High Flow Cat?

[jbandalan]

Can anyone tell me what what kind of cat converter this is?

Found out this on my car and wondering if it's high flow etc.

[hypergear]

Its a compliance cat, it works extremely well once punched through.

[jbandalan]

Thanks!

[XKLABA]

Works better once replaced with a better cat, I like having a working cat as once they "light up" they create heat and hot gases move faster then cold gases

[Ben C34]

Works better once replaced with a better cat, I like having a working cat as once they "light up" they create heat and hot gases move faster then cold gases

Are you saying having a cat is better than not having one for performance?

[XKLABA]

IMO and not based on any real facts, on a full exhaust yes!!, providing it/they can flow what you need to and don't have any sharp lips/edges to cause turbulence, I run 2 x 5" bodied 3" cats in my 34

Short exhausts, ie side pipes etc, different story

[Dose Pipe Sutututu]

I don't understand.. how can adding a restriction increase gas velocity & movement of more volume?

I understand once air cools, it's more dense thus creating a pressure difference pre/post cat.. however it's not enough to warrant any kind of vacuum effect to accelerate exhaust flow.

[GTSBoy]

I'd just like to point out that hot gas = faster gas = better extraction/power/response/whatever is a myth that is unsupportable by both theory and practice.

The faster a gas is moving in any conduit the higher the frictional losses and therefore the higher the pressure drop. Given that the outlet end of the exhaust pipe is always at atmospheric pressure, that means that the pressure at the other end of the pipe has to be higher. And that is not good.

There are a couple of complicating factors. The density varies inversely with temperature - which is why the gas speeds up as it gets hotter (for the same mass flow). The pressure drop varies linearly with density. So a decrease in density looks like it will reduce pressure drop. But sadly, the pressure drop increases with the square of velocity. So if you multiply all those factors out, the pressure drop effectively varies linearly with temperature.H

Hotter gas = more pressure drop = bad.

The only time when hot gas is a good thing is when the energy in it is driving something desirable. Scavenging pulses in an extractor manifold, or a turbo's turbine are about the only relevant ones I can think of wrt cars.