Adding a catalyst, or two, to a 914?!, It has already been done, I'd like to learn more… Options

[horizontally-opposed]

This thread prompted by an idea discarded long ago and revived by a recent post from @Chris914n6 elsewhere noting his decision to add a cat to his 914. Curious to hear thoughts on upsides and downsides with this idea. Feasible? Effective? Ineffective? Stupid? Sure to cook the engine's—or the 901's—oil? Or?

Talk about threads I thought I'd never start, but my 914 is pretty smelly in 2020 in a way it wasn't when I started driving it in the 1990s…because all cars have become so much cleaner and the older cars on the road back then are long gone now. Turns out, there are such products out there—and I am surprised by the price disparity.

https://www.holley.com/products/exhaust/cat...l/parts/2000124

https://shop.redline360.com/products/g-spor...gh-output-85030

[Mark Henry]

The cat won't last long with an aircooled, you would also need to run an emissions factory air pump system, you know that thing owners ripped off and tossed in the trash in the 70's-80's.

Cats like to run 14.7-14.8:1 so stoch or a bit lean, the reason most early FI ran on a narrow band O2 sensor. Running a aircooled at stoch would kill the aircooled engine, even with modern FI and anti knock sensors. With my'67 bug EFI and wide band, using nickies I've leaned out my 2.6 type 4, at just under 14:1 my head temp skyrocketed, at say 13.75:1 I have to be very careful of pulling hills, the best I can do with a comfortable margin is 13.5:1. Many cars would still be running carbs (at least into the 2000's) if cats played well with them.
Running rich, as our cars do, using a cat would help the reduction of CO and hydrocarbons but at the expense of NOx. Then add the fact they won't last long and it's hard to get enough heat into them to make the cat work, etc....

I looked into this as well (IMG:style_emoticons/default/wink.gif)

Now if running a FI watercooled conversion installing a cat makes perfect sense.

[horizontally-opposed]

The cat won't last long with an aircooled, you would also need to run an emissions factory air pump system, you know that thing owners ripped off and tossed in the trash in the 70's-80's.

Cats like to run 14.7-14.8:1 so stoch or a bit lean, the reason most early FI ran on a narrow band O2 sensor. Running a aircooled at stoch would kill the aircooled engine, even with modern FI and anti knock sensors. With my'67 bug EFI and wide band, using nickies I've leaned out my 2.6 type 4, at just under 14:1 my head temp skyrocketed, at say 13.75:1 I have to be very careful of pulling hills, the best I can do with a comfortable margin is 13.5:1. Many cars would still be running carbs (at least into the 2000's) if cats played well with them.
Running rich, as our cars do, using a cat would help the reduction of CO and hydrocarbons but at the expense of NOx. Then add the fact they won't last long and it's hard to get enough heat into them to make the cat work, etc....

I looked into this as well (IMG:style_emoticons/default/wink.gif)

Now if running a FI watercooled conversion installing a cat makes perfect sense.

^ Great input. Thanks Mark!

Suspect the much more sensible move for a carbureted air-cooled engine is EFI.