View Single Post
Dansvan Dansvan is offline
Join Date: Oct 2011
Posts: 286
Originally Posted by javadog View Post
I’d like you guys to explain to me how the material from a damaged cat can get inside the crank case of an engine.
The cat is built into the exhaust manifold. Very close to the exhaust valve. The variable valve timing strategy holds the exhaust valve open under certain conditions to allow exhaust back into the cylinder on the intake stroke to dilute the mixture thus reducing NoX. EGR without an EGR valve. The top of the cat substrate takes the most abuse and deteriorates. It is sucked back into the cylinder accelerating wear. The more wear, the more oil blows by and hits the cat substrate over heating it causing more damage and more material breaks off and ends up in the cylinder. Vicious cycle until it wears out. The cat substrate goes by the worn rings and cylinder bore as combustion blow by. This is real, it has happened to several manufacturers. Ever increasing emission demands require closer cats for faster light off. In order to
Keep costs down material corners get cut. Some aftermarket tuners (on Nissan I believe) have gained 50-70 hp just by changing the VVT strategies.

That’s the simple version. There’s obviously more to it. Exhaust reversion, sound (Pressure)waves, etc.

Last edited by Dansvan; 09-10-2020 at 12:14 AM..
Old 09-10-2020, 12:06 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #50 (permalink)