Removing Pre-cats

[jac114]

Will there be much improvement in performance if I can do away with the pre cats on my Gs and is there ant impications on doing so???

[DUNCAN]

Not sure of any implications on the GS model, but you will notice the difference after you remove em.

Did this mod on my IS a couple of months ago as a stand alone mod. Noticed the difference straight away.... No implications on the IS.

Do you know of anyone who's already done it to theirs ?

[Steve]

Does Decatting upset the Lamda Sensor?

Alot of soarers are decatted!

[DUNCAN]

Does Decatting upset the Lamda Sensor?

Alot of soarers are decatted!

Not on the IS models.

Not sure on GS !

[jac114]

Dont know of anybody that's done it. I was just wondering as my car is so old now that I doubt they actually do anything now apart from get in the way and restrict some of the air flow.. as for that sensor you talk of... what is it?

craig

[DUNCAN]

They're Lamda sensors, they send information to the ecu about the mixture of exhaust gasses.

[Keith Bowler]

What about MOT time.

Won't the car fail its emissions test without cats.

Just a thought.

[RX-Men-8]

Pre-cats heat up quicker as they are closer to the engine and smaller, so they work quickly after a cold start. When hot, a car can pass the emissions test without the pre-cats, as the main cat is then hot enough.

There is a sensor before and after the main cat, so that one will have to stay unless you want to fake one with a cat-simulator. The absence of pre-cats will not cause the engine management to complain about the sensor readings, so no extra measures are needed if you remove them.

Cheers,

RX-men-8

[jac114]

Pre-cats heat up quicker as they are closer to the engine and smaller, so they work quickly after a cold start. When hot, a car can pass the emissions test without the pre-cats, as the main cat is then hot enough.

There is a sensor before and after the main cat, so that one will have to stay unless you want to fake one with a cat-simulator. The absence of pre-cats will not cause the engine management to complain about the sensor readings, so no extra measures are needed if you remove them.

Cheers,

RX-men-8

thats the bit i needed to know... Its only a thought process at the moment just was not sure if it would bugger the ecu

[Keith Bowler]

Can you explain how you would simulate the presence of a CAT. I presume the EMU requires chipping of some description.

I have often wondered about replacing my exhaust without the CATs but have always been put off by possible failure on emissions test come MOT time.

[RX-Men-8]

Basically these are sensor simulators that give fake readings for use when a Catalyst converter is not present (usually race cars). The ECU would then be happy and not put the engine in its emergency program. This would be a quick and dirty option compared to a custom ECU mapping of the engine to run without a cat (and the other performance mods). Removal of the main cat is especially beneficial to performance if the engine is being turbocharged or supercharged.

For road cars I would recommend against it, because almost certainly removing the main cat will cause your car to fail the emissions test.

Cheers,

RX-Men-8