Standard cats?

[Peppe]

What cpi is a standard cat on a SP6? 200, 300 or 400

[NTEL]

400

[Peppe]

Thanks !

What would be the benefits of using 200 cpi (sports cats) instead of standard?

My thoughts are that less restriction gives a couple or so more bhp, but what happens with the temperature around the cats, are the sports cats cooler since the exhausts pass through easier?

[dvs_dave]

My understanding is that cats get to the temperature they do because of the catalytic reaction taking place in them, and it's this reaction that generates the excess heat rather than the exhaust gas.

So in short, sports cats will get just as hot as normal ones.

[Basil Brush]

I always thought it was the other way round Dave, hence the reason they are mounted close to the engine so the gasses are hottest when they enter to aid efficiency? I am wrong a lot though.

[dvs_dave]

They put them close to the engine as the "light off" temperature for the catalytic reaction is pretty close to normal exhaust gas temps. Once they're "lit" the chemical reaction taking place in them generates additional heat above that of the exhaust gasses.

This is the reason why on a speed 6 car, de-catting it results in less heat soak as less heat is being generated in the engine bay. The actual temperature of the exhaust gases exiting the engine doesn't change.