Oil burning engines enjoy lower rates of wear?
Christopher Tidy
A question for the engine experts. Someone commented to me recently that
engines which intentionally burn significant quantities of their
lubricating oil enjoy a reduced rate of cylinder wear as more oil is
available at the upper end of the cylinder. Simple question: it makes
sense, but is it an established fact? Do designers sometimes design
engines to burn oil for this reason?
Just curious.
Chris
Jim Stewart
I don't have a clue as to whether it's
an established fact, but I could probably
find out for you. A member of my model
engine club acually designs engines and
did a great tech talk on the subject of
piston rings. He didn't mention this
issue.
My personal opinion is that anything but
a tiny bit of oil past the oil ring will
cause eventual coking and sticking of the
compression rings.
Christopher Tidy
Well, if you see your friend please do ask. I was told that the
Rolls-Royce B60 engine was designed to burn oil for the purpose of wear
preventation.
Chris
Eric R Snow
This seems to me to be false. I suppose if the engine is designed to
actually burn the oil so that it doesn't carbon up the engine it might
work. But all the gasoline engines I've seen that burned oil because
it was leaking past either the oil rings or the valve guides suffered
from carbon build up in the combustion chamber. This leads to higher
compression which then leads to detonation. The carbon is also
abrasive so the cylinder wear is accelerated. The ringes also get
coked up so that they stick and no longer seal as well. This of course
leads to more oil consumption and increased blow by. The combustion
products in the oil cause corrosive compounds to form which leads to
accelerated wear of the engine parts bathed in oil. Of course I am
only familiar with perhaps 1/10000 of 1% of engines made so it's a
distinct possibility that someone designed and built an engine to work
this way but it seems unlikely.
ERS
clareatsnyder.on.ca
wrote:
Not to mention that the oil reduces the effective octane rating of the
fuel - just when higher octane is required to combat the higher
compresssion ratio and cyl temps caused by the carbon buildup from the
burning oil - - - - - .
--
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Chris D
Doubt it. Even if you designed an engine that let oil past the oil
control ring it probably wouldn't reduce wear. The ring area of the
piston is typically smaller diameter so it doesn't contact the cylinder
anyway. A small amount of oil gets by the control ring on all engines
but not enough to where you could say it's burning it. Modern materials
that comprise cylinder walls and rings live with this very small
quantity of oil.
The best thing that's happened to piston engines is the advent of
electronic fuel injection. Carb engines wash oil off the cylinder walls
on start up because chokes dump too much fuel. Fuel injection controls
this better hence engines are lasting longer. A carb engine typically
goes 100K, fuel injection over 200K.
Robert Swinney
Bob Swinney
"Chris D" <nom...@nospam.com> wrote in message
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Anthony
news:449B35FB...@cantabgold.net:
I've never heard of one, except a 2-stroke and that isn't for reduced
wear in the upper cylinder area. The amount of oil left in the
combustion chamber area is very precisely calculated and controlled.
(This is the reason engine manufacturers have a very specific
cross-hatch call-out on the cylinder bore.) You want just enough oil to
lubricate the rings and only that much. Even on the pistons, there is a
very specific surface finish which is calculated by the actual volume of
oil required to be retained in the microscopic grooves machined into the
part for lubrication. Adding oil to the upper combustion chamber causes
all kinds of ills, including increased NOx emmisions, hampered
flame-front propagation, excessive unburned fuel, carbon build-up
resulting in disturbed charge flow, pre-detonation, hot spots, scoring,
flaking, reduced valve sealing capabilities and can lead to piston burn
and/or valve or valve seat burn, stuck compression rings and other
problems.
--
Anthony
You can't 'idiot proof' anything....every time you try, they just make
better idiots.
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wayne mak
oil consumption, they burn some oil and these days how often do people even
check.
http://www.usatoday.com/money/autos/2006-06-02-altima_x.htm?csp=34
"Anthony" <tonyt...@hotmail.com> wrote in message
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jtaylor
"Christopher Tidy" <cdt22...@cantabgold.net> wrote in message
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I drove a 220D for about 10 miles at 50-ish after the oil plug fell out.
Only siezed when I slowed for a left turn. Repair man (after saying "ooops,
that's why I have insurance") rebuilt engine for free and said main bearings
and rings were replaced but cylinders and pistons were fine.
Oil-burning engines of the diesel variety are not designed to burn oil
specifically for longevity - it's a bonus.
Mark Rand
You're lucky (said he who drove a 2 litre diesel Peugeot for 10 miles without
water and suffered no harm other than the one hour delay before being brave
enough to put some water in without cracking the block).
Mark Rand
RTFM
Christopher Tidy
interesting thoughts. I might try to get hold of a Rolls-Royce B60
engine manual and see if it mentions intentional oil burning.
Best wishes,
Chris
clareatsnyder.on.ca
Just an asside on Deisels and oil consumption. Most deisels are NOT
air throttled, and if the engine starts to burn oil, the power output
goes up, in direct proportion to the amount of "extra fuel" being
supplied. It can become impossible to shut down a deisel engine with
an oil burning problem, and a BAD oi burning problem can produce HUGE
amounts of power which, if the engine "gets away" can destroy itself
in very short order. I've seen several pairs of coveralls sucked into
an intake in an attempt to stop the airflow and prevent an engine from
"grenading" itself due to one broken ring land on one piston.