2-stroke diesel is the (near) future?

Guess why?
*Duh* Pollution laws, and no need for the power to weight
requirements of Aviation! Duh... whats that got to do with this topic?
Other than to show that 2 stroke Compression ignition engines are a
proven concept?

wingsnaprop wrote:

Guess why?
*Duh* Pollution laws, and no need for the power to weight
requirements of Aviation! Duh... whats that got to do with this topic?
Other than to show that 2 stroke Compression ignition engines are a
proven concept?


As already stated, 2-stroke diesels really don't have a power-to-weight
advantage over 4-strokes. They still have to have a camshaft and
exhaust valves (they aren't like weed whacker engines, you know), so
they don't save that weight. Plus they have to have a blower for
scavenge air. The only area where they save weight is in that the
connecting rod and crank can be lighter, and that only helps offset the
added weight of the blower.

"Steve" wrote

As already stated, 2-stroke diesels really don't have a power-to-weight
advantage over 4-strokes. They still have to have a camshaft and
exhaust valves (they aren't like weed whacker engines, you know), so
they don't save that weight. Plus they have to have a blower for
scavenge air. The only area where they save weight is in that the
connecting rod and crank can be lighter, and that only helps offset the
added weight of the blower.

How about the fact that they have power pulses in each revolution? They
could possibly have half the displacement, and still get the same power, (or
close to it) with less weight than the double displacement 4 cycle. Yes,
the blower weight is added, but it is nice to make good power, way up there.
--
Jim in NC

Morgans wrote:

"Steve" wrote


As already stated, 2-stroke diesels really don't have a power-to-weight
advantage over 4-strokes. They still have to have a camshaft and
exhaust valves (they aren't like weed whacker engines, you know), so
they don't save that weight. Plus they have to have a blower for
scavenge air. The only area where they save weight is in that the
connecting rod and crank can be lighter, and that only helps offset the
added weight of the blower.


How about the fact that they have power pulses in each revolution? They
could possibly have half the displacement, and still get the same power, (or
close to it) with less weight than the double displacement 4 cycle. Yes,
the blower weight is added, but it is nice to make good power, way up there.


The blower also takes away a significant chunk of crankshaft power. The
blower has to do the same net work as those "non power" strokes in a
4-cycle diesel because its doing the same job- expelling burnt mixture
and bringing in fresh air. You can't get something for nothing.

This is all old-hat. 2-stroke diesels have been in widespread use since
Winton developed the basic foundation for what became both the EMD and
Detroit Diesel 2-stroke engine architecture back in the 1920s. 2-strokes
became very simple to service and reliable, but they rarely won on
either fuel efficiency or total power output per unit weight. That's why
you find 2-strokes in locomotives and ships where weight doesn't matter
(or is a benefit), but they all but disappeared from on-road
applications by the end of the 1970s and DID completely disappear by the
turn of the century.

Steve wrote:
Morgans wrote:

"Steve" wrote


As already stated, 2-stroke diesels really don't have a
power-to-weight
advantage over 4-strokes. They still have to have a camshaft and
exhaust valves (they aren't like weed whacker engines, you know),
so
they don't save that weight. Plus they have to have a blower for
scavenge air. The only area where they save weight is in that the
connecting rod and crank can be lighter, and that only helps offset
the
added weight of the blower.


How about the fact that they have power pulses in each revolution?
They
could possibly have half the displacement, and still get the same
power, (or
close to it) with less weight than the double displacement 4 cycle.
Yes,
the blower weight is added, but it is nice to make good power, way
up there.


The blower also takes away a significant chunk of crankshaft power.
The
blower has to do the same net work as those "non power" strokes in a
4-cycle diesel because its doing the same job- expelling burnt
mixture
and bringing in fresh air. You can't get something for nothing.

This is all old-hat. 2-stroke diesels have been in widespread use
since
Winton developed the basic foundation for what became both the EMD
and
Detroit Diesel 2-stroke engine architecture back in the 1920s.
2-strokes
became very simple to service and reliable, but they rarely won on
either fuel efficiency or total power output per unit weight. That's
why
you find 2-strokes in locomotives and ships where weight doesn't
matter
(or is a benefit), but they all but disappeared from on-road
applications by the end of the 1970s and DID completely disappear by
the
turn of the century.

I would have agreed at the start of this thread, but the two stroke
desiel does not have to be the same as the old locomotive desiels. The
blower is not needed if the crankcase is used to pump fuel/air mixture.

Sport Pilot wrote:

Steve wrote:

Morgans wrote:


"Steve" wrote



As already stated, 2-stroke diesels really don't have a

power-to-weight

advantage over 4-strokes. They still have to have a camshaft and
exhaust valves (they aren't like weed whacker engines, you know),

so

they don't save that weight. Plus they have to have a blower for
scavenge air. The only area where they save weight is in that the
connecting rod and crank can be lighter, and that only helps offset

the

added weight of the blower.


How about the fact that they have power pulses in each revolution?

They

could possibly have half the displacement, and still get the same

power, (or

close to it) with less weight than the double displacement 4 cycle.

Yes,

the blower weight is added, but it is nice to make good power, way

up there.


The blower also takes away a significant chunk of crankshaft power.

The

blower has to do the same net work as those "non power" strokes in a
4-cycle diesel because its doing the same job- expelling burnt

mixture

and bringing in fresh air. You can't get something for nothing.

This is all old-hat. 2-stroke diesels have been in widespread use

since

Winton developed the basic foundation for what became both the EMD

and

Detroit Diesel 2-stroke engine architecture back in the 1920s.

2-strokes

became very simple to service and reliable, but they rarely won on
either fuel efficiency or total power output per unit weight. That's

why

you find 2-strokes in locomotives and ships where weight doesn't

matter

(or is a benefit), but they all but disappeared from on-road
applications by the end of the 1970s and DID completely disappear by

the

turn of the century.


I would have agreed at the start of this thread, but the two stroke
desiel does not have to be the same as the old locomotive desiels. The
blower is not needed if the crankcase is used to pump fuel/air mixture.


You're describing a weed-whacker engine, not a 2-stroke Diesel. Good for
cheap manufacture and relatively light total weight, but at the expense
of a very narrow power band, terrible efficiency, terrible emissions,
and except at the peak of the power band, terrible power/weight ratio in
spite of being lightweight.

Steve wrote:
wingsnaprop wrote:

Guess why?
*Duh* Pollution laws, and no need for the power to weight
requirements of Aviation! Duh... whats that got to do with this
topic?
Other than to show that 2 stroke Compression ignition engines are a
proven concept?


As already stated, 2-stroke diesels really don't have a
power-to-weight
advantage over 4-strokes. They still have to have a camshaft and
exhaust valves (they aren't like weed whacker engines, you know), so
they don't save that weight. Plus they have to have a blower for
scavenge air. The only area where they save weight is in that the
connecting rod and crank can be lighter, and that only helps offset
the
added weight of the blower.


I said something similar, but I don't know that a desiel has to have
the valve, as the old locomotive two strokes. Could it not be ported,
as the two stroke spark engines? The fuel is already oily so if the
bearings are sealed ball bearings, you may not have to add oil to the
fuel.

Not saying this is preferable, just possible.

Sorry about the two similar posts. I didn't think the first "took".

Sport Pilot wrote:

Steve wrote:

wingsnaprop wrote:


Guess why?
*Duh* Pollution laws, and no need for the power to weight
requirements of Aviation! Duh... whats that got to do with this

topic?

Other than to show that 2 stroke Compression ignition engines are a
proven concept?


As already stated, 2-stroke diesels really don't have a

power-to-weight

advantage over 4-strokes. They still have to have a camshaft and
exhaust valves (they aren't like weed whacker engines, you know), so
they don't save that weight. Plus they have to have a blower for
scavenge air. The only area where they save weight is in that the
connecting rod and crank can be lighter, and that only helps offset

the

added weight of the blower.



I said something similar, but I don't know that a desiel has to have
the valve, as the old locomotive two strokes. Could it not be ported,
as the two stroke spark engines?

In order to scavenge the cylinders properly, the inlet ports need to be
at the bottom of the cylinder and exhaust valves have to be located at
the top. The only viable alternative is the opposed piston engine (ala
Fairbanks-Morse) in which one piston uncovers an inlet port array and
the other uncovers the exhaust ports. But then you have the weight of an
additional CRANKSHAFT, without any increase in output power!

The fuel is already oily so if the
bearings are sealed ball bearings, you may not have to add oil to the
fuel.

I think you're confusing a weed-whacker/outboard motor type 2-stroke
with a 2-stroke diesel. A 2-stroke diesel has a closed crankcase just
like a 4-stroke.