Cat removal on Chimaera 4.3

[gavster]

Hi PPL,

I have recently purchased a 4.3 Chimaera and am wholly enjoying the experience.

Can anyone help with the following...

My Chim has had the cats removed, does anyone know the procedure for this, the benefits(apart from the noise!)and how this may be reversed?.

I guess the ECU will have been re-programmed and maybe some other sensor modified / changed. The lambda sensor connections have been disconnected and are ty-wrapped in the engine bay, the sensors are still in the headers, just disconnected, anyone know the reason for this?

Any info is greatly appreciated.

Bring on the summer.

Gavster

[GreenV8S]

quote:does anyone know the procedure for this, the benefits(apart from the noise!)and how this may be reversed?.

The obvious benefit is the thrill of knowing that your car is technically illegal and is likely to fail it's next MOT, and it is a modification which will invalidate your insurance if you haven't notified your insurers.

The benefits are more noise (no track days for you then!) and potentially about another 10 BHP if it is mapped correctly afterwards. Since you still have the lambda sensors you must presumably still have the original cat manifolds, which have a little pre-cat in each bank as standard. I wonder if they were taken out too? Silly not to but you never know.

The basic procedure for doing the mod is take out the pre-cats from the manifolds and replace the main downpipe with a pre-cat version, or remove the cat from inside it. A common way to do this is replace the manifolds and downpipe as a set, which leaves you with nowhere for the lambda sensors to go. Since the main purpose of the lambda sensors (apart from getting you through the MOT) is to protect the cat, you can run without them but in order to do this you need to get the ECU remapped to run open loop. But if you have kept the original manifolds (as you seem to have done) then disconnecting/removing the lambda sensors and remapping the ECU isn't fundamentally necessary and you *can* stay in closed loop mode.

Re-catting is basically the reverse, bearing in mind the pre-cats are entirely optional and probably best left out, the main cat which does all the work costs quite a few hundred quid, and to go back to closed loop mode you will have to get the ECU remapped again. Depending how the previous mapping was done, I think it *may* be possible to restore the original map with the tune resistor, as I understand the alternate map on non-cat cars is often a cat map. But you would need to get an expert such as Mark Adams to find out whether this was the case with your car.

Hope this helps,
Peter Humphries (and a green V8S with cat)