OBD1 vs OBD2 cats?

[SBC_cheyenne]

Hello, I'm thinking of buying a new high flow cat and I have a 95 c1500 with the 3" single pipe. I am curious the difference between an OBD1 cat and a OBD2 cat. Besides the o2 bung after the cat, what difference is there?

 

[GMRedline]

I am pretty sure the mechanical designs of the OBD1 and ODB2 cats are the same. Newer high flow cats are different then what came from the factory.

Here is the best post I have read about the difference between the two.

http://www.gmt400.com/forum/showthread.php?22752-Catalytic-converters&p=663417&viewfull=1#post663417

Here's my 89 K1500, 350 TBI. 3" system fr0m the Y pipe back. Mandrel bends, so it really is 3" from the y pipe right back to the tailpipe.

It has a "high flow "performance" converter, a 3" Cherry bomb elite muffler and aftermarket Ypipe:

http://www.youtube.com/watch?v=C2hz-msHMGo

Nice pleasing sound, not too loud (even with the slider window open), audible when you stomp it, makes people look twice when it rumbles, no stupid rattling, rasping crackling or popping, always nice mellow rumble even under heavy load. (I no longer own the truck BTW).

Loud exhausts are just.....well, loud. Loud is pointless. And irresponsible. And annoying. Loud very often mean less power, no matter what your impressions are. Not many know that. It sounds faster, it must be faster, right? Not necessarily....not necessarily.....

Rumble says "I mean business" and "I'm built right". Yes, that truck meant business: that was my built TPI/411 PCM engine....junked it because of frame and body rot or I'd still have it today. Was just too far gone. Sold the drivetrain to a guy who couldn't shove the money into my hands fast enough.

Here's a "simple simon" video on how it all works together:

http://www.youtube.com/watch?v=W6dIsC_eGBI

Basically, a "high flow cat" simply is made using modern methods. Most modern converters present very little restriction. "High flow" is sort of marketing hype for replacement convertors. The do flow more than the original style converters, but they are usually simply new convertors made the modern way.

Old way:

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Modern way:

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Further flow restriction reduction can be had by an aftermarket manufacturer "messing" with the "honeycomb" sizing and that's what they will list as "high flow". Regardless, they all pretty much meet OE spec, regardless of what they call it.

Keeping a cat costs you nothing more than a couple bucks up front. It keeps you legal and more importantly: it reduces the nasty stuff coming out the tailpipe. Contrary to popular myth, convertors are not a bad thing nor are they performance killers. "gutting cats" is an old mindset from about 1970-1980 or so when they were the older pellets style catalyst and were prone to failure from carburetors imprecise fuel metering gagging them solid (well, also the leaded fuel that was being phased out). They are a passive device and quietly go about their business until something ruins them. Up to that point, they are essentially no cost on the engine and an asset to everyone by reducing emissions.

You know, the stuff that causes more/stronger hurricanes, bigger/more thunderstorms and hail, more/stronger Tornadoes, and so on. If you think that doesn't cost you anything, think back to what happened to fuel prices after AKtrina and how long it took for them to level out again. It also is the stuff that makes it harder for you and others to breath in cities or if you are in a "tailpipe" region (ask anyone in the North East US or Atlantic Canada about that one) and if you have kids, well.....you're not selling their future environment for vanity's sake or that 5 hp (or less) that won't make a snot bit of difference to you on your usual way to work drive anyways.

I'm not an "environmental freak", a "tree hugger" nor the "enviro police" but I do know the changes I've seen in just my short 50 years on this earth and I also know far to much about what is coming out of my cars to ignore it. I replace my convertors when/if they die and I keep my vehicles in top running condition. It saves me money in the long run (ie: fuel, running costs and maint), gives me a stone axe reliable vehicle and it makes me feel good to know I'm doing something to make a difference (however small) in the world that I am going to hand over to my daughter once I'm gone. I see the OP has a picture of a young spud in his avatar pic, think about him/her when you chuck that piece of straight pipe in your exhaust...just pause and think....

If the cat gets fragged from running in short order, it's not the cat that's the problem. Your engine is not running right, usually rich. That costs you money in ruined parts and fuel mileage. Cats don't fail unless something causes them to fail...or they're 20 or so years old.

Nothing lasts forever....

 

[SBC_cheyenne]

Very helpful, thanks.

 

[Hoplite]

Sticky?

 

[Supercharged111]

That quote really downplays the impact of honeycomb sizing vs flow and its ability to clean and how long it will last. OE converters are more heavily laden with precious metals and the like which makes them more effective and makes them last longer. I believe OE cats are required to last 8 or 10 years. Aftermarket cats with less precious metals and fewer cells won't filter as good for as long, but they will flow more and whether or not that flow gives you more power is something you'll have to try yourself. As was mentioned, modern OE cats really are not all that restrictive. The problem on the GMT400 is that the half ton head pipes are only 1 7/8" and the cats are installed on this piping, so yes they are restrictive on a GMT400. 3/4 ton head pipes are 2 3/4" and won't hold you back at all.