Hi Bill Eastman!!
On Fri, 13 Jun 1997, Bill Eastman wrote:
> optimal. It runs great with no stumbles or misses except at idle. When
> cool, it idles great but once it is totaly warm it has a slightly lumpy
Yes, that's an accurate description of the sound of an engine running
rich, as opposed to the "splashy", irregular sound of a lean mixture.
> idle and long term idling in hot weather requires that I "clear the carbs"
What you are actually doing is "clearing" the build-up of fuel from the
manifold, not the carbs.
> occasionally or it will slow below 500 rpm (it hasn't quit yet). It is
> funny that all of the tech manuals that I have read recommend clearing the
> carbs occasionally during tuning. The only reason to do this would be that
> the carbs are rich or drift to rich on extended idle or low rpm operation.
Yes, when you do that, it clears the excess fuel from the walls of the
manifold, and allows you to obtain a true reading as you work. On the
pre-pollution carbs, I find it easier to start with a lean mixture, and
tune towards the proper ratio; whereas on the pollution carbs, I just do
as the engine compartment says. Remember, I MUST pass a pollution test
BEFORE I can obtain my plates and insurance, so I don't get inventive.
> The worst thing that you can do to an engine is let it go lean at full
> power. This will burn a hole in a piston fairly quickly. Other than that,
> Aircraft engines, in fact, spend a lot of time running rich. Listen to/
Yes, they do. Take-off, and climb to altitude will be done from 3/4 to
full throttle, so if you want to climb to 10k feet at 1k ft/min, then
you are destined to be at full/3/4 throttle for app 12 to 13 minutes.
Not too many places outside of Nevada where you can run wide open for
that length of time in your car...
> smell a small plane at idle and takeoff. You set the mixture to full rich
> and there is plenty of fuel around. The reason for full rich at idle is
> that the engine doesn't cool well on the ground and a rich mixture lowers
> temperatures. A friend of mine flies a turbo Navajo and he says that the
And the reason for full rich at take-off is because 11.5 to one gives
the most POWER, while 14.? to one gives the best milage at cruise.
NOBODY runs full rich at cruise... unless you screw up.
> which spend a lot of time at or near the rich limit, have a recommended TBO
> (time between overhauls) of 2000 hours which is about equal to 100k miles
> on a car. The FAA isn't too worried about cylinder washdown by rich idle
That's because an aircraft engine spends far more of its lifetime
running at cruise rpm than it does at idle, as opposed to a car having
to deal with traffic. Remember that your carb AUTOMATICALLY enrichens
the mixture, and leans it out, so if you start out rich, you end up
going richer than the 11.5 to one you need for max. power under load
> nose isn't as good as it used to be but I suspect that the formulation of
> new gasolines don't smell the same when partially burned as the fuel that
> we grew up with. My car has more of an industrial cleanser smelling
> exhaust at idle.
Yup, you're right!! The new gas smells weird compared to the older
formulations.
> I agree that a 160F thermostat is too cool. I have been meaning to buy a
> 180F t-stat but I keep forgetting. Maybe once the finance department
^^^^^^^^^^^^^^^^^
Definite indicator of old fart status!! Congrats are in order!!
TTUL8r, Kirk Cowen (who's been told by his ip "it's not a car yer
driving, it's time to cut back to 3/4 throttle
and let it cool down".)
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