Eliminating upper Cat on stock downpipe?? - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

dued · 06-21-2010, 04:42 PM

Car: 1995 S14

Hi, this might be a dumb question but here it goes: I currently have a stock header, stock downpipe, and stock cat with a 3" cat-back exhaust.

I noticed that the stock downpipe has a cat at the top of it, and a stock cat at the end of the downpipe. So I was thinking if I were to buy an aftermarket downpipe + test pipe, would the downpipe eliminate the upper cat? I know that the test pipe will eliminate the final cat, but my goal is to eliminate both.

!Zar! · 06-21-2010, 06:07 PM

The cat at the center is hollow on s14's. So a test pipe would be worthless.

Only the cat on the downpipe is an actual functioning cat.

nismoracingsx · 06-22-2010, 02:35 PM

Why would you want to eliminate both cats, and don't say for hp, for the love of god >.<

murda-c · 06-22-2010, 02:41 PM

Quote:

Originally Posted by !Zar!

The cat at the center is hollow on s14's. So a test pipe would be worthless.

Only the cat on the downpipe is an actual functioning cat.

My car had a cat there

dawagarage · 06-22-2010, 03:43 PM

does your car not have to pass CA emissions? if yes, how do you intend to do so with your cat removed? as for the 'pre-cat', i think its purpose is to serve as a noise reducer/resonator. when i replaced my stock exhaust manifold with a used hotshot header i scored off ebay, the car was noticably louder. i dont think youre going to find ka24de downpipes, etc. you should just replace the whole exhaust manifold, thus gaining power and eliminating the precat.
i heard DC was very good, yet discontinued, yet somehow theyre available here:
DC SPORTS 4-2-1 RACE HEADERS 95-98 NISSAN 240SX : eBay Motors (item 170472885151 end time Jul-13-10 00:15:20 PDT)
failing that, try to acquire a hotshot or pacesetter header.

!Zar! · 06-22-2010, 05:40 PM

Quote:

Originally Posted by murda-c

My car had a cat there

Really? My s14 had a hollow cat on the bottom, and a fully functional honeycomb cat on the downpipe.

Same with another s14 I worked on.

I could be wrong. Maybe both just happened to have no center cat in my case?

murda-c · 06-24-2010, 07:56 AM

Oh i think it might be because my car is OBDII.

That's probably it.

sirfallsalot243 · 06-24-2010, 08:20 AM

Quote:

Originally Posted by !Zar!

Really? My s14 had a hollow cat on the bottom, and a fully functional honeycomb cat on the downpipe.

Same with another s14 I worked on.

I could be wrong. Maybe both just happened to have no center cat in my case?

No, youre right. My S14 came with a hollow second cat. I would assume its because thats where the real cat would be on factory SR20 S14's, and since we got the KA with a cat in the downpipe, Nissan just threw an "oem testpipe" there. Every S14 ive worked on has been this way, OBD2 or not.

Homer_Simpson · 06-24-2010, 10:04 AM

Quote:

Originally Posted by sirfallsalot243

No, youre right. My S14 came with a hollow second cat. I would assume its because thats where the real cat would be on factory SR20 S14's, and since we got the KA with a cat in the downpipe, Nissan just threw an "oem testpipe" there. Every S14 ive worked on has been this way, OBD2 or not.

My 95 does not have a hollow secondary catalytic converter. I was expecting a hollow cat when I bought the car but it was full of honeycomb.

sirfallsalot243 · 06-24-2010, 10:38 AM

Interesting. I've only done exhaust work on 1 OBD1 S14, maybe it was already gutted when I got to it. I know my car's exhaust wasnt touched before me (obd2) and it had a hollow 2nd cat.

***S14DB*** · 06-24-2010, 10:46 AM

Federal cars have only the primary cat. California (CARB) cars have a secondary cat.

Homer_Simpson · 06-24-2010, 11:21 AM

Quote:

Originally Posted by S14DB

Federal cars have only the primary cat. California (CARB) cars have a secondary cat.

That make sense, I totally forgot about it being a CA car.

sirfallsalot243 · 06-24-2010, 11:29 AM

Quote:

Originally Posted by Homer_Simpson

That make sense, I totally forgot about it being a CA car.

And would also explain why ive never run into an s14 with a secondary cat.

Not too many CA cars make it out here to PA.

SHINCHU · 06-24-2010, 10:59 PM

i have a CA 95 with a honeycomb cat that unbolts from the downpipe. i could put on my SR test pipe if i want. no pre-cat.
however i might try to hunt down a CA OBD-II pre-cat style manifold if i have trouble passing smog? hmm... good thread.

projectRDM · 06-25-2010, 07:57 AM

SR downpipe and RT cat bolts right to the OE manifold, or buy a header and any aftermarket cat.

We've talked about this since 1995. Nothing has changed.

*DALAZ_68* · 06-25-2010, 07:59 AM

Quote:

Originally Posted by projectRDM

We've talked about this since 1995. Nothing has changed.

except for the crowd sir...

!Zar! · 06-26-2010, 01:52 PM

Quote:

Originally Posted by DALAZ_68

except for the crowd sir...

You're right.

They are even more lazy, and dumber than before.

06-21-2010, 04:42 PM	#1
dued Zilvia Junkie Join Date: Dec 2005 Location: Vista, CA Posts: 450 Trader Rating: (3) Feedback Score: 3 reviews	Eliminating upper Cat on stock downpipe?? Car: 1995 S14 Hi, this might be a dumb question but here it goes: I currently have a stock header, stock downpipe, and stock cat with a 3" cat-back exhaust. I noticed that the stock downpipe has a cat at the top of it, and a stock cat at the end of the downpipe. So I was thinking if I were to buy an aftermarket downpipe + test pipe, would the downpipe eliminate the upper cat? I know that the test pipe will eliminate the final cat, but my goal is to eliminate both.

06-21-2010, 06:07 PM	#2
!Zar! Post Whore! Join Date: Nov 2004 Location: North Korea Posts: 14,579 Trader Rating: (27) Feedback Score: 27 reviews	The cat at the center is hollow on s14's. So a test pipe would be worthless. Only the cat on the downpipe is an actual functioning cat. __________________

06-24-2010, 07:56 AM	#7
murda-c Post Whore! Join Date: Jan 2007 Location: Montgomery County, MD Age: 37 Posts: 3,198 Trader Rating: (1) Feedback Score: 1 reviews	Oh i think it might be because my car is OBDII. That's probably it. __________________

06-24-2010, 10:46 AM	#11
*S14DB* AFC #1 Join Date: Oct 2003 Location: 昨晩あなたのお母さんの家 Posts: 20,181 Trader Rating: (3) Feedback Score: 3 reviews	Federal cars have only the primary cat. California (CARB) cars have a secondary cat. __________________ Comments should be taken as Opinions not as Statements of Fact

06-25-2010, 07:57 AM	#15
projectRDM Post Whore! Join Date: Dec 2002 Location: Atlanta Age: 51 Posts: 13,812 Trader Rating: (12) Feedback Score: 12 reviews	SR downpipe and RT cat bolts right to the OE manifold, or buy a header and any aftermarket cat. We've talked about this since 1995. Nothing has changed. __________________ FORMERLY R240NA Learn what's really going on and protect your assets now before they're gone forever: www.paypalsucks.com

06-22-2010, 02:35 PM	#3
nismoracingsx Zilvia Addict Join Date: Sep 2007 Location: Alachua, FL Age: 38 Posts: 969 Trader Rating: (32) Feedback Score: 32 reviews	Why would you want to eliminate both cats, and don't say for hp, for the love of god >.<

06-22-2010, 03:43 PM	#5
dawagarage Nissanaholic! Join Date: Sep 2006 Location: Bremerton, WA Age: 40 Posts: 2,037 Trader Rating: (23) Feedback Score: 23 reviews	does your car not have to pass CA emissions? if yes, how do you intend to do so with your cat removed? as for the 'pre-cat', i think its purpose is to serve as a noise reducer/resonator. when i replaced my stock exhaust manifold with a used hotshot header i scored off ebay, the car was noticably louder. i dont think youre going to find ka24de downpipes, etc. you should just replace the whole exhaust manifold, thus gaining power and eliminating the precat. i heard DC was very good, yet discontinued, yet somehow theyre available here: DC SPORTS 4-2-1 RACE HEADERS 95-98 NISSAN 240SX : eBay Motors (item 170472885151 end time Jul-13-10 00:15:20 PDT) failing that, try to acquire a hotshot or pacesetter header.

06-24-2010, 10:38 AM	#10
sirfallsalot243 BANNED Join Date: Nov 2007 Location: Doylestown, PA Age: 37 Posts: 468 Trader Rating: (3) Feedback Score: 3 reviews	Interesting. I've only done exhaust work on 1 OBD1 S14, maybe it was already gutted when I got to it. I know my car's exhaust wasnt touched before me (obd2) and it had a hollow 2nd cat.

06-24-2010, 10:59 PM	#14
SHINCHU Zilvia Member Join Date: Nov 2002 Location: Temecula, CA Age: 45 Posts: 244 Trader Rating: (0) Rides Gallery: SHINCHU Feedback Score: 0 reviews	i have a CA 95 with a honeycomb cat that unbolts from the downpipe. i could put on my SR test pipe if i want. no pre-cat. however i might try to hunt down a CA OBD-II pre-cat style manifold if i have trouble passing smog? hmm... good thread.