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What are the pros and cons of going without a catalytic converter

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Old 02-17-2017, 08:11 AM   #11
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Removing CATs? Is that why when I'm behind a rednecks junker, my eyes start watering, and my throat is irritated? Not to mention the stench.
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Old 02-17-2017, 09:53 AM   #12
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You wont need a Tuner or Emulators.
You don't have rear 02's to worry about.
I didn't see the truck in his profile name. Would have been better to note it in the original post. Good catch and note.

Most things still stand though. Increase in sound and especially power will be limited.

Personally I don't think it is worth the time and effort but to each his own
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Old 02-17-2017, 11:36 AM   #13
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Quote:
Originally Posted by Gene K
Do they test 28 yo vehicles? It's not even OBD2.
OBDII vehicles get a computer scan at inspection. Vehicles prior to obdii, but after "classic" status, get a sniffer test. I'm not sure the time frame for "classic", but I think it could be 20 years. Everything else gets a "visual".

EDIT: I need to clarify, that is in Texas, in counties that require emissions testing (I live in Harris county, and we're required to get emissions testing at inspection). Neighboring counties only do safety and "visual" inspection.

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Old 02-17-2017, 12:30 PM   #14
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I realize it's apples to oranges. But on my Mustang GT, removing the cats made it MUCH louder. I do have a few simple bolt on mods to go along with the cat-less midpipe, but just that alone gave me 40 HP and 50 lbs/ft of torque at the crankshaft, verified by dyno.

On our trucks, the exhaust system is even more restrictive because they aren't building F-150s for enthusiasts, they're building them for fleets and the working man. So in order to kill the noise they have more restriction in the system. Therefore I would assume large gains could be had on the trucks also.
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Old 02-17-2017, 12:32 PM   #15
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Removing them won't gain as much as many think. Power gain is less than 2% on 700 bhp Supercharged Coyotes.


Yea, its not like the old 70's pellet converters where you could pick up 30+hp by taking the pos off.


New high flow cats really do on provide any measureable level of degraded performance.
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Old 02-17-2017, 12:55 PM   #16
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Do they test 28 yo vehicles? It's not even OBD2.

On my '79 Silverado, they shove a probe up its tailpipe and actually measure the gasses, since the standards are different for older vehicles.
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Old 02-17-2017, 01:00 PM   #17
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You wont need a Tuner or Emulators.
You don't have rear 02's to worry about.

That's incorrect. Without being able to read the O2 sensors, an error code of not ready will be thrown and the test will be incomplete. The tester has to be able to read the sensor heater voltage, no sensor, no heater data.
This is why some tuners have to be returned to stock and then driven for a period of time before a test will be successful. Then after the test, return to the tuner.
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Old 02-17-2017, 01:19 PM   #18
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Quote:
Originally Posted by WXman View Post
I realize it's apples to oranges. But on my Mustang GT, removing the cats made it MUCH louder. I do have a few simple bolt on mods to go along with the cat-less midpipe, but just that alone gave me 40 HP and 50 lbs/ft of torque at the crankshaft, verified by dyno.

On our trucks, the exhaust system is even more restrictive because they aren't building F-150s for enthusiasts, they're building them for fleets and the working man. So in order to kill the noise they have more restriction in the system. Therefore I would assume large gains could be had on the trucks also.
I would be highly dubious of this claim.

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Old 02-17-2017, 06:42 PM   #19
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Yes and no. Our vehicles have a 4 stroke engine and are not susceptible to changes in back pressure. Old wives tale. In fact, less back pressure means more power, to a point.
That is not entirely true either. The design of the exhaust can promote reversion which clears out the cylinder and improves cylinder pressures at low rpm improving torque. Opening up the exhaust while improving hi rpm power can, not in all cases, reduce low end torque.

Probably not true in the case of the eco-boost because of the small turbos spinning up quickly.
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Old 02-17-2017, 10:30 PM   #20
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It comes down to, do you REALLY want to challenge the EPA? They don't care who you are, and if caught, well, extreme butt hurt comes to mind. EPA sucks.

https://www.epa.gov/sites/production...hsysrepair.pdf

However, getting caught can induce major butthurt, but you have to get caught, and that is something that for the most part, never happens, unless you happened to p1$$ off an EPA agent.

Frankly, the gains, are not worth it on today's vehicles, you can replace the OEM ones with High flow ones and after market full exhaust, get HP gains and still stay compliant.
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