Modifying CAT convertors

[Zoro]

Hi all,
has anyone removed the original cat convertors and drilled out the "guts" to improve performance. Obviously its illegal (if you get caught) but is this an option rather than buying the high flow ones?

[sand_man]

yeah my boss did it on his 5L (he's an idiot).
It made no difference.

[VY CHRISSO]

Yeh I did it and I lasted a week before I went and had 2 new ones fitted along with a complete new system.
Removing the contents of the cat made no change to the performance, maybe worse, and gave it a tinny sound!! One of the few things I will that I wasted my time with!

Hope this helps.....

[V85000i]

depends though, if you don't have the cash just yet to get a new one, bashing the old one out will improve performance on a 100,000km+ car, because they get worn out and block up, it happend to me, on my old car, it couldn't rev over 3000rpm, discovered it was the CAT, bashed it out and went better than it ever did, but on your car being new, it might not do much.

[VY CHRISSO]

If your going to do it, don't just empty the cat and bolt it back on... doing this will create a lot of turbulence in the system and you will loose high rpm power!! At least fit a piece of pipe through the guts of the cat, to stop the air entering the cat and spiraling inside it before it exits to the rest of your system..

[Cobez]

Or just buy a high flow one.

They aren't expensive and it saves trouble from the law if you get busted.

[Not_An_Abba_Fan]

Not to mention all the crap you are spewing into the environment without a cat.

[sand_man]

dumb idea full stop

[vr_owner]

a highflow one fitted cost my brother $350. for a 3inch... not sure what brand.

[AttaBoy]

Don't do it. Do it the right way - buy a high flow unit.

If you can't afford it then save up.

[jules]

Originally Posted by Not_An_Abba_Fan

Not to mention all the crap you are spewing into the environment without a cat.

on anything more than 10 years old, i can't imagine the cat doing anything. the precious metals would be inert or worn away by then.

not that this would be any kind of defence from the EPA

[greenfoam]

I've gteched a 1/4 mile with my car (back when it was slower) with a blown out cat that came with it = 14.7 changed it to a good cat = 14.7. It makes no difference on a near stock car and that was a 5 litre

Edit, I will say though if anyone tells you a bashed out cat makes your car go faster, they are just imagining things because it will make your car quite alot louder and infact it's pretty easy to tell which cars have hollow cats just on the sound, I guess people think louder is faster

[greenfoam]

Originally Posted by jules

on anything more than 10 years old, i can't imagine the cat doing anything. the precious metals would be inert or worn away by then.

not that this would be any kind of defence from the EPA

The cats on VN's are solid not just coated like some newer ones, they will last forever or untill they hit something on the road and break into pieces. The metal in them alone is worth 50 bucks at a scrap yard. The reaction that cleans the exhaust doesn't take the metal away

[jules]

a catalytic converter works by means of a chemical reaction. the catalyst is the precious metals inside it, such as paladium and stuff i believe.

by definition the more exhaust flow through, the less catalyst there will be. however i have no idea how long it takes to wear out in practice..