Catalytic Converter Autopsy

[Weldangrind]

Spud's recent comments about catalytic converters prompted me to post these pics. This is a catalytic converter and air injection reactor (AIR) pump assembly from a 125cc Chinese dune buggy that belongs to member Sucksqueezebangblow. I had a spare exhaust pipe from a 50cc quad that I donated to get rid of the smog junk.

The first pic shows the whole assembly, and the arrow indicates the direction of exhaust flow. Bike and quad owners with catalytic converters will recognize this as the bulge in the exhaust header.



The idea behind the AIR pump is that it draws a bit of fresh air (usually from the air box) on the exhaust stroke, and sends it into the exhaust stream. You can see how the tube that connects to the exhaust pipe is on a slight angle, which helps to create the venturi effect. The inside of the valve is simply a reed valve (like on a two-stroke) that prevents exhaust from travelling backwards towards the air box.



Finally, this is a shot of the honeycomb catalyst within the bulge in the pipe. Yeah, that's not restrictive. :roll: The catalytic converter and the AIR pump aren't actually related, they just happen to be mounted near each other.

[sucksqueezebangblow]

that couldnt have been taken in your carport i can see the floor

[Weldangrind]

You suck. And it's not a carport, it's a shop. Learn some manners, or no more donuts.

[sucksqueezebangblow]

lol sensitive.......alright its a GARAGE but still way to clean....i dunno looks like a tim hortons table

[Weldangrind]

As part of your membership here, you're required to update us about the mods to your dune buggy WITH PHOTOS. Get on the stick man.

[lego1970]

Good post Weld.

From a guy with very limited knowledge on chemistry and or chemical engineering, ( I do know the melting point of chedder cheese and can cook a mean grilled cheese sandwich :P ) I have to say that I do find it very fascinating how the chemical engineers know how to coerce the atoms to bond in a way in which they desire based on a little metal and heat. Not to mention the abilty make a machine that can detect what the elements are in a certian gas. The gas spectrometer is an awesome machine. It baffles me that guys come up with stuff like that. Heck I get stumped on trying to balance my checkbook :?

[SpudRider]

Thank you for the tutorial, WaG. I've been told the exhaust pipe is double-walled around the catalytic converter. Is the entire exhaust pipe double-walled? How much heavier are exhaust systems which contain catalytic converters?

Spud

[Weldangrind]

On this specific cat, only the cat housing is double walled, and the cat / AIR pump assembly weighs about one pound. I doubt that the entire exhaust system on any China bike is double walled, aside from the cat.

[SpudRider]

No offense meant, but that catalytic converter and air pump are ugly! 8O The Chinese exhaust systems are notoriously heavy, and restrictive. :( I think the first task for any new Chinabike owner is to replace the stock exhaust system.

Spud

[Weldangrind]

My thoughts exactly. Member sucksqueezebangblow reports that his kid's dune buggy woke up after ditching the smog junk.

[SpudRider]

Originally Posted by Weldangrind

My thoughts exactly. Member sucksqueezebangblow reports that his kid's dune buggy woke up after ditching the smog junk.

I believe! I'm amazed the engine can exhale at all through that nasty catalytic honeycomb. 8O

Honda is notorious for adding SMOG pumps to their engines; however, I don't think Honda ever resorts to catalytic converters. :roll: I was a happy man when I removed the SMOG tumors from my XR650L.

The exhaust system on my Zong was very heavy, and highly restrictive. I can't believe I waited so long to remove it, and install an FMF Universal Spark Arrestor! :roll:

Spud

[Weldangrind]

I agree that the catalyst is terribly restrictive, but I don't think that the AIR pump (in this application) hurts peformance. In fact, the idea is that a burst of air will enter the hot exhaust stream to provide fuel to further burn any unburned hydrocarbons. That might make the folks at the EPA happier, but on a child's machine it's just another device to get in the way and break on a tree or a rock.

I had a similar device on an old four cylinder Chev when I was a kid, and the internal valve failed, which provided a steady stream of oxygen all the time. Every time I lifted the throttle to shift gears, BANG! Shortly thereafter was the first time I ever performed a smog-ectomy.

[SpudRider]

Originally Posted by Weldangrind

I agree that the catalyst is terribly restrictive, but I don't think that the AIR pump (in this application) hurts peformance. In fact, the idea is that a burst of air will enter the hot exhaust stream to provide fuel to further burn any unburned hydrocarbons...

Thank you for elaborating, Wag. Indeed, all reports I have read indicate the "air pumps" don't hurt performance. However, they certainly are ugly! :P

Spud

[FastDoc]

Originally Posted by lego1970

Good post Weld.

From a guy with very limited knowledge on chemistry and or chemical engineering, ( I do know the melting point of chedder cheese and can cook a mean grilled cheese sandwich :P ) I have to say that I do find it very fascinating how the chemical engineers know how to coerce the atoms to bond in a way in which they desire based on a little metal and heat. Not to mention the abilty make a machine that can detect what the elements are in a certian gas. The gas spectrometer is an awesome machine. It baffles me that guys come up with stuff like that. Heck I get stumped on trying to balance my checkbook :?

Creation is amazing.

The more I learn, the more degrees I accumilate, and the older (wiser?) I get the more I am amazed with Creation and the more certain I am of the Creator.

It's good that different people are blessed with different abilities. Some guy is a scientist and understands catalysts but can't fix his sink. The plumber makes quick work of the sink but can't fly a plane. The pilot flys fine but can't play golf. The pro golfer can't fix his Harley and so on...

[FastDoc]

Originally Posted by SpudRider

No offense meant, but that catalytic converter and air pump are ugly! 8O The Chinese exhaust systems are notoriously heavy, and restrictive. :( I think the first task for any new Chinabike owner is to replace the stock exhaust system.

Spud

Ugly indeed. We de-smogged the KLX's while we were at it, even though none of the plumbing could be seen behind the shrouds. Just knowing it was there.... :wink: