apparently there is a noise difference with lower cell count cats, which makes sense i suppose, as there is less impedance in flow and a bigger body would resonate the note a little?

Hey mate,

From a legal and roadworthy standpoint all you need is a functioning catalytic converter, the main issue that people see with cats is whether or not they are emissions compliant. The cats are Euro 2 Emissions complaint which means they are compliant on most cars made up until 2003. However, even though the cats may be compliant, the car may not be as it depends on any other mods done. For example, an early LS1 with a cat-back exhaust and a basic Intake will comply with emissions, however, an LS1 that has cams, heads, extractors and a mafless tune will most certainly not. It does depend on each application and the laws vary from state to state. Because of all these variables and differing laws it is hard to make a clear cut statement. In saying that though, no High Flow Metal Core 100CPSI Cats are Euro 3 emissions compliant, despite what some may claim, otherwise it just wouldn’t be a high flow cat.

I know alot of people are worried about emissions which is why i have also have the range of 200 and soon to be released 400 Cell Metal Cats which still offer great gains over stock units and are much more friendly for the environment. The 200 Cell cats are available in 2.25”, 2.5” and 3” and still utilise the same 4” body as the 100 Cell cats. When run in a twin cat configuration on a V8 the performance difference to the 100 cell versions is minimal.

George

Most are 400 cpsi ceramic infill cats. I have heard the difference in power between the 100\200 cpsi is within a kw or so. Better stay with the 200 because the fines will not be worth it if it doesnt pass.