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I don't know why people are traditionally so reluctant to just put a bigger cat on the car. It works fine, passes sniffer tests (and visual tests if well done) and hurts performance less than most mufflers do.
It's illegal to modify OEM emissions equipment, which includes making it better. Whether or not you would get caught or an inspector would care is a different story.
 

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Discussion Starter · #22 ·
Steely,

Good job. Thanks.

Yrs ago, I thought we were moving towards roadside sampling all over the damn place. Too costly or time consuming? I figured on cameras catching the grossest.

By "bigger cat" do you mean wider diameter??

From my perspective, given like I want everyone's grandchildren to breath clean air, cats are not a big deal street cars. Some ppl remove them for better sound; an even lamer excuse. Get a better exhaust system.
 

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2005 Elise LSS Saffron Yellow
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It's illegal to modify OEM emissions equipment, which includes making it better. Whether or not you would get caught or an inspector would care is a different story.
True as far as it goes. I haven't bothered to look into federal and CARB requirements for converters, but universal cats are sold to somebody, which means they meet requirements somewhere. Further, at a certain point, the OE replacement cat is no longer available. A universal would be the only logical solution in that case. I suspect the law allows for this, and further suspect that it doesn't pay attention to the flow capacity of the replacement.

Yrs ago, I thought we were moving towards roadside sampling all over the damn place. Too costly or time consuming? I figured on cameras catching the grossest.
Mostly obsoleted by events - current versions of OBDII include a post catalyst O2 sensor, which means you can measure the effectiveness of the cat with the ECU/PCM. As long as you have reasonable surety that the software in the ECU/PCM is honest and as certified, then you (pretty much) know if the car is meeting emissions standards just by pulling the OBDII logs or, at most, hooking up to the OBD port and monitoring upstream and downstream 02 sensors while driving the car on an IM240 cycle.

That's why they're going after software vendors so hard - if they can't trust the code, they have to go back to tailpipe testing in some form.

Roadside testing is a pretty finicky system. I suspect production-izing it would help a lot (ours was one step away from being breadboard and used a gas dryer igniter coil and mirror as a broadband IR source). You also have to locate and set up the system in an unobtrusive way on a single-lane road or at a low traffic time on a multi-lane road. We preferred on ramps because people hit the accelerator to get up to speed, giving you a good picture of the engine working hard.

To work as an enforcement tool you need something unobtrusive that has an IR emitter on one side of the road, the IR spectrometer on the other side of the road, and a camera hooked to a license plate reader in the right spot to get a capture of the plate right after the car crosses the beam. The broadband IR source takes a fair amount of power, so there's a little generator chuffing along over there, or it's wired in somewhere. It can't be permanently mounted because people get wise to it when the tickets arrive.

All you have to do to avoid getting a ticket is coast through the beam...

A complicated and not-cheap problem. Further, if it's manned, that's both expensive and obvious, and if it's unmanned it's very likely to be vandalized by somebody who got a fix-it ticket(see GATSO destruction pictures from the UK).

By "bigger cat" do you mean wider diameter??
I mean higher flow capacity. Some cat constructions (metal coil) have lower resistance per unit catalyst area than the ceramic matrix commonly used. Most vehicles can put a bigger cat in the stock location pretty easily. Manufacturers tend to make them small both because smaller is cheaper and because they light off faster, which helps with the 124 second emission numbers.

From my perspective, given like I want everyone's grandchildren to breath clean air, cats are not a big deal street cars. Some ppl remove them for better sound; an even lamer excuse. Get a better exhaust system.
I'm planning on replacing the restrictive #1 muffler (it has two) on the Celica with a cat sized for a ~4L v6 when I put a header on the car which will remove the header-mount cat. Get my cake and eat it too, and keep the car from getting too much attention because of an obviously not-stock exhaust. Legal in this jurisdiction, especially as the car is over 25 years old. It'll probably work better than the worn-out stock cat, too.
 

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Discussion Starter · #24 ·
Thx again.
 
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