Engine efficiency

[drmiller100]

Originally Posted by NeilBlanchard

At lower speeds rolling resistance is the majority of the load. .

And how do we calculate rolling resistance?

Can we agree rolling resistance is TOTALLY WASTED ENERGY (just like aero)????

I wish I could have a variable mass car. Then I could accelerate a light car, then drive along down the road with a light car, but then when it came time to coast I could have instantaneous perpetual motion energy to coast along.........

[drmiller100]

Originally Posted by pete c

I think extra weight can be helpful if your drive includes long not very steep declines where the extra weight keeps you at a high enough speed to avoid being run down.

If I sent you a bunch of free bubblegum would you try chewing it while walking????

[Frank Lee]

I'd like to give that a shot!

[Frank Lee]

Speaking of engine efficiency, I still don't get why the efficiency of the world's most efficient ICE, a huge MAN two-stroke diesel, is not scale-down-able.

[user removed]

Some of it would be as long as its RPM was in a narrow range.

regards
Mech

[merccom]

Originally Posted by Frank Lee

Speaking of engine efficiency, I still don't get why the efficiency of the world's most efficient ICE, a huge MAN two-stroke diesel, is not scale-down-able.

you can scale it down, the problem is making useable power in a vehicle size package.

remember that thing only spins about one hundred rpm. if you scale it down to 18wheeler engine size you'll only be making 20 or so horsepower

figure your average detroit makes around 1100 pounds of torque at 1200rpm

if you take that same 1100 ft/lbs and drop it back to 100rpm

you have 1100ft/lbs * 100rpm = 110,000/ 5250 = 20.95hp

so you have a road tractor engine that puts out 21 hp.

it would make an awesome stationary engine for a small generator.

[Frank Lee]

The MAN RTA96-C:
38" bore x 98" stroke
111,143 CID for one cylinder
7780 HP @ 102 rpm for one cylinder
1,666 mean piston speed
50% efficiency
****************
Wouldn't a 3.8" x 9.8", 111.14 CID one lunger at 1,020 rpm (same 1,666 piston speed) also be 50% efficient and put out how much hp and torque?

[maxc]

Originally Posted by Frank Lee

Speaking of engine efficiency, I still don't get why the efficiency of the world's most efficient ICE, a huge MAN two-stroke diesel, is not scale-down-able.

It's called "local taxes"!

[mort]

Originally Posted by Frank Lee

Speaking of engine efficiency, I still don't get why the efficiency of the world's most efficient ICE, a huge MAN two-stroke diesel, is not scale-down-able.

Hi Frank Lee,
For a start, the displacement, a bunch of cylinders: volume is like pi * r**2 * h, so displacement is proportional to the square of the bore. Where does the heat go? Some pushes down on the piston, some goes out the exhaust. And a bunch goes through the cylinder walls to the radiator. So how do cylinder walls scale? Like the area of the cylinder: 2 * pi * r * h. So the cylinder wall area scales linearly with the cylinder radius.
OK?
-mort

[pete c]

Originally Posted by drmiller100

If I sent you a bunch of free bubblegum would you try chewing it while walking????

Sure. I'd prefer chocolate though.