305
Joined: Fri Jun 20, 2008 8:17 am
Location: Lakewood, Wa 98439
Contact:

Re: downstream second cat removal

Post by cj91legss » Mon Jul 14, 2014 1:20 pm

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
Moderator
Moderator
Posts: 4873
Joined: Tue Aug 25, 2009 7:52 am
Location: Des Moines, Wa

Re: downstream second cat removal

Post by mike-tracy » Wed Jul 16, 2014 2:29 am

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
Posts: 111
Joined: Wed Mar 10, 2010 11:37 pm

Re: downstream second cat removal

Post by czei » Sat Sep 13, 2014 1:46 pm

When the 2nd cat is removed, what happens to the oxygen sensor? Just take it off?

wtdash
Fifth Gear
Posts: 2267
Joined: Fri May 04, 2007 4:09 pm
Location: N. ID

Re: downstream second cat removal

Post by wtdash » Sat Sep 13, 2014 1:59 pm

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 4WD Wagon (pre-Loyale) - SOLD
'90 BJ, EJ22T/DOHC and 5-speed swap - SOLD
'04 FXT, Forged internals, VF39, STI TMIC, Cobb AP- SOLD
'93 Legacy SS - 5-speed, SOLD :-(
'02 WRX GG-SOLD
'96 BD - turbo'd-SOLD

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 » Fri Jan 16, 2015 11:02 pm

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
Fifth Gear
Posts: 6305
Joined: Fri Jun 20, 2008 8:17 am
Location: Lakewood, Wa 98439
Contact:

Re: downstream second cat removal

Post by cj91legss » Sat Jan 17, 2015 4:46 pm

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 » Sat Jan 17, 2015 6:34 pm

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

Post Reply