Catalytic Converter Question

[Cristobal]

I know in the past there were cars that would re-circulate exhaust gas through a ceramic element catalytic converter, and vent some back to the cylinders. But if fragments of the ceramic element broke off, this could ruin the engine.

Are there any new cars these days with this same issue?

 

[Cujet]

I'm not aware of any current cars that use post catalyst EGR.

However, on heavy duty diesel engines, a catalyst is sometimes used in the EGR system itself to help keep in clean. I'm fairly sure (but not 100% certain) these are metal matrix catalysts, not ceramic.

 

[splinter]

Originally Posted By: Cristobal
I know in the past there were cars that would re-circulate exhaust gas through a ceramic element catalytic converter...

Which cars were those if you don't mind me asking?

I'm familiar with AIR systems pumping into catalytic converters to help them 'light off' but EGR
is invariably sourced upstream of the cat in gasoline-fueled applications afaik.

 

[eljefino]

I think you're thinking of nissans that had pre-cats in the manifold, and valve overlap led them to occasionally suck exhaust backwards.

 

[CBR.worm]

Yes, I believe eljefino is correct. Some Nissans would suck cat bits back in through the exhaust valves.

I think there were some non-nissans that did this as well.

Nissan also had butterfly screws that could come loose and end up in the engine around that same period.

 

[JTK]

Yep, the only thing tubed into the cat would be for air injection.

 

[Cristobal]

So such systems are all discontinued?

 

[Cujet]

Originally Posted By: Cristobal
So such systems are all discontinued?


I guess that's one way to say it.

I don't believe there are any cars with post cat EGR systems.

But, as I mentioned, there are large diesel engines with cats built in to the EGR system.

 

[artificialist]

The Honda R18 has an EGR valve mounted post-cat. I'm not sure if that was a problem.