Air Care 2003 GT

Your car has cats but they are high flow which is why your light is on. The high flow cats work just as well as the stock cats, they just flow more air. As long as everything else is in proper working order you should be fine as far as emissions is concerned. The MIL eliminators will prevent the computer from detecting the extra exhaust flow so it won't trip the check engine light. The rear O2s will still operate and they can still communicate so everything will be fine when they plug the scanner to you OBD2 port. You should have no problems with the MIL eliminators.

On the other hand I have been tuning my Mark VIII with Sniper as an alternative to using MIL elims. Yet, when I took my car to DMV here in NJ I failed because their computers said my ECU was not in readiness mode. This was after 500 miles driving with the tune. They were able to read the ECU 60 miles after I returned the car to stock tho. The tech there said they upgraded their software so now you will fail if there is a tune installed in your ECU regardless of how many miles you drive...even if the CEL is not on. The tune somehow interferes with the communication from the ECU to their scanners. Just a heads up for you guys out there...

Hi flow cats don't work any near as well as factory cats. First, the fact that they flow more means they have less surface area for the catalytic reaction to occur. Second, most aftermarket midpipes only have two cats located down under the floor. The OE midpipe on a 2003 had 4 cats, two right up by the manifolds and two under the floor, each doing a specific job.

If the MIL is on it means the cats are not dealing effectively with unburnt HCs. The exhaust content coming out of the cats is not far off what it is going in. That's what the rear O2 sensors are there for, to monitor catalyst efficiency, not total exhaust flow. The front O2 sensors are used for fuel feedback. Their signal swings between 0.2V and 1V (give or take) as the mixture is adjust lean and rich, respectively. In contrast, the sensors on the output side of the catalytic converter should be producing a much smoother output, varying little if the cats are doing their job because the chemistry of the exhaust gas is much more consistent. In fact, this is what MILs do: They are simply an electrical low-pass filter for the rear O2 sensors that smooth the output voltage fooling the PCM into thinking the cats are fine.

If the cats are inefficient in terms of the catalytic reactions, MILs might help get rid of the MIL but they won't help you pass an IM240 rolling-road test. It's one thing to fool the PCM with a LPF on the rear O2 sensors but you can't change the exhaust chemistry with a MIL eliminator. For that you need a decent cat.

AirCare claims to do "tampering inspections". They may be satisfied to see cats there though I don't know if they will know they aren't factory cats. If they don't do an OBD-II readiness check, you can erase the codes in the parking lot of the inspection station and try the test. If the exhaust quality is bad enough to make the rear O2s unhappy I doubt you'll pass though.

If you fail, you're going to need to source better cats or perhaps a stock midpipe: Bolt it on, test it, then put your high-flow setup on afterward. I went through this with my MRT catted-H and finally had enough and just left the stock midpipe on. Just went for DriveClean (Ontario's version of AirCare) and the car was cleaner than it was 7 years ago...

My Mustang actually had 6 cats from the factory believe it or not. I did a Pypes exhaust system with 2 high flow cats and ran MIL eliminators. I was sweating bullets at DMV but I got through the sniffer no problem. I don't know the differences in other states or in Canada but I got through ok. They looked under the car and saw the exhaust and the cats but they failed to check that my mileage was only 22,000 at the time which would have meant a rejection sticker for me because you can't change your cats with anything other than OE for the first 50,000 miles (so I've been told at inspection). My car still doesn't have 50,000 miles and that was 4 years ago. Got away with it so far.

They don't use a gas analyzer in BC on OBD II vehicles 98 and later. They scan the car and if there are any codes or all the readiness monitors haven't run then you'll fail. It's just easiest to throw the stock cats back on, clear the codes and drive it for a few days, then have it tested. That's what I do.
If you have a tune that turns the o2 sensors off the readiness monitor for that cat efficiency test won't run and you will fail. Aftermarket high flow cats do not generally work well enough to pass the cat efficiency test.

ohsnap:

Your car should pass just fine. The MIL eliminators tell the computer that the cats are working (warm) even if there are no cats. The readiness monitor just checks that the rear O2's are working (or, the signal from the MIL eliminator is making things look like they are working) after a driving cycle is complete.

Be aware that the evap system takes a long time to run through and complete. It needs warm-ish ambient temperatures and a few cold starts. It is the one system that might not be ready. However, most tests allow one 'not ready' loop, depending on the year of the car.

If you have a little extra cash, you can buy the CarCode monitoring program that runs on your laptop. It is primarily an emissions test checker but it also allows some decent datalogging. It is very comprehensive, well supported, and not expensive. Check out "obd-2.com" for more details. FWIW, I run it now and then (especially as test time approaches) just to make sure everything is running well.

HTH,

Chris

Three50won said:

Your car has cats but they are high flow which is why your light is on.

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I've got a catted Bassani midpipe and I've never thrown a CEL code. Depends how finicky your computer is. Most who go catted never throw a code, but afew do and get the MILS. If your car had 6 cats was it a 2004?

I have MIL Simulators on my car, not Eliminators, for about 2 1/2 years now and has worked like a charm. I have shorties, offroad X and welded 2 chamber flowmasters.

03machone said:

I have MIL Simulators on my car, not Eliminators, for about 2 1/2 years now and has worked like a charm. I have shorties, offroad X and welded 2 chamber flowmasters.

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03machone:

Interesting. Not having used them, I thought there were only MIL eliminators. Do the simulators generate a variable signal or just a constant signal so that the PCM thinks that cats are installed. Also, for the benefit of the guys who need these little gems, where did you get yours, please?

Thanks,

Chris

Forgive me for my typagraphical error i meant O2 Simulator.... same darn thing. The guy that does my e.t says that when sims are used they keep the computer thinking its in optimal running frequency. When they are shut off or eliminated they close that functioning history down and when they run the test they don't pull up continious data therefore fail it. I got mine from O2simulator.com........ If going this route please take care in water proofing the controller to avoid problems.




P.s I just realized you are from chesterfield, I am right out in O'fallon MO.

If you bought them you might as well try.... I don't know if its different up there, but if they tell you the same thing and it doesn't work you will know how to fix it.

You need to find out from some of your neighbors what the typical vehicle inspection is like.

With MIL Eliminators/O2 simulators you should pass a OBDII scan test no problem but you may fail a visual inspection if they notice them or if they see you've only got 2 cats and their database says a 2003 GT should have 4 cats. It just depends on what they how far their inspections go up there.

ohsnap said:

Is it this one? Universal o2 simulator dual output [unv-o2sim2] - $40.00 : O2 Simulator, E-commerce

It's the universal one? It's dual right? Not single?

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Yep thats the one.