Opacity test numbers without a cat?
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Mountain Pass
Joined: Mar 2009
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Opacity test numbers without a cat?
In AZ (Maricopa County), we have emissions testing. It’s a visual inspection to make sure the cat is installed. There is also an opacity test done. Does gutting the cat alter (raise) the opacity readings?
Lead Driver
Joined: Sep 2002
Posts: 9,500
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From: North Texas
On a stock tune? It will hardly puff at all catless.
They are doing what is also known as a snap test. Basiclly rev it a few times and check smoke output. Now my question is who decides what is acceptable and what is not?
IMO, if you are not pouring smoke out, you are fine.
They are doing what is also known as a snap test. Basiclly rev it a few times and check smoke output. Now my question is who decides what is acceptable and what is not?
IMO, if you are not pouring smoke out, you are fine.
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Mountain Pass
Joined: Mar 2009
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I have a TS 6 position switch, but I’d be sure to switch it to “stock” before an emissions test. The truck doesn’t smoke when driving, but at 1st startup in the morning, it does puff a bit. I’m wondering if one (or more) of my injectors doesn’t have a perfect o-ring. My MPG is pretty good. Around 16 mpg. It’s an Ex Cab 4x4 with 4.10s and 295/75/15 (almost 35”) Hankook MT tires.
More Turbo
Joined: Feb 2010
Posts: 661
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From: parma
96 F250 Powerstroke I just passed my last emission test here in Ohio. Any vehicle over 25yrs old doesn't get tested anymore. That's cause they figure the average of 25yr old vehicles not rusted to death is a minimum. Tailpipe test on mine. Checked for a cat, then ran it on the rollers. They drive it up to 55mph and hold it there. Then the sensors take a reading. Mine passed with flying colors. Just make sure the truck is well warmed up before the test.
Laughing Gas
Joined: Feb 2014
Posts: 774
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From: Reno, Nevada
We have an annual opacity test here also. My biased opinion is that since a cat has some backpressure against the turbo, the turbo spools slower and is less efficient with the cat installed so your vehicle is going to get less air flow to the combustion chamber and is likely to score worse on the opacity test with a stock cat than with a gutted cat.
Lead Driver
Joined: Sep 2002
Posts: 9,500
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From: North Texas
All the engine killing smog crap fell off my 6.4 when offroading once. I never had a problem in Texas with a visual portion...which is required by law. They gave me the OBD2 test and away I went.
Chances of some kid knowing these early 7.3s had a cat are slim to none. If that worried, just do what we have done for years...gut it, reinstall shell.
Chances of some kid knowing these early 7.3s had a cat are slim to none. If that worried, just do what we have done for years...gut it, reinstall shell.
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pullnit
1999 - 2003 7.3L Power Stroke Diesel
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Feb 1, 2005 02:55 AM
