Removing the Cats
Not sure if it will help since you don't have anything else to help your car breathe better. Changing out your headers and h-pipe will definetely free up some nice power and make your ls1 breathe much better. Maybe try a search on the subject and see if you can get some more info on the subject of stcok exhaust without cats. If you do get rid of them you can pick up a pair of 02 rear simulators pretty cheap from afterthoughts auto. Taking off the cats can draw attention to you so be aware and make sure your in an area where cops won't bother you. Fines for not having them can be quite steep. Hope this helps out some.
I went with the Bassani Off Road Y-pipe, it was a few years ago, but I think I paid about $220 shipped. Bolted right up in 1.5 hours, you will need the two O2 sims for rears. It looks like from your mph your Z has M6 also, you might gain a couple mph. I did mine the same time as underdrive pully so hard to tell what gain. With both mods I went from consistant 12.7s to 12.5s.
If you plan on doing more internal mods in future go with long tubes w/ ory.
If you plan on doing more internal mods in future go with long tubes w/ ory.
I have stock manifolds and y-pipe with an SLP LM catback. I'm putting on gutted cats so I still need the two rear O2 sims, right? I hope because I just ordered them. Thanks!
Pros - More sound and a FEW ponies
cons - Exhaust smell is strong untill you get the car tuned (even then you will still smell it), Cost of o2 sims/get the o2 tuned out, possibility of a fine
I would get them removed only if you plan on doing headers, I am doing headers and not putting any cats in but I have a diablo sport to tune them out too.
cons - Exhaust smell is strong untill you get the car tuned (even then you will still smell it), Cost of o2 sims/get the o2 tuned out, possibility of a fine
I would get them removed only if you plan on doing headers, I am doing headers and not putting any cats in but I have a diablo sport to tune them out too.
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TECH Resident
Joined: Aug 2003
Posts: 970
Likes: 4
From: England UK
Originally Posted by Marblehead
I didn't realize that I would have to tune it. Won't the sims take care of that? Is it gonna run like ****, rich or lean at WOT until it's tuned? Damn tuning is expensive!
You car will run fine with cutted cats and O2 sims. Not rich or lean the fuel trims will tune it for you. Also WOT wont be any further off than before you cutted the cats, well not much off, you car may breath a little better, but not much change.
TECH Resident
Joined: Aug 2003
Posts: 970
Likes: 4
From: England UK
Originally Posted by Marblehead
Thanks!! The O2 sims were $34 each. I really appreciate the quick response!!
I thought they were talking about tuning with LS1 Edit. Thanks again.
I thought they were talking about tuning with LS1 Edit. Thanks again.
My friend has a dyno shop and does tuning, which I'll do as needed. I'm just looking for a few extra ponies with the gutted cats. I'll dyno the car with the gutted cats and then I'll know exactly what the gains are, if any are of gutted cats. 
rear o2 sensors Rear O2 sensors are only used to check operation of the cats.
Rear O2 sensors are really a emission check. they read the O2 ppm after the cats... check the efficency, so when you put in rear sims they only thing your doing is tricking your ecm into thinking the cats are working properly.
Long tube headers will increase horsepower with a matched y pipe helps the engine breath.
now just stock manifolds with a y-pipe will do very little in hp numbers,
waste of money to buy sims and y-pipe with no long tube headers.
just my 2 cents.
Rear O2 sensors are really a emission check. they read the O2 ppm after the cats... check the efficency, so when you put in rear sims they only thing your doing is tricking your ecm into thinking the cats are working properly.
Long tube headers will increase horsepower with a matched y pipe helps the engine breath.
now just stock manifolds with a y-pipe will do very little in hp numbers,
waste of money to buy sims and y-pipe with no long tube headers.
just my 2 cents.
gutting the cats really wont do anything except make you car a little louder, and make it stink. if you had an ORY you may see minimal gains. But because of the turbulence caused by the cat being not a smooth internal surface and a diff size and shape you wont see any gains
It was worthwhile for me to get an off-road Y when the long tube headers were installed. The primary factor for me was the change it made to the exhaust note and the small performance gain was of secondary performance. At the end of the day, it works out for me perfectly because my car still sounds SOMEWHAT civilized on the highway, however just pop open the cutout and it goes to NASTY pretty quickly.
Originally Posted by Marblehead
Thanks!! The O2 sims were $34 each. I really appreciate the quick response!!
I thought they were talking about tuning with LS1 Edit. Thanks again.
I thought they were talking about tuning with LS1 Edit. Thanks again.