WhiteDiamond

There are a couple issues with your set up I would address and see if things change. First off, I believe that the single cat idea is a bad one and the cat is most likely way too far back to be of any use. This is coupled to the fact you have the AIR system restricted, providing less oxygen for the cat to use in its conversion of hydro-carbons(needs to oxygen to sustain the burning).

I used 3" in/out CarSound cats on my MTI Stage II heads/B1 cam and passed the IM240 test(sounds like what you are facing) and a standard idle/2500rpm test. The trick was to keep the cats as close to the exhaust ports as possible. I had ceramic coated MACs with a 3" collector mod. Those dumped into a short piece of 3" pipe(enough to get the exhaust under the fire wall and headed correctly under the floor pan) that dumped directly into each of the CarSound cats.

Todd

flyin red TA

LS1derfull,

I have a 100% stock maf that I normally drive around with. I switched to my ported one earlier today to see if that would help lean the car out. Guess the plan didn't work. A ported maf really causes high HC? I thought it would be the other way around. I'm using the LS1 scanmaster which really isn't all that helpful. Gotta find someone with a-tap that can help me out. I thought if I had a lot of misfires, I would set the misfire code?

Does weather have anything to do with it? It was 20 degrees in Chicago today. I have until May to pass again, so I think I'll go on a warmer day.

I think I'm going to get a mac-y with cats to be sure that I can pass. I'm worried that I'll spend a lot of money trying to fix the little things, and that I still won't pass the test. 3 cats will have to make it work. Next time I think I'll even pull out my AIR restrictors too.

Topfuel,

They never even opened the hood or looked at anything. A friend with an LT1 went a year ago wiht no cats at all, and passed the visual and scan tests. He went for the hell of it just so he could get an extension.

Thanks for the replies everyone.

Jim

Hp Joe

You need two cats in your why pipe. they whole point of those is to burn unused fuel.You failed that part part of the test too. So put two cats in your Y-pipe. IF you have them two far back they will not heat up right and if they dont heat up they dont work.

Superman

[quote]Originally posted by Pro Stock John:
<strong>

Anyway, I don't really understand emissions tests, maybe someone could explain it a little.


[ January 17, 2002: Message edited by: Pro Stock John ]</strong><hr></blockquote>
Me neither, I went yeasterday with my work van and it was easier than before they changed all the stations to the dyno deal.
Van was too heavy so no dyno test, stayed in the car, didn`t even rev the engine, I was out in 5 minutes.... had I known I wouldn`t have bothered to disconnect the battery to clear the SES.. i hate resetting radio stations..

Good luck.. I`d get some fake receipts ..

Pro Stock John

iTrader: (34)

[quote]Originally posted by BLK 98WS6:
<strong>There are a couple issues with your set up I would address and see if things change. First off, I believe that the single cat idea is a bad one and the cat is most likely way too far back to be of any use. This is coupled to the fact you have the AIR system restricted, providing less oxygen for the cat to use in its conversion of hydro-carbons(needs to oxygen to sustain the burning).

I used 3" in/out CarSound cats on my MTI Stage II heads/B1 cam and passed the IM240 test(sounds like what you are facing) and a standard idle/2500rpm test. The trick was to keep the cats as close to the exhaust ports as possible. I had ceramic coated MACs with a 3" collector mod. Those dumped into a short piece of 3" pipe(enough to get the exhaust under the fire wall and headed correctly under the floor pan) that dumped directly into each of the CarSound cats.
Todd</strong><hr></blockquote>

I disagree. Jim's setup will take longer to light off the cat but the cat does not need to be right up against the header to work. Can you show me evidence why? OBDI LT1 cars are set up like Jim's car.

My friend's 95 LT1 A4 with a hotcam and single cat passed emissions. I think that Jim has another problem.

I'm all wet if 98's have a much tighter standard to meet though.

[ January 18, 2002: Message edited by: Pro Stock John ]</p>

Holes02

ProStock, the first thing I noticed was your friends car being OBDI.
When did GM switch from OBDI to OBDII ?
Also, when did they give LT1 cars 2 cats?

If it's the same year, then you would have the answer...
I figured that the cat in Jim's car was placed too far back (where the resonator is on a Loudmouth exhaust system) in order to properly heatup and burnoff any unwanted gases.

BIGBOS

I think 96 was the first year...it was either 96 or 97

2000LS1Z28

[quote]Originally posted by BIGBOS:
<strong>I think 96 was the first year...it was either 96 or 97</strong><hr></blockquote>

In 96 the LT1's went to the dual-cat set-up which was the reason for the 10hp jump up to 285 out of the factory although some 95 LT1's also got the dual-cat set-up in the California area(but I have no idea why?).

Jim, so when did you get rid of the Random Tech I sold you? I thought you couldn't stand the way the LM sounded?

Good luck with your 98 T/A.

Mike <img src="graemlins/camaro.gif" border="0" alt="[Chevrolet]" />

LS1derfull

PSJ, you and i seem to agree on this one, but what everybody seems to be missing here is Jims motor is stock, factory doesnt set up a engine design that would run dirty enough to totally count on cats and their placement to pass emissions. THis wont happen, JIM to answer your question, your maf is probably causing your leanness, and it sounds like the only thing you changed that would cause this.Why do you think you need to try and lean stock motor by putting on after market Maf? YOUR exh. mods could be contributing to leanness wit stock calibrations.

LS1derfull

PSJ, you and i seem to agree on this one, but what everybody seems to be missing here is Jims motor is stock, factory doesnt set up a engine design that would run dirty enough to totally count on cats and their placement to pass emissions. THis wont happen, JIM to answer your question, your maf is probably causing your leanness, and it sounds like the only thing you changed that would cause this.Why do you think you need to try and lean stock motor by putting on after market Maf? YOUR exh. mods could be contributing to leanness wit stock calibrations.

LS1derfull

Sorry about 2 of the same replys.
I think people should know that strict emission testing that manufacturers have to get cars to pass is what dictates there component and tuning set ups, what we as customers have to be tested and pass is a whole different animal. Thankfully its alot easier to pass IM240. THIS difference allows for some creativity on our parts to mess with parts and power output. My point to this is the two cats as close to exhaust ports as possible is for just the reasons i explained, GM cant have cold emissions over a certain level, so cats on y pipe fire off that much sooner,IM240 doesnt demand this , GET IT?

Pro Stock John

iTrader: (34)

The thing that some folks aren't grasping, is there are two issues.

Cold start emissions and hot emissions.

Jim's car was was HOT. It should have passed. I know of cars without cats that have almost passed.

With a single cat placed farther back, his cat will probably take longer to light up. BUT IT WILL still light up.

It's like the old codes I got with the G'hann headers and cats. Because the the headers are not double walled like factory manifolds, they take longer to light up the cats since they don't retain as much heat. So pcm would set an SES light because the "catalyst system was below threshhold efficiency."

As a matter of fact, I would bet that a 02 LS1 runs cleaner than a 93Z28.

[ January 18, 2002: Message edited by: Pro Stock John ]</p>

LS1derfull

PSJ, the reality of that situation is the lack of back pressure from no cats could disturb stock calibrations and cause slight miss fire that people would blame no cats for HC increase when its not. CATS are nice to cover up non emission friendly mods like cam.

LS1derfull

PSJ, i agree but you lost me on ls1 vs. 93 Z?

Pro Stock John

iTrader: (34)

I'm saying the LS1 runs cleaner than the LT1.

LS1derfull

I dont think there is one thing about LS1 that isnt more efficient than LT1, thats why i dont think there is any question about that.

flyin red TA

I'm thinking the single cat LT1s had different standards.

New plan is to get a mac y with the regular mac cats. Stock maf, new wires, and new plugs.

LS1derfull...is there a possibility that it still might not pass?

If it still doesn't pass, I can get some receipts to total $450 and I'll just get the waiver.

Thanks again for the help everybody. You have no idea how frustrating this is.

Jim

Mark IXZD 150

iTrader: (1)

[quote]Originally posted by JimTA:
<strong>

Thanks again for the help everybody. You have no idea how frustrating this is.

Jim</strong><hr></blockquote>

Oh yes I do!

Try getting a 1985 Buick Riviera to pass. Sheeesh! <img src="images/icons/rolleyes.gif" border="0">

LS1derfull

JIM, if you do those things you should pass.I want to make sure you understand what i was saying about aftermarket MAF, it doesnt cause HI HC's unless it causes leanness, that leanness can cause missfires with stock programming, and missfires raise level of HC. So dont use it when testing,suspect plugs and wires chage if needed,I dont think your cat and setup is the problem but change it if you want that will only help.