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Old 02-27-2012, 08:26 PM   #1
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Default Bypassing emissions?

I don't own an F body yet but plan on getting a Trans Am when I actually need a DD (my 1966 pontiac is my weekend warrior right now ). At a car meet with a few F body guys one of them mentioned that you could pass emissions even if you don't have a cat, don't remember exactly how. I think it was something to do with a tune or something little electronic (assuming no tailpipe test)?

When I do look at buying a TA, I'll be limited in price because of my college kid budget, probably around $5000 for an M6. The best deals to be had right now are Florida TA's, but they don't require emissions there. I figure a ton of those cars will fail emissions or have cats removed.

My question is, can you (somewhat easily) "pass" emissions with an LS1 or was this guy just talking out of his ***?
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Old 02-27-2012, 08:42 PM   #2
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Depends no where you live and how strict your emissions testing is (whether they do the sniffer test, visual, etc., etc.). I don't have cats on my Camaro and passed Maryland emissions easily. But they are no different from any other car if you have all the necessary emissions equipment on them.
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Old 02-27-2012, 08:59 PM   #3
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Depends no where you live and how strict your emissions testing is (whether they do the sniffer test, visual, etc., etc.). I don't have cats on my Camaro and passed Maryland emissions easily. But they are no different from any other car if you have all the necessary emissions equipment on them.
They don't do sniffer unless its -96, I'm talking about like a reprogram of the sensors or something. The guy implied you can get around emissions easily, I'm wondering if it's possible without cats on paper if the individual tester looks the other way because of the obvious smell..

Live in Metro Atlanta if anyone has experience here.
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Old 02-28-2012, 12:02 AM   #4
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Passing without cats is a simple matter of custom tuning or O2 simulators plugged into the rear O2 sensor harness. Now, this method will only work if the test in question is an OBD scan only test. If you have a visual or sniff test, there is no way to pass without cats (or at least something that looks like cats, if it's just a visual), unless you have some sort of connection.
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Old 02-28-2012, 08:53 AM   #5
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What state are you in?
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Old 02-28-2012, 02:20 PM   #6
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What state are you in?
Georgia
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Old 02-28-2012, 04:20 PM   #7
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From Georgia's clean air force site:
All 1996 and newer vehicles will receive a three-part inspection:

•An OBD test to check your vehicle’s emission control performance history.
•A fuel cap inspection to check for adequate seal.
•A visual inspection of the catalytic converter to check for tampering or removal.

Looks like you have a visual test.... I do not know how strict that is... but you may have to at least have something that looks like cats.

Now what you heard this person at the meet say about a tune is what RPM said above. You can tune your car via a tuner like HP Tuners and simply delete the codes that trigger from removing cats/other emissions items so that they do not trip the check engine light and you can pass the OBD scan part of the test. The visual though is another story... and again idk how strict your state is. In IL we only have the OBD scan test, and I pass every time with my cars, and none of them have cats.
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Old 03-06-2012, 02:56 PM   #8
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Theoretically, if a TA I bought didn't have a cat and I put two hollowed cats on to pass the visual inspection, would there be any issues with flow? A quick google search comes up with some people worried about flow because the cat is now wider than the exhaust piping.

Legit concern or nothing to worry about?
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Old 03-06-2012, 04:49 PM   #9
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Just run two hi-flow cats. Unless you are making huge power you will never know they are there. The gains for removing them are greatly overrated IMO. I have two 3" Magnaflows and I bet they cost me next to nothing..... I have the Magnaflow 3" 300 cell density ones that flow right at 600 cfm at the top of the graph in this thread>>>>>which cats are which - and which are best?
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Old 03-06-2012, 05:00 PM   #10
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Theoretically, if a TA I bought didn't have a cat and I put two hollowed cats on to pass the visual inspection, would there be any issues with flow? A quick google search comes up with some people worried about flow because the cat is now wider than the exhaust piping.

Legit concern or nothing to worry about?
1) The exhaust is already flowing through that same cat shell prior to gutting it. If the shape of the chamber was a problem, then it was already a problem before gutting the cat. In other words, I don't see how removing the material (which, in effect, is just a screen, since there are no chambers or baffles inside to direct or contain flow) would make the shell flow any worse.

2) I actually did exactly what you have suggested many years ago, before there was any affordable option for an ORY to bolt to stock manifolds. The car seemed to feel slightly stronger with the cat shells gutted (though I never did any dyno or track testing to prove this), but it certainly didn't feel like it lost any power at all. One nice thing about the gutted shells is that there was ZERO rasp this way (as compared to an ORY with no cat shells). I've seen some people talk about how gutted cats sound raspier than an ORY, but having personally done this myself I'm here to say that these people must never have actually done this to think that way - because it's simply not true. The car sounded fantasic with gutted stock cats and a couple different catbacks.

3) I have seen a website somewhere that sells what looks like a cat, but inside is a pipe that flows straight through. This is perfect for people that have to pass a visual but don't have to pass a sniff. You could either find something like this, or you could actually make it yourself if you have the materials and tools. Just another option if you are really worried about the flow.
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Old 03-06-2012, 05:05 PM   #11
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Just run two hi-flow cats. Unless you are making huge power you will never know they are there. The gains for removing them are greatly overrated IMO. I have two 3" Magnaflows and I bet they cost me next to nothing..... I have the Magnaflow 3" 300 cell density ones that flow right at 600 cfm at the top of the graph in this thread>>>>>which cats are which - and which are best?
It's more than just the performance gains though. That is only part of the equation. It's also cheaper to buy an ORY (or to leave cats off when building true duals), and it creates less complication when running the exhaust (clearance, leaking points, etc.), and you don't ever have to worry about them clogging at any point in the future if you just leave them off.

IMO, if you live in a place where you can get away without them, then I would leave them off when building a custom exhaust. No reason to spend more money for no gains and the additional complications I listed above. Just my opinion.
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Old 03-06-2012, 06:30 PM   #12
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It's more than just the performance gains though. That is only part of the equation. It's also cheaper to buy an ORY (or to leave cats off when building true duals), and it creates less complication when running the exhaust (clearance, leaking points, etc.), and you don't ever have to worry about them clogging at any point in the future if you just leave them off.

IMO, if you live in a place where you can get away without them, then I would leave them off when building a custom exhaust. No reason to spend more money for no gains and the additional complications I listed above. Just my opinion.
That's the thing. I would have to pass a visual emissions test, I don't give a damn if I have cats at all, functional or not. I'm talking cheapest way to pass the friggin emissions, and hollowed cats seem to be just that. Thanks for the input.
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Old 03-06-2012, 06:52 PM   #13
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Originally Posted by RPM WS6 View Post
It's more than just the performance gains though. That is only part of the equation. It's also cheaper to buy an ORY (or to leave cats off when building true duals), and it creates less complication when running the exhaust (clearance, leaking points, etc.), and you don't ever have to worry about them clogging at any point in the future if you just leave them off.

IMO, if you live in a place where you can get away without them, then I would leave them off when building a custom exhaust. No reason to spend more money for no gains and the additional complications I listed above. Just my opinion.
Points taken RPM.. I have a yearly visible inspection and have never been questioned in 4 years and it tones down the exhaust a bit which is still obnoxiously loud through a Hooker cb.
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Old 03-07-2012, 02:38 AM   #14
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Passing without cats is a simple matter of custom tuning or O2 simulators plugged into the rear O2 sensor harness..
im in need of o2 simulators but cant find them anywhere (i guess they're illegal?). anyone know where to get them? my friend has mil eliminators (legal) for his mustang that serve the same purpose but i guess they dont make those for our cars.

o2 simulator - illegal
mil eliminator - legal
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Old 03-07-2012, 05:49 AM   #15
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I passed inspection with deleted EGR, deleted smog pump and no cats...I got a mail order TunebyFrost and no check engine light
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Old 03-07-2012, 11:38 AM   #16
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im in need of o2 simulators but cant find them anywhere (i guess they're illegal?). anyone know where to get them? my friend has mil eliminators (legal) for his mustang that serve the same purpose but i guess they dont make those for our cars.

o2 simulator - illegal
mil eliminator - legal
LT headers, ORYs, anything that relocates or removes the cats, aftermarket cams, etc....are all illegal for use on the street, as is anything else that increases emissions beyond the factory level.

You can still get O2 sims from Speed Inc, right here in IL (scroll down to almost the bottom of the page):

http://www.speedinc.com/catagory.cfm?catagory=Exhaust

You can also find them used from time to time.

Or, you could just get a custom tune to delete the rear O2s. O2 sims only make sense to buy if you never plan to get a custom tune.
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Old 03-07-2012, 05:10 PM   #17
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O2 sims only make sense to buy if you never plan to get a custom tune.
Thats me. I appreciate the help but cant find o2 sims on the speedinc site
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Old 03-07-2012, 05:51 PM   #18
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Thats me. I appreciate the help but cant find o2 sims on the speedinc site
Sorry, that last link I gave you somehow went stupid. Anyway, here is a revised link:

http://www.speedinc.com/cont.cfm?cid=C0000042

I too have used these on cars that I don't intend to ever get tuned. They've worked great.
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Old 03-07-2012, 09:50 PM   #19
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thank you my friend
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Old 03-07-2012, 10:10 PM   #20
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Thanks for the help!

I have one last question -can a car be tuned by someone who bought a handheld tuner and knows what their doing disable the sensors, or is a "real deal" mail order or dyno tune necessary?
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Old 03-07-2012, 10:10 PM
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