help exhaust glowing

wrote in news:1157715455.446907.8530
@d34g2000cwd.googlegroups.com:

> TeGGeR® wrote:
>
>> I once saw this exact thing on an '80s Lada Riva (Russian 4WD).
>
>> By the time I got to see it, the cat was glowing literally orange
>
> When did Lada ever fit cats ?
>
>


In Canada in the '80s.


--
TeGGeR®

I've just had this exact thing with my VW. Had to have a brand new
exhaust system and the catalytic converter had completely crumbled, so
effectively the car couldn't breathe. I had severe loss of power
(couldn't go over 70) and it sounded like the exhaust was going.
Apparently I was lucky the car didn't catch light. Hope you've got a
wad of cash to hand...

TeGGeR® wrote:
> wrote in news:1157715455.446907.8530
> @d34g2000cwd.googlegroups.com:
>
> > TeGGeR® wrote:
> >
> >> I once saw this exact thing on an '80s Lada Riva (Russian 4WD).
> >
> >> By the time I got to see it, the cat was glowing literally orange
> >
> > When did Lada ever fit cats ?
> >
> >
>
>
> In Canada in the '80s.
>
>
> --
> TeGGeR®

sihen wrote:

Hi everyone just an update
Had the car checked at work luckly i work for bus company so thers lots
of mechinics about.
Pretty much every one was right the cat died.
Gotta do lots of overtime to get it fixed.
Thought about just putting a staight pipe on there but i far to
concerned about the environment to do that so looks like i gotta get
the p[ushbike out the shed.
Thanks for all the reply's
Si...
Bristol
England

sihen wrote:
> sihen wrote:
>
> Hi everyone just an update
> Had the car checked at work luckly i work for bus company so thers lots
> of mechinics about.
> Pretty much every one was right the cat died.
> Gotta do lots of overtime to get it fixed.
> Thought about just putting a staight pipe on there but i far to
> concerned about the environment to do that so looks like i gotta get
> the p[ushbike out the shed.
> Thanks for all the reply's
> Si...

Just gut the cat, it's toast anyway...

> Bristol
> England
>
Ulf

jeffcoslacker wrote:
> Ad absurdum per aspera Wrote:
>
>>or are running so horribly overrich that
>>a lot of fuel is actually burning within the exhaust manifold. I'd
>>actually consider having this one towed to a reputable mechanic.
>>
>>
>
>
> I have a problem with this...and I'm not trying to start a fight or
> imply that you don't know what you are talking about...because you
> obviously do...BUT..
>
> A rich mixture cools combustion. It CAN make the area near the exhaust
> port run somewhat hotter than normal due to continued burning after the
> exhaust stroke IF...there is a supply of oxygen available to the hot
> mixture inside the exhaust system.
>
> This is usually not the case, however. It would happen sometimes on the
> old early emissions control equipped motors that had active or passive
> air injection into the manifolds...

Most vehicles still have at least passive air aspiration systems. You
can't make a catalyst work without some added air in the exhaust stream.
Much LESS air is added now than in the days of big air pumps on
carbureted engines, but its still added.

> if you want to see a
> manifold turn red, an extremely LEAN mix is the way to go about it...

Or run with a severe misfire. A misfire causes perfectly-mixed
ready-to-burn air/fuel to be dumped into the exhaust plumbing. A dead
cylinder or two will melt down an exhaust system pretty easily, which is
why for 30 years now its been against recommended service procedure to
pull a spark plug wire, even briefly, for diagnostic purposes.



>
> Another thing...the cat. It gets hotter the more unburned fuel it has
> to digest. At a certain point, it becomes too much, and it will begin
> to overheat, glow, and the interior structures will begin to fall
> apart


Not without that oxygen you claim isn't available in an over-rich
mixture. A catalyst FACILITATES combustion, but it can't create
combustion without both fuel and oxygen to combine.

Steve Wrote:
> , which is
> why for 30 years now its been against recommended service procedure to
> pull a spark plug wire, even briefly, for diagnostic purposes.

Actually it's to keep raw HC out of the Cat, for the reason I explained
before.



>
> Not without that oxygen you claim isn't available in an over-rich
> mixture. A catalyst FACILITATES combustion, but it can't create
> combustion without both fuel and oxygen to combine.

There is no combustion occuring in the cat. If there is, it destroys
it, as I said. Check your understanding of a cat's job. You have some
wrong assumption going.

Also explain where this air is admitted to the exhaust stream. Haven't
seen an air pipe on a cat since the mid 90's...an OBD II system with
up- and downstream O2 sensors couldn't provide any useful info in an
open system with air being admitted post-combustion...


--
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jeffcoslacker Wrote:
> Actually it's to keep raw HC out of the Cat, for the reason I explained
> before.
>
>
>
>
>
> There is no combustion occuring in the cat. If there is, it destroys
> it, as I said. Check your understanding of a cat's job. You have some
> wrong assumption going.
>
> Also explain where this air is admitted to the exhaust stream. Haven't
> seen an air pipe on a cat since the mid 90's...an OBD II system with
> up- and downstream O2 sensors couldn't provide any useful info in an
> open system with air being admitted post-combustion...


OXYGEN STORAGE
In order to oxidize CO and HC, the catalytic converter also has the
capability of storing the oxygen from the exhaust gas steam, usually
when the air fuel ratio goes lean. When insufficient oxygen is
available from the exhaust stream the stored oxygen is released and
consumed. This happens either when oxygen derived from NOx reduction is
unavailable or certain maneuvers such as hard acceleration enrich the
mixture beyond the ability of the converter to compensate.


--
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jeffcoslacker > wrote in
:

>
> Steve Wrote:
>> , which is
>> why for 30 years now its been against recommended service procedure to
>> pull a spark plug wire, even briefly, for diagnostic purposes.
>
> Actually it's to keep raw HC out of the Cat, for the reason I explained
> before.
>
>
>
>>
>> Not without that oxygen you claim isn't available in an over-rich
>> mixture. A catalyst FACILITATES combustion, but it can't create
>> combustion without both fuel and oxygen to combine.
>
> There is no combustion occuring in the cat. If there is, it destroys
> it, as I said. Check your understanding of a cat's job. You have some
> wrong assumption going.
>
> Also explain where this air is admitted to the exhaust stream. Haven't
> seen an air pipe on a cat since the mid 90's...an OBD II system with
> up- and downstream O2 sensors couldn't provide any useful info in an
> open system with air being admitted post-combustion...
>

If you would bother to check almost every eng still has a air pump.
and air passages are intragel with the head, not external. air is still
added post combustion as has been since the adoption of cats.
>



--
Thunder Snake #9
"Protect" your rights or "lose" them.

Kevin Bottorff Wrote:
> If you would bother to check almost every eng still has a air pump.
> and air passages are intragel with the head, not external. air is still
> added post combustion as has been since the adoption of cats.
> .

Really? As a state liscenced emissions tech since 1991, that's the
first I've heard of it, outside of the active and passive systems I've
already described, which are obsolete now.

Where is this pump located? I'll have to go check it out.

Wanna explain how a closed loop feedback system with multiple o2
sensors can create an accurate reading of o2 levels in combustion gases
if external air is admitted before sensing? I'm fascinated.

Please quote some sources, because I've been looking since you posted
this, and can't find a thing about it...


--
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Well, one of the things that's limited us to handwaving in this
diagnosis is that the original poster didn't really specify anything
about make, model, year, engine...

Leaks can also admit external air where and when the designers didn't
mean to, under some conditions.

Anyway, he and friends have evidently established internal clogment of
the cat as the problem. So... what caused that? Did it just get old
and/or rusty and collapse internally, or was this a meltdown from
excess fuel? I think that car needs more diagnosis before it gets a
clean bill of health... and in particular, throwing a new cat into a
car that tends to plug the things by puking oil and/or macroscopic
amounts of unburned gas into them could be an expensive waste of parts.


Cheers,
--Joe