Interesting:

So on a production car they put the cat as far forward as possible (in the down pipe on some cars?) and I believe this is to get the heat to the cat as soon as possible (as a cat needs to warm up to work) whereas on a Rally car they put it as far back as possible to stop it from melting due to their extremely high exhaust temps? Does an anti lag car really have that much higher temps in the exhaust? Would be interested to know how many extra degrees we are talking.

One last thought, I recall being told that an exhaust pipe needs to be larger, closer to the engine as the volume of the gas (due to it being at its hottest) closer to the engine is higher, and as it travels up the exhaust it cools and thus the volume of gas reduces so the bore of the exhaust doesn't necessarily need to be as big. So this would would hint towards a cat (being a restriction) being better placed towards the back of the exhaust as it will create less of a restriction at that stage?

On that note, I was never happy when I was told I had to keep cats on my M3. It reads the gas before and after the cat and goes into a limp home style mode if there is not any difference. So it is either expensive "race" cats or a new style ECU that doesn't read before and after, or some adaption to my current ECU that means it no longer cares (no one seems to be able to do that yet).

Cheers
RW

Cheers

RW