6spdscreaminchickin

working on putting long tube headers on at school and with the ory i have no cats so no after cat 02s.... my instructor said that the 02s control the fuel or somethiung and without the rear 02s i'm not going to get the hp gains i'm hoping for. what do you guys think? i figure you have personal expierence with these cars. where as he does not. sorry for the noob question.
thanks,
-Brett

hitmanws6

iTrader: (20)

the lack of O2 sensors will affect the performance. you need to do one of 2 things. you can either weld on some bungs to match the ones on your old manifolds or you can hook up an O2 simulator

96LT1355Z28

iTrader: (2)

Either find a set of O2 simulators or have your pcm tuned, I recommend getting a tune since they can modify it however you want!

BigBadWhitey

iTrader: (3)

I picked up the o2 sims from SpeedInc for 100 bucks. Work like a charm, highly recomended.

billabong08

The O2's before the cat control everything you are worried about. The O2 after the cat is only is there to monitor air coming out of it to ensure the cat is doing it's job. Basically it will only set a SES light to let you know that the cat is bad. It will affect performance in no way.

jhthornley

that his current setup (w/ manifolds I assume) does NOT have the after cat O2 sensors... If that is the case, then there is no need to put any "after cat O2s" w/ your new setup either.

lifeisgood

iTrader: (4)

yea the o2's upstream ( the ones in the actual exhaust manifold) are the only ones you need.
the ones downstream ( behind the cat) do nothing, and only throw a code for ems. purposes.
dont wry bout it

96capricemgr

iTrader: (1)

If your car is a 96-7 and it HAD after cat O2s they have no impact on performance as, just a couple of the guys who replied before me said. I would recommend a tune over sims because you can get performance from a tune and sims is $100 just to shut off a CEL, wouldn't it make more sense to spend a little more and gain performance.

You can NOT use O2 sims BEFORE the cats.

I don't know what hitmanws6 was talking about, then again neither does he.
Put sims up by the manifold and best case scenario is a code that will hurt performance, worst case is improper fueling which can most definetely do harm.

z44ss

iTrader: (1)

thats right no need for 02s after the cat. and if you have a 93-94 maybe 95 not sure, but you wont even set off a cel. i have a 94 and no cel here

96capricemgr

iTrader: (1)

95 and earlier did not come with O2s after the cat., NEVER any possibly application for sims on them.

7.0 camaro

does anyone here tune without the o2's. i was thinking about it because my engine has slightly higher compression and im running nitrous and would like to run race fuel when i spray. but the race fuel kills o2's right? so what do people do in that case.

96capricemgr

iTrader: (1)

lead kills O2s but does so fairly slowly. If you run race fuel for just the enrichment they would last quite a while.

RamAir95TA

iTrader: (2)

You can't effectively tune a MAF car without the O2s (you don't mention what kind of engine/car/etc. you have). Your O2s will only survive 50 hours of exposure to leaded race fuel - they won't die instantly.

High compression and nitrous? How high are we talking? What else do you have done to need race fuel?

Lots more info needed.

7.0 camaro

i dont know the exact compresion but it does have flat top pistons and the heads have been milled. im guessing at least 11:1. its a 94 lt1. 306 cam. i have a 150 shot on it now and it spark knocked bad. so i put a 685 box on it with 8 deg pulled out when the nitrous is on. i would think if i had some race fuel it would help with that. or just turn down my timing but that kills power.