|
If I had to choose. I would choose two smaller engines working together or separately over one larger engine with cylinder deactivation.
Alfa Romeo did that in the 8C grand prix engine developed before WW2. In 1950 the engine was a pair of 4 cylinder engines bolted nose to nose. All accessories were gear driven, no fan belts. One engines output flange ran a two stage supercharger while the other drove the car.
90 cubic inches and 390 horsepower @ 2 MPG.
Not a good reference for high efficiency, but the idea of two 45 cubic inch blocks working together for power with one disabled for economy is appealing.
The road racing rivalries between Mercedes and Auto Union prior to WW2 are also a fascinating study in competition between in line and horizontally opposed engines. The old Ford Flathead was basically two engines siamezed at the crankshaft with separate cooling systems, water pumps, and thermostats for each 4 cylinders. Only the radiator was a common unit.
EPA proposed a V8 that was two 4 cylinder engines that could operate in unison and separately. Maybe two 2 cylinder engines placed in an opposed piston with either side capable of being disabled to provide two cylinders for cruising and 4 for power.
While the thought process is fun, I came to the conclusion based on the capacitive storage IVT power train, that trying to make the engine more complicated is really unnecessary. I went in the other direction, more like a pressure washer engine. The 5 HP Honda in my pressure washer runs at 3600 RPM and uses something like a quart of fuel per hour. Needs no throttle control, and is fairly low stressed at 9 cubic inches and only 5 horsepower. Torque is the real objective as long as its BSFC is optimized, and I have doubts that you actually would need any more complicated design than the Toyota Corolla engines of the 70s which were beautiful little push rod staggered valve hemis.
Sophisticated multi valve engines follow the racing traditions and get more fuel and air in the engine for more power, but that may be like the old Alfa grand prix engine where sure, you are getting 4 HP per cubic inch, but at 2 miles per gallon.
I read somewhere that Toyota had actually managed to get their Corolla engine to run at open throttle and power was controlled by timing and fuel delivery without any throttle restriction. I think that is the way to go with gasoline fueled engines when you have the computational capability to inject fuel through 4 different orifices at 5 different sequences in every power stroke in an engine.
EPA also had a design for a puck in the top of th cylinder that could be elevated using oil pressure to vary the compression ratio while the engine was running.
With some of the latest improvements, Mazda has introduced an engine with compression ratio of 14 to 1. Unthinkable in the past, this is very close to the compression ratio of Indy car engines running pure alcohol. Precision control of direct fuel injection both from multiple points on the injector and at multiple points during the combustion stroke make this practical, something that was impossible on a couple of years ago.
We can only guess at what they have in their top secret research developments for IC engines, but looking at history as well as really studying the latest developments in precision control, that has only become possible with today's data processing and sensor capabilities allow only what was dreamed about very shortly ago.
Supercritical preheated fuel, injected at pressures approaching 30,000 PSI would actually spontaneously ignite without any spark ignition necessary.
regards
Mech
|