50% Fuel to energy conversion 2 stroke
 

The Wartsila-Sulzer RTA96-C turbocharged two-stroke diesel engine is the most powerful and most efficient prime-mover in the world today. The Aioi Works of Japan's Diesel United, Ltd built the first engines and is where some of these pictures were taken.

It is available in 6 through 14 cylinder versions, all are inline engines. These engines were designed primarily for very large container ships. Ship owners like a single engine/single propeller design and the new generation of larger container ships needed a bigger engine to propel them.

The cylinder bore is just under 38" and the stroke is just over 98". Each cylinder displaces 111,143 cubic inches (1820 liters) and produces 7780 horsepower. Total displacement comes out to 1,556,002 cubic inches (25,480 liters) for the fourteen cylinder version.
Some facts on the 14 cylinder version:
Total engine weight: 2300 tons (The crankshaft alone weighs 300 tons.)
Length: 89 feet
Height: 44 feet
Maximum power: 108,920 hp at 102 rpm
Maximum torque: 5,608,312 lb/ft at 102rpm

Fuel consumption at maximum power is 0.278 lbs per hp per hour (Brake Specific Fuel Consumption). Fuel consumption at maximum economy is 0.260 lbs/hp/hour. At maximum economy the engine exceeds 50% thermal efficiency. That is, more than 50% of the energy in the fuel in converted to motion.
For comparison, most automotive and small aircraft engines have BSFC figures in the 0.40-0.60 lbs/hp/hr range and 25-30% thermal efficiency range.

Even at its most efficient power setting, the big 14 consumes 1,660 gallons of heavy fuel oil per hour.

https://people.bath.ac.uk/ccsshb/12cyl/

We just need one in a 1L version.

The main reason for the efficiency of this engine is an extrememly low surface area to displacement ratio. The low ratio is caused by the huge cylinders. Check out this spreadsheet:

1 liter 1 cyl 1 liter 4 cylinder Sulzer
bore 10.8383 6.83 96.52 cm
stroke 10.8383 6.83 248.92 cm
volume per cylinder 1000 250 1821310 cm3
area per cylinder 185 73 14634 cm2
number of cylinders 1 4 1
surface area per liter 0.18 0.29 0.01 cm2

A 1 liter four cylinder engine has 29 times higher surface area per liter than the Sulzer engine! Too much heat leaks out of the cylinders during the power stroke andf reduces efficiency in small engines.

A 1 liter engine can't attain such a good ratio.

However, if manufacturers want to build a 1 liter engine with the lowest possible surface area, it would be a 1 cylinder engine with 108 mm bore and stroke. for best efficicny, there are other considerations, such as achievable compression ratio, that would favor building a slightly smaller bore and longer stroke, say 105 by 115 mm.

But, all other things being equal, a one cylinder car will get the best mileage for a given engine displacement.

They shake too much so it has to be a three cylinder to attain the most reasonable balance . . . why the car makers keep building 4 cylinders I DO NOT KNOW!

Yup, a one cylinder is certainly not a smooth engine. But an opposed twin is.... Just ask a BMW. An opposed twin would be reasonably smooth, and would get better mileage than a similar four or three.

I'm partial to 3 bangers. I have Triumph triple 955i. Love the torque, love the sound. I just thought the article was cool. That's why I posted it.

You can get an old Lister diesel with a big stroke. One of these can run a generator and heat your house on waste heat running on used grease.

I want one of those 2300 ton engines for my Suzuki Swift! Think I would have to beef up the suspension?

The 3 cylinder Metro engine is not as smooth as the 4 cylinder. I had a 3 cylinder Subaru Justy that wasn't bad. It had a balancing shaft to smooth it out. I think the smoothest running (used to be common) engine is the straight 6.

Q

Someone double check my conversion, but I think my TDI's factory published max BSFC efficiency of 197g/KwH works out to 0.326 lb/hp hour, and significantly lower than the quote for most automotive engines, actually closer to the .26 than the .4.
I have absolutely no pretence that my mpg per ton comes anywhere near that of a container ship.

I decided to not get a BMW boxer specifically because of the side to side shake.
Both pistons stopped at TDC or BDC at the same time make the internal reciprocating mass of both pistons stop reciprocating for a moment, just the same as a single cylinder piston. But, instead of the cylinder pressure pushing the head, and attached cylinder and block up as the single piston is pushed down on a power stroke each 720 degrees, the opposed twin first pushes to the engine to the left as that left piston is fired to the right, and then 360 degrees later the engine is pushed right as the right piston is fired left. One pulse in one direction each two rotations, or two pulses, in opposite directions, each two rotations. I don't like getting slapped around, much less on both cheeks.

Instead I bought an 1100 Gold Wing, but even its flat four had a slight rotational shake as the rotating/reciprocating mass ratio changed throughout the crank's rotation (just like my Subarus). I later bought a 1500 Gold Wing with its six which eliminated that issue.

A six is smooth because it is two inline triples, there is a constant momentum to the reciprocating mass, as one piston is stationary at TDC or BDC, the alternate two are near their maximum stroke velocity. When one is at maximum, the other two are nearer to their slowest. A six is smoother than a triple because there are 6 power pulses spaced at 120 degrees rather than 3 at 240. But a triple can be inherently smooth as does not have the same inertial imbalance as a single, twin or four simply because all the reciprocating mass isn't stopped at some given instant.

BUT........ this is a fuel economy forum, not a vibration forum. My point is that a single cylinder will get better mileage than a three or four or six of equivalent displacement. And that an opposed twin reasonable compromise for a multicylinder.

Direct injection, Throttle body, Multi point fuel injection, single or multiple carburetor?
A single cylinder engine will have twice the pulsation of the air flow in the intake as the comparable displacement twin. The start-stop air flow will allow more opportunity for the fuel droplets to settle and coalesce on the wall as the air motion ceases for 630 degrees of the 720 four stroke crank rotation.
A multi cylinder engine will maintain a more constant air flow even if the direction of that air in a manifold changes from cylinder to cylinder.
This is less of a theoretical consideration with direct injection or multi-point injection with an injector dedicated to each cylinder, but in TBI or carburetor engines it needs to be aknowledged.
Internal friction will be less with a single than a twin or higher of same displacement since valves will still have some friction force against a camshaft, piston rings swept area won't diminish by the same factor their number increases, and on, so you do have a point there.
However, an opposed twin is less efficient than an inline twin, an opposed four is less so than an inline four when mining to recycling economy is considered. Materials and machining to make separate heads and cylinders are higher with opposed design engines. Added space requirements from not sharing cylinder walls also make for a more energy and material intensive manufacturing by requiring require a larger vehicle to enclose the engine.
V design multi cylinder engines can offset part of the space requirements, and offer other benefits, that may mitigate the manufacturing increases of two heads. Narrow angle V engines, if narrow enough, can use a single head for both cylinder banks.

HA!! I have a 1 liter Boxer 1978 actually a little under a liter and yeah I get about 60mpg with it at 75HP from 2 cylinders and twin carbs.

One of the big problems with flat engine designs is the crank shaft split case design and oil leaking into the cylinder heads when it stops. Centerstands are preferred on the boxers and the K bikes with their inline 3 and 4 cylinders have to heads on the right "high" side with the side stand for that reason. Everyong should remember the oil leaks from the old VW air cooled engines part from the expansion of the cylinders to the heads causing the pushrod tube to leak and some from the fact that the oil was flowing horizontally across seals that leaked instead of straight down.

As far as single cylinder engines are concerned Forgetaboutit they shake too much to be reliable except at low rpm and you will never get one to run smooth enough and produce enough power to push a car.

Three cylinder engines do run very smooth without counter balance shafts - my Geo was unbelievably smooth. My 80 rabbit would buzz so bad between 50 and 60mph you could not see out the inside rear view mirror. After driving teh Rabbit for 14 years I got my Geo and actually had my hearing improve from the quietness and smoothness of the Geo engine compared to the VW 4.

Now if you want to talk efficient then check out the linear stroke crankless electric power generators from Australia.

https://www.freepistonpower.com/fp3.htm
-----------------------------------------
Salient features of a 100kW FP3 module:

Size: 660x280x280mm
Mass: 100kg
Two-stroke operation
Integral charge compressor
Power Density: 1kW/kg; 2 kW/litre
Fuelled by Gasoline, Diesel (Bio, JP8), LPG, Ethanol, Hydrogen, etc.
Direct, high pressure fuel injection
Variable exhaust valve lift and timing
Variable compression ratio and stroke
Mechanical simplicity (software ‘replaces’ conventional con-rods, cam and crankshaft)
Readily scalable from 25 to 500kW output power
Efficiency 50%

The next generation IC engines will revert to the design of the WW1 era rotaries, which were not reciprocating engines. To better understand them google "animated engines gnome" Matt Keveney has a nice animation, which clearly demonstrates the effectiveness of the original aircraft rotary.

Forget all the pollution and emissions issues involved in the design they are all solveable with modern technology.

Reciprocation losses are the largest percentage of pumping losses. The piston begins at TDC accelerates to 90 degrees, decelerates to 180 accelerates again to 270 then decelerates again to TDC, with two complete revolutions to complete one 4 cycle combustion event per cylinder.

Thats 8 voilations of newtons law of inertia for every power stroke. I understand that this is not the sole cause of energy losses in current IC recip engines, but consider this. The roatry aircraft engine was responsible for tripling the speed records of aircraft from 1909 to 1913. A 753 CI rotary engine in 1913 produced 165 HP. The same year Mercedes Grand Prix engine was 1400 CI and ran at 2200RPM versus 1300 for the Rotary. The MB engine burned a quart of oil every 20 miles.

The original roatry engine is the basis of my future engine concept with many significant modifications;

Supercharged two stroke operation just like the topic engine alos with 3 to 1 bore to stroke ratio, designed to operate at low speed
Diesel combustion
Fuel injection
Closed loop oil system that also serves as cooling system
Elimination of all throttle control
Single intake and exhaust ports on center journal feeding reversed cylinders with pistons directly connected to outer rotating rim of the engine with no connecting rods
Adjustable crankshaft journal independent of engine support bearing that allows you to completely eliminate stroke with zero journal offset relative to rotating engine mass, which transforms engine into a free spinning flywheel for energy storage.
The free piston engines are improvements but they are still recip engines with greater vibration issues than conventional IC recips.
Due to narrow operating speed range, this will be much more adaptable to HCCI (homogenous charge compression ignition) hich basically is compression ignition using gasoline with lean burn ratios like a diesel, also adaptable to other fuels.

Nmame and engine that can transform itself into a flywheel eliminating 98% of all pumping losses and pulse and glide itself while propelling a car at a constant speed using a CVT but preferrably an IVT (infinitely variable transmission) with computer controls that are constantly changing the effecitve "gear" ratios as the flywheel storage speeds declines.

Using the flywheel for high initial acceleration combined with the engines power you now have a "hybrid" that needs no electric motor or batteries, with a system life expectancy greater than the best current non hybrid designs.

Mileage could exceed even current P&G levels because P&G incurs much higher aero drap at higher pulse max speeds.

Stephen Marius Balzer was a rotary engine poineer who worked with Langley on his failed aircraft attempt. He built a car with a rotary and donated it to the Smithsonian in 1899. A motorcycle called the Megola was built in Germany with a rotary engine inside the front wheel, a front wheel drive motorcycle no less.

Even if you removed the cylinder head and pushed the car to 60 MPH, staying in gear, the reciprocation losses would be significant, with no airflow through the engine whatsoever. These forces are generally lumped into the "pumping losses" description when they are actually separate losses due to reciprocation not airflow. The reason I say this can only be understood when you realize that there was an engine design, long forgotten, that pumped air through itself without reciprocation. If you have ever seen one of the rotaries stop running the prop will freewheel for a lot longer than your IC recip engine will continue to rotate when you shut if off, even though it is still pumping air.

regards
Gary

Every time I hear somebody claiming efficiency in excess of 50% I wonder what rube did the performance calculations. According to the second Law of Thermodynamics the most efficient and engine can get (Carnot cycle) is 50%. Somewhere, somebody is claiming some waste heat utilization as shaft power and that is a lie.

Sludgy is right in theory. A single is always more efficient than a multi-cylinder engine. It may shake itself and the passengers and the rest of the vehicle to bits, but by George it is more efficient than a multi of equal parameters.

The surface-to-volume ratio is why gas turbine (Brayton-cycle) engines get more and efficient as they get larger. A PT6 is not very efficient but an LM2500 is as efficient as a diesel. Big utility gas turbines are 45% efficient simple cycle and about 48% compound cycle. Size matters.

As for three cylinder two-stroke engines, I remember my old Kawasaki H2 Widowmaker. After a hundred miles your hands were numb from the vibration. Suzuki water buffaloes, with their more upright inline triples, were a bit smoother.

The wwI era rotary block / fixed crank engine design might not be suited for automotive use for several reasons: weight, physical size, torque, ground clearance, center of gravity...
Go to Rhinebeck NY to see these in operation in the air craft in which they were for a short while the best of a limited choice of powerplants. Listen to the pilots that fly these beasts tell of the shortcomings that R.I.D.E. counts as benefits, especially the problems inherent in the narrow operating range and difficulties in maintaining control with the "pulse and glide" technique needed to regulate air speed.
The drawbacks were why these rotary case/fixed piston engines were replaced by radial piston engines and were then themselves replaced by reciprocating piston engines. Each was an improvement over the best of the prior ones.

The animated engines gnome is interesting but it effectivly looks like a wankel engine - rotating combustion chambers.

Straight six is the king of all engines. It might not be the most efficient, but it beats the pants of most V-6's and V-8's. My old Jeep had a 4.0 that was running with only 2 cylinders firing for almost a year (I was young and stupid). This summer, it's getting a 4.7 stroker to make some more heat and compression. They say that if I stay out of the throttle, I can get an easy 25mpg on 35" tires. Add a few tricks here and there and who knows?

The maximum theoretical efficiency of a Carnot cycle engine is limited by the upper and lower temperature excursions within the engine itself.. I've seen stirling engines that will work on the heat produced by the palm of your hand. The efficiency upper limit is mostly based on what temperature the hot side of the engine will bear before melting or weakening to the point it breaks.

https://www.sherline.com/images/9th01a.jpg

I had a 1982 Honda 500 Ascot single street bike.. With twin balancer shafts it was by no means an uncomfortable machine to ride and the fuel efficiency was excellent. I put almost 50K on that bike without ever even changing the chain.

https://bake.smugmug.com/photos/46199462-M.jpg