Pre-cat removal - gut or aftermarket manifold?

[J4ck100]

Hi All

I'm getting paranoid about my Pre-cats as hearing a slight fizzle from the exhaust on the over-run which i didn't notice before.

Would you replace with a Toyosport manifold or would you just gut the existing one?

Thanks

[Joesson]

@J4ck100
Typically the pre cursor to pre cat failure is high oil consumption, the reason for that is considered to be gummed piston oil control rings caused by bad design of OE pistons exacerbated by extended oil change intervals.

This subject has been discussed on here and elsewhere for almost as long as our cars have been around.

When I got my 2 in 2011 it was not unpopular to de cat the original manifold as the OE manifold is basically of better quality than many after market manifolds.
When I did that to mine I also fixed the rattling in line Main cat and generally got to know the underside of the car.
De cat or replacement will require new gaskets, manifold to head nuts, and likely some studs. So the price difference between the two methods will be at first thought the manifold cost. But then there is the question of wrapping, with heat resistant tape, or not. Again a subject of some debate.
I have had no problem with emission levels at MOT time, and I understand the same applies to a new manifold so you pay more or less and take your choice.

[thetyrant]

Gutting the pre-cats is better than not in terms of engine health,  but its also not ideal due the poor gasflow from having 2 big empty chambers in the exhaust system so close to the head, for sake of £100 for aftermarket manifold i would just do it right with one of those

[Ardent]

Hi All

I'm getting paranoid about my Pre-cats as hearing a slight fizzle from the exhaust on the over-run which i didn't notice before.

Would you replace with a Toyosport manifold or would you just gut the existing one?

Thanks

I would identify and confirm the source of the fizzle 1st.
As per @Joesson are you using any oil?
The spacers hidden by the cat heat shield often produce a rattle if that's equivalent to a fizzle.
If you go the aftermarket route. Don't forget to inform your insurance of the perceived performance upgrade.

[J4ck100]

Hi All

I'm getting paranoid about my Pre-cats as hearing a slight fizzle from the exhaust on the over-run which i didn't notice before.

Would you replace with a Toyosport manifold or would you just gut the existing one?

Thanks

I would identify and confirm the source of the fizzle 1st.
As per @Joesson are you using any oil?
The spacers hidden by the cat heat shield often produce a rattle if that's equivalent to a fizzle.
If you go the aftermarket route. Don't forget to inform your insurance of the perceived performance upgrade.

Are your pre-cats still present?

[Ardent]

Yes.
But mine is different to yours.

[Joesson]

Hi All

I'm getting paranoid about my Pre-cats as hearing a slight fizzle from the exhaust on the over-run which i didn't notice before.

Would you replace with a Toyosport manifold or would you just gut the existing one?

Thanks

I would identify and confirm the source of the fizzle 1st.
As per @Joesson are you using any oil?
The spacers hidden by the cat heat shield often produce a rattle if that's equivalent to a fizzle.
If you go the aftermarket route. Don't forget to inform your insurance of the perceived performance upgrade.

Indeed, one persons rattle could be another's fizzle!
To check the precats you need to remove the  two top O2 sensors and shine a light into the chambers hoping to see intact matrices.
To remove the sensors you will need an O2 socket spanner, you will need this for any manifold work anyway.

[Elektronic]

@J4ck100
I too became paranoid about the potential of the precats breaking up. A visual inspection proved inconclusive.  I eventually removed them only to find a perceived drop off in performance , the exhaust gas expanding into the large empty chambers and ensuing chugging noise at tick over. Ive since fitted Toyo aftermarket manifold. Engine note is crisper and no worries about the precats. My personal advise , if your concerned fit a Toyo.

[Ardent]

Or a Zero.
See mikeymeads recent post.
Very nice.

[Gregmorse]

There's no reason to NOT gut your pre-cats, if you live in the UK, it'll still pass the MOT, is relatively easy to do. Just ensure to get rid of ALL debris. ALso, you can check the condition of pre cats by removign the 2 oxygen sensors, the surface you can see down the hole should be totally intact with no dents/damage.

[thetyrant]

There's no reason to NOT gut your pre-cats, if you live in the UK.

There is!  a reduction in performance due to poor gas speed in the exhaust with the empty chambers, that said most wont notice a huge difference.

[Gregmorse]

Fair enough! I gutted my pre cat and upgraded to an aftermarket pre cat section, hardly noticed a difference