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

[Chris914n6]

First a disclaimer... I put it on my Nissan swap. Being from a fwd I copied the under engine Y tube into a single that goes thru the cat and into an SC 1 in 1 out banana muffler.

For the T4s, apples would be a triad or similar single exit header.

Science stuff.
Heat is fine plenty of air flow under the trunk. Back pressure is practically none.
You don't need an o2 sensor but you do need a well tuned engine as too much gas or oil will burn out the cat.
Cats were first installed with TBI injection, which is really just a carb with an injector or two in it and is super rudimentary.
That being said, you really should install a wbo2 sensor & gauge to tune the engine first, specially carbs. 12point7 is likely the cheapest good setup.

We still have the sniffer test. Back when I had carbs and later the 2.0fi, it would barely pass under 250 ppm HC. The 97 Nissan setup was less than 1, which was actually a problem because the sniffer detected fresh air and wouldn't accept it. That's a big reason OBD2 cars are computer tested because the sniffer can't read that low.

That is a rear o2 in the pic. It's sole purpose is to check the function of the cat and for me keeps the CEL off until there is a real problem.