Re: Re: Red Hot Exhaust / Melted Catalytic Converter

["content22207 <brobertson@xxxx>" <brobertson@xxxx>]

Oh boy -- test driving a new modem in my friend's computer just in
time for a disagreement...

Lean fuel mixtures burn hotter than rich ones. What do you do to
increase temperature of a welding torch? Increase the oxygen. What
happens when you put too much LP to your grill? The flame turns orange
(cool). You'll know when you have unburned fuel in the exhaust system
by the inevitable muffler fart or explosion, depending on amount (this
is what happens on loose engines that continue to rotate briefly after
ignition is turned off).

BTW: my cat melted when the fuel pickup was totally stopped up -- an
ultimate lean condition.

And yes, my firefighter friend just confirmed you can indeed put out a
fire with LIQUID gasoline (it's the oxygenated vapors that burn).

Bill Robertson
#5939


PS: After further conversation w/ fire department buddy, better example of
lean vs. rich fuel mixture would be soldering torch. Only variable w/
plumber's torch is propane (uses outside atmosphere for oxygen just
like a car). Welder's torch is a closed system.

Apologies...



>--- In dmcnews@xxxxxxxxxxxxxxx, "David Teitelbaum <jtrealty@xxxx>"
<jtrealty@xxxx> wrote:
> A glowing catalytic converter is a sign of an over-rich condition with 
> unburned hydrocarbons in the exhaust. When these unburned hydrocarbons 
> enter the catalytic converter (which under normal conditions runs 
> 1200-1500 degrees) they burn which causes the temperature of the 
> coverter to go over 2000 degrees. It can get hot enough to fuse the 
> matrix of platinum pellets and stainless gratings which can cause the 
> converter to become "plugged up" or restrict the flow of exhaust 
> gases. This is most noticeable as a lack of power at high RPM's.
> Besides an out of adjustment fuel system one of the more common 
> causes is a misfiring cylinder caused by a bad ignition wire or spark 
> plug. Since the fuel isn't consumed in the cylinder it gets into the 
> exhaust where it burns inside the catalytic converter. Short periods 
> of this don't always cause permanant damage. Over longer times it will 
> distort the exhaust system, damage the catalytic converter, 
> contaminate the O2 sensor, melt nearby plastic and fiberglass, and 
> possibly set the car on fire. Fuel cools, at least unless it is being 
> oxidized! I wouldn't try putting out a fire by throwing cool fuel on 
> it!!!!! 
> David Teitelbaum
> vin 10757
> 
> 
> --- In dmcnews@xxxxxxxxxxxxxxx, "content22207 <brobertson@xxxx>" 
> <brobertson@xxxx> wrote:
> > Am on Xmas vacation, so this is first time I've seen list all 
> week...
> > 
> > It is indeed possible to melt the guts of a honeycomb style 
> catalytic
> > converter. Not sure why (stuff has consistency of ceramic), but I 
> did
> > so when my car ran too LEAN (remember guys: fuel cools. Until Martin
> > G's PRV man diagnosed my re-tuned, hence over-advanced engine -- 
> still
> > getting used to life without a carburetor -- was so rich I could
> > actually hold exhaust tips in my hands). Telltale sign of stopped up
> > converter is glowing exhaust AFTER the the thing. I think it's heat
> > from added resistance.
> > 
> > Do you live in an area with emissions testing? You'd be amazed how
> > much restriction a converter puts on exhaust flow. And even when
> > properly functioning is unreasonably hot.
> > 
> > Bill Robertson
> > #5939