Gutting catalytic converter

Is the gas flow through a factory converter better with, or without, the
honeycomb filling?

Some people say it's good to remove all or part of the insides, others say
that will make the gases stall in the chamber. But some cars have an
expansion chamber as a silencer anyway, don't they?

On Thu, 27 Jan 2005, Mark W wrote:

> Is the gas flow through a factory converter better with, or without, the
> honeycomb filling?

Depends. Is the core melted or is it OK?

> Some people say it's good to remove all or part of the insides

Some people are idiots.

> others say that will make the gases stall in the chamber.

Others are idiots, too.

What is it that you're trying to achieve?

Low restriction exhaust systems are usually positive for economy and power.

If I am correct, however, gutting the catalytic convertor can cause you
issues of a legal nature. I'm not saying you will end up in prison,
but it isn't the path to take.

Depends, can you afford the $50,000 fine?

Mark W wrote:
> Is the gas flow through a factory converter better with, or without, the
> honeycomb filling?
>
> Some people say it's good to remove all or part of the insides, others say
> that will make the gases stall in the chamber. But some cars have an
> expansion chamber as a silencer anyway, don't they?
>
>

On Thu, 27 Jan 2005, HLS wrote:

> Low restriction exhaust systems are usually positive for economy and power.

Well...no. This generalized statement is flatly not accurate, because it's
not nearly specific enough. This is not 1977 or 1987 we're living in, when
most vehicles' factory exhaust systems were highly restrictive.
Significantly changing the backpressure characteristics of the exhaust
system can have significant *DOWNWARD* effects on fuel economy and
driveability.

> If I am correct, however, gutting the catalytic convertor can cause you
> issues of a legal nature.

It is a Federal crime, yes.

> I'm not saying you will end up in prison, but it isn't the path to take.

Right on both counts here. The correct fix for a clogged catalyst is a
replacement catalyst. The correct fix for an unclogged catalyst is to
leave it alone.

DS

"KENG" > wrote in message
. com...
> Depends, can you afford the $50,000 fine?
>
>

I live in the UK where my vehicle doesn't legally need a converter.

So, I was wondering how the gas flow through an open chamber compares with
the gas flow through a chamber filled with converter filling?
I know the open chamber will not be as good for gas flow as a straight pipe.
Nor is a space filled with a honeycomb type filling.

On Fri, 28 Jan 2005, Mark W wrote:

> I live in the UK where my vehicle doesn't legally need a converter.

Wrongo, check your laws again. It's just as illegal to remove a converter
on a car originally so equipped in the UK as it is in the US...and
Canada...and the European Union...and Australia...and Japan.

But, to answer your question: You will not gain anything by gutting the
converter.

"Daniel J. Stern" > wrote in message
n.umich.edu...
> On Fri, 28 Jan 2005, Mark W wrote:
>
> > I live in the UK where my vehicle doesn't legally need a converter.
>
> Wrongo, check your laws again. It's just as illegal to remove a converter
> on a car originally so equipped in the UK as it is in the US...and
> Canada...and the European Union...and Australia...and Japan.
>
> But, to answer your question: You will not gain anything by gutting the
> converter.

A convertor will add some backpressure. In theory, the more back pressure
you remove, the better it might be able to perform. In practise, however,
the gains for this type of 'modification' are next to nothing for the
ordinary driver and ordinary engine.

Clearly, F1 cars do not run catalytic convertors. There is a weight penalty
as well as a performance penalty. But not for us who drive the typical
street 'turds'.

"Daniel J. Stern" > wrote in message
n.umich.edu...
> On Fri, 28 Jan 2005, Mark W wrote:
>
> > I live in the UK where my vehicle doesn't legally need a converter.
>
> Wrongo, check your laws again. It's just as illegal to remove a converter
> on a car originally so equipped in the UK as it is in the US...and
> Canada...and the European Union...and Australia...and Japan.
>
> But, to answer your question: You will not gain anything by gutting the
> converter.

A convertor will add some backpressure. In theory, the more back pressure
you remove, the better it might be able to perform. In practise, however,
the gains for this type of 'modification' are next to nothing for the
ordinary driver and ordinary engine.

Clearly, F1 cars do not run catalytic convertors. There is a weight penalty
as well as a performance penalty. But not much for us who drive the typical
street 'turds'.

Daniel J. Stern wrote:

>It's just as illegal to remove a converter on a car
>originally so equipped in the UK as it is in the US...and
>Canada...and the European Union...and Australia...and Japan.

One exception I know of is for 1975 and 1976 VW Golfs made for the US
market. The rate of converter failures was so high that VW issued a
TSB instructing mechanics to gut it and make some changes to the
carburetor and EGR system.