fiercemind

I recently purchased a 98 z28 94000 miles from a friend of mine who i think meant well, but did harm. He has a loudmouth exaust system mounted on, and the catylitic converters are gutted. If I wish to pass any inspection at all, seeing as how I live on a military installation, I need new cats. I am extremely new to anything car related, so I thought I'd make this a project car. Someone give me some insight as to "what key things to check, and what to do as far as a new Y-pipe and cats etc and kinds are best to handle engine upgrades etc. I know I sound new, so bear with me!

teke184

first you need to tell us what kind of inspection you have to pass.

visual to see if you have ANY cats?
visual to see if they are STOCK cats and locations?
sniff test at the tail pipes?
all of the above?

fiercemind

well the thing is, the cats are "gutted" guess that means there's nothing in them so there is more o2 flow? not sure completely but this i guess causes the o2 sensors to read wrong and made the Check Engine light come on and they investigated it. Knocked on the cats and they were empty. It's a North Carolina state inspection, a mandatory bulls****.

teke184

its not that they flow more 02

if you gut the cats and don't reprogram the computer or put in o2 simulators on the rear sensors then you will throw a code.
the code has nothing to do with the running condition of the engine.

the FRONT o2 sensors are the ones used to monitor air/fuel.

get some o2 simulators or a hand held programmer to delete the codes...and the light will go off. then try another inspector.

fiercemind

but in condition with the car, you think it'd be better to just buy new cats? like in the long run for condition of the engine etc?

jmmullin

I don't think cats would have any effect on the engine's lifespan. I'm in North Carolina too and did a heads/cam/exhaust swap and have longtubes (eBay) with high-flow cats (eBay) and Magnaflow mufflers (eBay) in a custom x-pipe true dual setup dumped at the axle; everything total cost about $800, half of it being the fabrication of custom true duals from a local shop.

I haven't GOTTEN it inspected yet, its still about 6 months away, but I did a lot of research with a few shops in the area to see if the setup would meet standards to pass; oh yea I had the codes deleted that set off the Service Engine Soon light, like the O2 sensor code and I guess there were a couple others...That came with my tune after the swap... I'd recommend a good set of high flow catalytic converters, don't gut them, it doesn't make a HUUUGE difference. If you look around you can get a set of two of them for under $100..

Your O2 sensors are reading correctly, but its just throwing the codes, which is "illegal" if not dealt with appropriately From what I know, the only thing keeping you from passing an inspection would be that light being on, so take it to a tuner and get them to delete the codes for $50 and save the money from buying new cats and keep that extra small bump in power from having the current ones gutted.

You said you're on a military installation, would it be by chance Seymour Johnson AFB?

jmmullin

What kinds of engine upgrades were you planning on? A great upgrade in itself is longtube headers... is that included on the car already with a loudmouth system? I don't know if that would mean he put a full system on or not...

The best you can do for exhaust is the longtubes and an x-pipe, some argue an h-pipe is better, but differences are minimal I'd assume; match that up with high flow mufflers and cats if you do end up replacing them and it will be freefreefree flowing

fiercemind

I was on Camp Lejeune, but now I'm on Cherry Point

If I wanted to "legalize" my car, what are some required parts I would need then? Like if I were to get catylitic converters, then I would need a new exhaust system and pipes? what are some good brands that are reliable and upgrades from stock?

jmmullin

It really depends on what is on the car now; you said it has a loudmouth exhaust system mounted on it...do you mean it only has the muffler, or does it have the muffler and pipes through to the back, as in a catback system, or does it have a full loudmouth exhaust from SLP, with longtubes and the catback? Take a look at the pipes in front of and behind the cats. If you can't even see any pipes in front of the cats, and if you look into the engine bay and see some really rusted out manifolds coming out of the heads, its probably still got the stock "shorty" manifold headers on it. If you can see pipes in front of the cats, it has some sort of mid length or longtube headers. The stock piping in front of the cats is very restrictive and is more elliptical in shape than circular.

If he has a catback Loudmouth system on it, the only thing I'd do is longtube headers, which would require a new set of cats. I have Pacesetter longtubes on mine, with a 3" collector, so I run 3" high flow cats, then the rest of the system is also 3". A good upgrade for your car would be longtubes. If you don't plan on any head/cam swap work then 2.5" collectors, cats, intermediate piping, mufflers and tips would be plenty free flowing. If you're going to do major engine work like teke and I have both done, 3" would be a better route. 2.5" piping would also be cheaper to have fabricated, and installed.

We really need to know what all is on the car right now to be able to suggest what you could use. To get the car to be able to pass, you don't need cats, just a tune to get rid of the code from the O2 sensor that is tripping the SES light. To actually LEGALIZE the car yes you need new cats, but nobody could tell the difference nor would they care if your cats are gutted, so long as that light isn't on. You'd save money by going to someone to tune the code out, over what you'd spend on the set of cats, shipping, and installation.

2001NBMZ28

Isn't NC just OBDII plug in now? Is the SES light on? If not, maybe the codes are already turned off or has 02 sims in place of the rear 02 sensors already. New cats are expensive.

jmmullin

Yea, I believe it is only OBDII plug in, but a couple of the shops I went to said they do a visual check to make sure there are cats on the car; they dont see if theyre gutted and don't care if they aren't stock or in stock locations, and they've never failed anyone for cats they said...I think he is saying his SES light is on, so that is all that is holding him back from passing inspection it seems... But I disagree with cats being expensive...I got a set of two hi-flow ones off eBay for $60 shipping included, then had to have them welded in of course so that added on...

fiercemind

well an update from last post guys, this weekend my buddy took me down like a couple hours away, and they did a re-inspection for me and just passed it in the system and gave me a sticker. the light is still on though. Also, is there somewhere that i can get a list of parts that come on the z28 stock? I can't seem to anywhere.

AL SS590 M6

Only thing that I can think of would be to buy a Helms factory service manual.