The Herr Family wrote:
>
> James,
> Catalytic converters do work well on new engines. But do you remember the
> cars of the 70's. Before the grand days of computer controlled engines,
> fuel injection
> and distributorless ignition, cars were slapped with lean burn carbs, low
> compression
> and a catalytic converter. They ran terrible, had no power and after
> 30,000-40,000 miles
> were producting emissions just like older cars.
Some truth to this... converter plugging in such older cars was
considerably more common than today, but that had as much to do with old
cars still having some bore-washing from occasionally rich mixtures
(during choke operation, for example), and therefore, cylinder wear
problems, which increased the amount of oil passed out of the cylinders
and into the converter. Accurate fuel injection has minimized that
problem, with the added bonus of making engines last considerably
longer.
> For cars built in the 70's, where they
> are subject to emissions
> and won't pass the test, you possibly might consider such modifications.
> British Car Magazine
> featured an MGB converted to fuel injection and running a cat.
Regarding catalytic converters, this conversion did not feature one, as
I recall. Or, at least, dispensed with the O2 sensor to force the system
into closed-loop operation, for the purposes of power, not emissions. I
thought the installation described (I received a text-only version)
sounded a bit clunky and inelegant, as I have mentioned here previously.
> But for a
> car built in 1963, no
> emissions are required. You probably would just make the car run badly, and
> worse if you do not
> mount the cat. in a proper location, you might set the car on fire from the
> heat. Cat. converters glow
> red from the chemical reaction and with an improper fuel/air ratio, could
> over heat.
This is quite true. I've possibly mentioned this before, but for the
sake of the new folks, I'll pass it on again. In the early `80s, I
worked for a Toyota dealership in west Florida. A two-year-old pickup
was given to a young kid with not much experience for a tune-up, with
instructions that the engine had a miss. As with several of the
mechanics in the shop, he had no experience with an engine oscilloscope,
but part of a standard tune-up was electronic diagnosis, so he changed
the plugs and the air filter and hooked up the scope. Couldn't read it,
but he did hook it up. <g> Then sent the pickup out with the advisory
that a tune-up didn't fix the problem, and it might be something else.
The irony here (there's always irony in such instances <g>) is that this
same kid was walking out of a grocery store with a couple of cases of
beer for a weekend party, and, directly ahead of him was the pickup he'd
worked on two weeks prior, with the engine running while the owner went
into the same store. As he stepped down from the curb onto the parking
lot, the truck burst into flames. I think it was at that point that he
recognized it as the truck he'd worked on. <g> After the fire department
doused the flames and it cooled off a bit, it was towed into our shop,
with the interior of the cab looking very much like a Salvador Dali
painting, i.e., full of melted, dripping miscellany. <g> It was carted
off to the body shop and repaired. After two or three weeks, the pickup
was returned to us to replace the catalytic converter, which had
exploded.
Further irony--who got the converter repair job? Yup. The same kid. He
replaces the converter, hooks up the pipes, and starts it. Same miss in
the engine. By this time, he is a bit nervous about working on this
truck and asked for advice. "d'ya think I mighta done something to it to
cause this?," he asked. What did you do to it? "Tune-up." Why? "It had a
miss." Had to tell him that it might have been because of something he
didn't do. So, we hooked up the scope and I asked him what he saw. "To
tell you the truth, I really don't know how to use this thing, but they
told me I had to." Okay, put the thing in parade mode. He pushes the
button. Two spark traces on a four-cylinder engine. What's wrong with
this picture? <g> Monster crack in the cap between cylinders three and
four and ground. No spark whatsoever in two cylinders, which meant that
50% of the fuel going into the engine was going out of the engine
unburned and into the converter. Put a new distributor cap on it, and
the miss was gone, and the kid's face showed more relief than that of an
ax murderer with a reprieve.
The reminder here is that catalysis is almost invariably a process
driven by heat. The hotter the catalyst, the more efficient is the
process. The more efficient the process, the more heat produced. The
multiplication of those factors results in something described as
thermal runaway. The only control on a catalytic converter is the amount
of fuel delivered to it. A new converter attached to a tired,
environmentally dirty engine is a problem waiting to happen.
Cheers.
--
My other Triumph doesn't run, either....
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