Are these things any good on an FD... compared to the stock cat, for example? They seem to run a bit over $400 online.

 

What are your objectives for it?

They're good for cleaning up the smell, but not so good at passing strict emissions tests.
Also, some users report melting/clogging due to extreme rotary heat. So, application is an important factor, too.

 

Any reason not to go the tried and true route of the Bonez cat? It's about the same price and everyone has had good results with it.

 

I have an emissions test coming up and I am reading horror stories about Ontario's new Drive Clean testing regime. Random seems to advertise more – I'll look into the Bonez cat as well.

You would think Random would stop selling the product if it couldn't endure a turbo rotary's exhaust heat...

My FD has a street port and a sequential turbo with A'PEXi Power FC, Greddy PRofec-B Boost Controller, and some bolt ons.

 

I made 454 rwhp with a random cat. Only a couple hundred miles on it so far. Its cleans up the smell fairly well once warmed up, but I'm not sure it would pass emissions on a heavily modified/ported car.

 

If the cat is relatively low mileage and warmed up, it will get the job done. You still need a stable idle without misfire and a functioning airpump.

Every cat experiences thermal aging from heavy loads. The more heat you throw at it, the more it will degrade. If there's more precious metal it will last longer, but that means more money.

 

I see you're in Canada. I just bought a new Bonez and it ended up costing $501 USD shipped which converts to $568 CAD, plus $93 in UPS brokerage fees, for a total of $661. Keep that in mind if you're considering that route...

 

Thanks! I looked through some paperwork from when I bought my FD (over a year ago) and it says "new Mazda catalytic converters" on the mod list, so I hope I'm covered for the time being.

 

If you weld two cats together and have a single pipe with two cats on it, is that going to cut out the bad emissions twice as well? And is that safe for the motor? Because that seems completely reasonable but I have never seen anyone do it.

 

It sounds silly at first, but lots of cars come with 2 cats in-line to each other. The USDM FD does.

The root cause of failing an emissions tailpipe inspection is usually a failed airpump/port air system, a failed cat, bad plugs, or unstable idle. It's not necessary to add another car because all you need is 1 main cat that's working right. The stock front cat isn't even needed to pass an emissions tailpipe inspection. Cats are also ineffective if the airpump isn't working.