This is long I am afraid.
Bob Donahue:
I don't think I ever saw an answer to your questions, so
here goes.
<<<snip>>>
I read some where that the excessive wear that occurs when
you start an
engine is not due to a lack of lubrication. The article
claimed the real
problem is that a stone cold engine makes water instead of
water vapor.
(Burning a hydrocarbons always produces some H2O.) Some
owner's manuals
(including my MG's) seem to support this opinion.
Here's a quote from my MGB owner's manual:
"Warming up: Research has proved that the practice of
warming up an engine
by allowing it to idle slowly is definitely harmful. The
correct procedure
is to let the engine run fairly fast, approximately 1,000
r.p.m., so that it
attains its correct working temperature as quickly as
possible. Allowing the
engine to work slowly in a cold state leads to excessive
cylinder wear, and
far less damage is done by driving the car straight on to
the road from cold
than by letting the engine idle slowly in the garage."
Has anyone else hear this cold engine / water theory?
<<<snip>>>
There's several things to consider.
A) On initial starting before the fuel fires you've got wear
not only on the rings/bores but on the bearings. If you're
using a dry sump with an electrical scavenge pump that
doesn't help as the engine pump pressurizes the engines
system.
The best method of starting up from a long lay up is to
remove the plugs and crank until oil pressure shows, Then
replace the plugs and fire up the engine.
An alternative with the MGA and earlier, is to leave the
ignition key off and just crank until you get oil pressure
IF you've got a good battery. This works very nicely if the
car has sat a while and fuel has evaporated from the carbs.
Then there's little worry of flooding the engine.
B) After the engine fires there is some condensation of the
water from combustion on the cold parts, but this can't last
more than a few seconds. Remember, there's fire and heat in
the engine every time a cylinder fires. The warm area may
only be on the surface, but it is warm.
C) The main culprit is the choke. Stangler in TD jargon.
When the strangler is on not all of the fuel is burned and
it washes down the cylinder walls because the engine is cold
and not all of the fuel vaporizes. Gasoline will thin oil.
Water and oil don't mix. You probably know that if the
engine RPM's are above 2000 the engine will usually run
without the choke when it's just about stone cold. The only
way you can achieve a 2000 rpm engine speed and the choke
off is to drive the TD.
D) The harder an engine works the more heat it generates.
The more heat it generates the the faster it warms up. Want
to make the engine work harder than idling? Drive the car
at moderate speeds as soon as the oil pressure comes up.
Don't "cob it" as that just throws more fuel in to wash the
cylinders down.
E) Short trips where the engine is shut down before it
warms up is tough on an engine too. The engine doesn't get
hot enough to vaporize the gas and water which has mixed
with the oil.
I have a Datsun 240Z. It's got SU licensed carbs on it very
similar to HSs. My winter procedure was to start the
engine, THEN fasten the seat belt. This gives a few seconds
for the oil pressure to come up. I moderately drive off and
as soon as the car is over 20 mph and in second gear off
goes the choke. You sometimes have to pull it back on some
depending on the temp, stops, or reduced speed.
<<<snip>>>
I know a few people who religiously wait for their engines
to warm up
idling, especially in the winter. Sounds like they may be
doing just the
opposite of what's good for the engine.
<<<snip>>>
That kind of procedure is very detrimental to the longevity
of an engine. Modern oils and fuel injection have helped
some, but it's still poor practice. They just never read
the owner's manual which is more like a book than a manual.
And don't get me started on all of the cautions and safety
warnings that you have to wade through!
What they really want is a warm car to get into. For that,
the least expensive partial solution is to install a core
plug heater in the engine block and use it even when the car
is in the garage. These warm the engine better than a lower
radiator hose heater and cost much less to operate. With a
lower radiator hose heater sometimes the heated water
doesn't flow right. And the thermostat at the top of the
engine is also closed. An extra option for a plugged in car
is to use a clock timer on the cord to the soft plug
heater. I set the timer to go off at 3 AM for a 7:30 leave
the home time.
A car in an attached insulated garage and plugged in warms
up very fast when driven. It takes just a few miles to get
heat into the cabin. Good old cardboard blocking 1/2 to 2/3
of the radiator is always helpful for faster warm-ups in the
winter regardless of whether the car's got thermostatic
fans. It works best in front of the radiator, not in front
of the grill as I've seen some. As the car moves the
blockage keeps the cold air from going through the radiator
and blowing on the engine. Just put a note on the dash to
remove the cardboard in March!
--
Blake
MG TD
MGA twin cam
Home page: http://members.nvc.net/yd3/
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