sc1 CATS and O2's

[krimson]

Alright, heres a common mod I've done w/previously owned cars. When 1 O2 sensor is present pre-cat converter, you can hollow or remove your cat, but on this 2001 sc1 there are 2 o2 sensors and 2 cat converters. Working down the exhaust stream now: exhaust manifold has a built-in cat w/ 02 sensor before the cat, further down the line (of course) another cat and o2 sensor after it.
Is the 1st cat a Cali emissions thing, and can it be hollowed without throwing a code or the use of an O2 Simulator? Thanx

[97sleeper]

Yes, the 1st cat is a Cali emissions deal, you can hollow it out but as a warning it may set a code off because of it though. I'm not 100% sure on that but I'm sure someone will chime in to add.

[Firehawk_1989]

I'm not sure what you mean buy 2 cats, one being in the exhaust manifold. (could you get a picture maybe?) But, you can not hollow out your cat without setting a code, caused by the downstream 02 sensor. Just leave your cat how it is, and replace if needed. You won't see any real noticable gain from gutting it, besides a nice little light in your dash, telling you you messed it up. And I would never use an 02 simultor. but thats just me. hope this helps you out! :-)

[Firehawk_1989]

ah, well as 97 sleeper confirmed, its a cali thing, thats why i have not seen it. you will most likely set a code though.

[krimson]

Thanxs for the info guys. What I am gonna do though is soon acquire a used manifold from a yard or elsewhere for little to nothing and hollow that one and test.

[madpogue]

Or look for a non-CA manifold.

[97sleeper]

Originally Posted by Firehawk_1989

ah, well as 97 sleeper confirmed, its a cali thing, thats why i have not seen it. you will most likely set a code though.

Yea, Cali wasn't the only place that they sold the Cali emissions set up cars but it is what the set up is named after. I just think they didn't sell many outside of Cali, thats all.

[cloud819]

My 2001 SC2 had a precat and deleting it did nothing to codes. Mine went bye bye because of a header install.

I wouldn't do it unless the thing is clogged. It isn't really worth anything on a SOHC, thety doesn't breath. If you need to do it because it is clogged, cool. But it isn't worth the time performance wise.

[krimson]

So, Cloud 819, bottom line what you're saying is, if I knock out the pre-cat biscuit in the manifold it will not throw a code? As far as the SC1 not able to breath I have to beg to differ. I fully ported polished and matched from the air entry (all sharp edges smooth and polished), to throttle body (bored and and port matched), to intake manifold (port matched), to exhaust(ported and polished) and this thing scoots tremendously more than stock. All I want to do is free up a little more back-pressure, not alot. So honestly now, If I do that, it will not throw a code? thanx

[cloud819]

Originally Posted by krimson

So, Cloud 819, bottom line what you're saying is, if I knock out the pre-cat biscuit in the manifold it will not throw a code? As far as the SC1 not able to breath I have to beg to differ. I fully ported polished and matched from the air entry (all sharp edges smooth and polished), to throttle body (bored and and port matched), to intake manifold (port matched), to exhaust(ported and polished) and this thing scoots tremendously more than stock. All I want to do is free up a little more back-pressure, not alot. So honestly now, If I do that, it will not throw a code? thanx

It shouldn't throw a code.

SOHCs don't breath. A fully port matched SOHC with headers and an intake, won't outflow a stock DOHC. If you are into taking taking apart the top part of the engine, why not slap a DOHC head on it and swap the other things need to make it a DOHC? If I recall the 2000+ SOHC have the same bottomend as the 2000+ DOHCs.

[krimson]

Look. No disrespect intended here, but I thought the whole point of "Tuning" is working with what you've got. I dont have a DOHC and Im not trying to make one. Im working with the SOHC because it was a steal at the time, and taking things apart to make things more efficient is a passion for me. Not many people will put this much effort into something like this SOHC, and Ive spent no money except 35 for an intake and everything else was done by my hands and Ive squeezed out more power, torque and gas mileage out of it. Thats an achievement in my opinion not a waste of time.
Thank you for confirming my question about the O2 codes.

[cloud819]

Originally Posted by krimson

Look. No disrespect intended here, but I thought the whole point of "Tuning" is working with what you've got. I dont have a DOHC and Im not trying to make one. Im working with the SOHC because it was a steal at the time, and taking things apart to make things more efficient is a passion for me. Not many people will put this much effort into something like this SOHC, and Ive spent no money except 35 for an intake and everything else was done by my hands and Ive squeezed out more power, torque and gas mileage out of it. Thats an achievement in my opinion not a waste of time.
Thank you for confirming my question about the O2 codes.

No disrespect taken. I completely understand working with what you have. I think it is really cool to "perfect" a design, no mater how silly the work may seem to others. But you should also realize where the limiting weakness is. You said they can breath.

While you can make them better, you are still limited by the design itself. I doubt a SOHC can out breath a cat in good condition. My lawnmower can out breath a clogged cat. If it is clogged it is robbing you of power, if it is not, then there is no really measureable power to be gained.

[krimson]

Im glad you understand. and I do know that it is a SOHC and its valve-train is very simple. As a matter of fact the first thing I noticed after doing all my so-far work, and did a launch test, is that the engine wanted to keep making power past its pre-determined limits, but the last thing I want is to blow a head. The "band" now, is tuned at peak torque rpm, drops a little, then dramatically increases near redline limits and up. So my whole point of this thread is to maybe tune it to take advantage of the medium power band. I know that decreasing backpressure may not increase HP, but it can release your HP at a different band, hence different types of headers for same engines. Im hoping that having a free collector may achieve some of this. What do you think? thanx