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Legality of replacing a working catalytic converter with a better one

With the price of gasoline on the rise, I was thinking about one or two upgrades that might help improve the mileage of an old 1998 acura. I really want to upgrade the factory exhaust system to help the engine breath easier. replacing the factory manifold with headers is an easy choice, but I’m wondering about the catalytic converter and the EPA’s rules. If the cat is still in working condition, even though it’s closing in on 20 years old, am I allowed to replace it with a more modern one with less restriction if the emissions stay the same or get better? It’s a question of spirit of the law vs. letter of the law.

No is the legal answer. ( this is my opinion only and I am not a lawyer.) The practical answer is probably only if you live in a state with no emissions testing.

I saw a really funny episode of Peoples Court where one of the litigants had a foreign accent and could not pronounce lawyer and liar differently.

Calculate the payoff, then decide, Loosing proposition in my book.

How can it be not legal? What do you do if your cat needs replacing, get a new one, right?

Because he doesn’t want to replace it with a LIKE KIND converter; he wants to upgrade.

From what I know, the EPA is anal about such things. You either get the correct serial number part, or a part that has been “determined to be equivalent” (by MFR spending for testing)…or you’re “noncompliant.” The fact that the converter you’ve installed may well be far more efficient/less polluting than OEM is beside the point!

Another instance of EPA inflexibility: with “modern” lawnmowers, the carb adjustments are set at the factory, and plugged with tamper-proof seals. If I happened to notice it was running far too rich on “default” settings…and I defeated the seal to lean it out…I’d have a cleaner-running mower that consumed less gas, AND I’d be in violation of the Clean Air Act.

Replacing a “vehicle-certified” part for an “uncertified” part is viewed as “tampering,” regardless of whether emissions stay the same, go up…or even go down.

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I think you are wrong. Here is a link to the EPA rules regarding aftermarket cats:\zyfiles\Index%20Data\86thru90\Txt\00000030\9101NNNC.txt&User=ANONYMOUS&Password=anonymous&SortMethod=h|-&MaximumDocuments=1&FuzzyDegree=0&ImageQuality=r75g8/r75g8/x150y150g16/i425&Display=hpfr&DefSeekPage=x&SearchBack=ZyActionL&Back=ZyActionS&BackDesc=Results%20page&MaximumPages=1&ZyEntry=1&SeekPage=x&ZyPURL

I get this:

"ZyNET error: Named file not found in this branch of the Table of Contents
A report of this error will be forwarded to NEPIS technical staff for evaluation. "

And that’s from what, 1989? A lot of CFR has been written between then and now. I DO know that “California emissions” (which have federal effect, which is how CA get around the whole “Commerce Clause” issue W/R/T interstate trucking) WILL NOT allow you to run ANYTHING that doesn’t have the right EO digits. It could be made out of Vibranium; it could cause polar bears to dance a jig of happiness; it’s “no can do” if the number’s don’t match.

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don’t know why the link does not work for you. I can click on it and it works fine. Try copy and past.

Aftermarket cats, as long as they are used as the manufacturer specifies, are fine. In other words, if the cat says for 3 liter engines, single exhaust, or smaller, you are fine. If California takes offense at this, also fine. You choose to live there, you live by their rules.

Aftermarket cats sold there must have a CARB EO number which, of course, costs the manufacturer to certify, to use on a given car. California legal cats cost you more because of this government twaddle but so does everything else in that state.

That said, modern cats flow quite well as do most modern exhausts. Long gone are the days where headers would get you a 30 percent power boost. You might get 10% if you are lucky and the mileage likely won’t change even that much. Simply buying low rolling resistance tires would save you as much or more and cost less.

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Don’t expect a more freely flowing exhaust to make a noticeable difference in gas mileage. The biggest impediment to airflow though your engine is still going to be the nearly closed throttle that controls airflow through your engine in order to control the power output.
The only way that a free flowing exhaust gives you a gas mileage gain is if the noise encourages you to drive slower in order to avoid a noise ticket.

The only place a free flowing exhaust makes a difference is at full throttle and high rpm. At low rpm, there is not enough flow to create a significant back pressure and at part throttle, it’s the throttle, not the exhaust or air cleaner that is the air flow bottleneck.

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+1 to everything that B.L.E. stated.

Additionally, I have to wonder just how many miles the OP drives annually, and how much longer he expects this car to last, in order to justify spending significant money on an alteration that will yield–at best–only a very meager increase in MPGs.

Putting on headers is illegal as far as the EPA goes unless they’ve been approved. Most haven’t.

Why someone would even think about spending the amount of money it would take for an exhaust system which might not even give better fuel mileage is beyond me. And a 1998 vehicle also.

That’s why you’ll see the words “for off road use only” on a lot of aftermarket exhaust systems.

Forget about the legality; replacing a working cat is a waste of money; you will not get better performance.

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A few cities have been charging the riders of loud motorcycles with illegal tampering instead of excessive noise. The reason is because tampering is so much easier to prove.

I don’t agree with headers being illegal per the EPA and neither do the guys who sell them.

and these guys, too;

There are a lot of vendors for headers. And there are 50 state legal, CARB E.O. certified long tube headers.

Here is one by JBA

Even if they are legal, I cannot figure out how the OP believes that he will “save money” in the long run by installing new exhaust components and a new catalytic converter on a car that is almost 20 years old.

I don’t think that I could afford to save money that way.

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Have you done a compression check on your 1998?
Do you have an engine analyzer?
The best way you can ensure your best mileage on a car this old is as good as possible is to ensure that the compression and the ignition system are in good shape and operating properly. Repair anything you find that is no longer operating like new. But, if the compression is low or uneven, just be sure the ignition system is operating properly and enjoy the car as long as you can.

At the time your car was designed, manufacturers were deep into designing for fuel efficiency. The federal Corporate Average Fuel Efficiency standards were adopted in 1975, many years before your car was designed. And emissions mandates began even earlier, in 1970. Engineers were deeply steeped in the quest for better gas mileage by 1998.

“Upgrades” are often not what they’re advertised to be, marketing types are ingenious at lying. One to be avoided at all cost is Cold Air Induction (CAI) systems. These have been known to cause contamination of the MAF sensor as well as improper fuel metering.

In summary, my recommendation to ensure you’re getting your best mileage possible is to get the car in as close to new condition as possible… with OEM replacement parts, not “upgrades”.

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A BIG +1 to mountainbike’s comment.