* Better thermal efficiency than current Direct Injection Diesels (i.e. less fuel per Km and less CO2 per Km to the atmosphere). OPRE's geometry shifts the combustion to the slow dead center to provide additional time to the fuel to prepare and get burned at the right time.
* Top power density: Light, yet robust, structure. One power stroke per cylinder per crank rotation. Rid of cylinder head and valve train. Keeps its torque at significantly higher (some 35%) revs than current Diesels.
* Completeness: it needs not external auxiliary equipment (like compressors etc). If necessary, it operates rid of any electrical system (mechanical injection, manual start).
* Vibration-free operation. Especially for applications with divided load, OPRE can be absolutely vibration-free, for instance as an outboard motor with two counter-rotating screws-propellers, as an electric generator set for hybrid cars etc.
* Combines higher power density than two-stroke engines with four-stroke lubrication quality (plenty of lubricant at the wrist pin side of the piston, oil rings for oil control).
* The low internal friction (two opposed pistons means half mean-piston-speed at specific revs) enables extra lean combustion at partial loads and idling. Combined with the extra lightweight structure, it allows the operation at leaner mixtures even during peak power.
* Simpler. Very simpler, and so reliable and cheap.
Compared to a two cylinder BMW 850cc boxer motorcycle engine, the 500cc OPRE Single-cylinder Direct-Injection-Diesel has
similar peak power, flatter torque curve, the same number of combustions per crank rotation and less inertia vibrations
(i.e. has better quality / smoothness), is way shorter (500mm wide versus 700mm), has more compact combustion chamber
(bore 80mm, stroke 50+50=100mm), has way lower consumption and emissions (a direct injection Diesel with extended time for
combustion versus a spark ignition) and has half its weight.
Compared to a conventional four-stroke four-cylinder 1200cc Direct Injection Diesel (peak power at 4000 rpm), the 500cc
OPRE Single-Cylinder Direct-Injection-Diesel has similar power (at 6000 rpm), has one power stroke per crank rotation
versus two of the four cylinder, has way less inertia vibrations, has lower consumption and emissions, has way lower
weight and size.
Compared to an opposed piston Junkers engine (successful Airplane Diesel engine with top thermal efficiency at its time,
top reliability and top power density, successful also military engine in tanks, submarines etc) the OPRE engine seems
similar, at first look, but in fact it is quite different.
For non-military use the Junkers engine has two major problems yet to solve:
First is the scavenging problem. Junkers needs external scavenger / blower and a lot of power to drive it. The
external scavenger defines the characteristics of the engine. For instance, the centrifugal blower used in airplanes
gives a peaky torque curve to the engine that has to operate from, let say, 3000 to 3300 rpm.
The OPRE engine solves the scavenging problem by the built-in zero-cost volumetric piston-type scavenging pumps
at the ends of the cylinder. They enable a wide-rev-range and a flat-torque-curve. The power necessary for the scavenging
pumps is provided directly from the combustion side of the piston, without any transmission system in-between.
Second is the lubrication problem of Junkers, and of all other two cycle engines with ports, like OPOC, Orbital etc.
In the conventional two-stroke with ports, the piston thrusts heavily onto the cylinder wall at the hot (especially at
exhaust side) ports area. A lubricant film is necessary on the interface between piston skirt and liner, around the ports
area, and a quantity of lubricant is destined to escape or to get burned.
In the OPRE engine, because the pistons are upside-down, the thrust loads are away from the ports area, at the wrist
pin side of the piston, where the cool cylinder liner has no ports/slots and the oil has neither way to escape nor way to
get burned, while at the other side of the piston, the piston never touches the liner and the ports.
The 4400 rpm of the peak power of the best Junkers Diesel engines can rise, in the case of OPRE, at 6000+ rpm (with
proportional increase of the power density) because the "geometry" of OPRE provides some 35% additional time for the combustion.
Compared to the Sulzer RTA marine engines, with the top fuel economy in the world, the OPRE engine is a cross head engine,
as well, i.e. the combustion piston does not touches the liner.
Compared to the Wankel rotary engine: in the case of divided load (as a portable-flyer, for instance, with two counter-rotating
rotors, or as an electric power set with two counter-rotating electric generators) the smoothness and the overall vibration-free
running of OPRE is better because OPRE's basis is not only rid of inertia vibrations (as the Wankel) but it is also rid of
combustion pulses vibrations.
For the rest, the Wankel rotary engine has significant problems yet to solve, like
the sealing of the combustion chamber, the lubrication, and above all the poor thermal efficiency: for each KWh of energy generated it emits much more CO2 to the atmosphere than the conventional engine.
Range Extender Modules (REM) based on the Wankel rotary engine, like those of AVL and of FEV, are presented as having the best NVH (Noise Vibration Harshness) properties.
Compare their NVH properties to those of pattakon OPRE REM (exe animation, 700Kb).
OPRE engine applications
As the main power unit for cars, trucks, bikes, boats, airplanes, helicopters, electric generator sets,
portable-flyers (power density + vibration free + fuel economy + reliability) etc, single or multicylinder,
compression-ignition or spark-ignition.
Also in special applications like water pumping, hybrid car battery charger, hydrid vehicles high
pressure oil pump, robot's power unit etc.
In case of spark ignition cycle, the free breathing (extended port area, through scavenging, volumetric built-in pumps),
the reduced friction because of the half mean-piston-speed (two piston-strokes make the combustion-stroke) and
the long piston dwell at combustion dead center (more efficient combustion) allow the spark ignition OPRE to rev at way
higher revs than current racing engines. It is also the "one combustion per crank rotation per cylinder". For normal and
2. Electro-Hydraulic VVA (PattAir and PatAir)
The state-of-the-art is the MultiAir of Fiat (called also UniAir of Schaeffler-INA).
It works according the "Ingoing Air Control": the load is controllably reduced by preventing more "Ingoing Air" from entering the cylinder. The sooner the intake valve closes during the suction stroke, the less air is left to enter the cylinder and the lighter the load.
The PatAir, based on very similar hardware (only the duration of the camshaft needs to change), works according:
either the "Ingoing Air Control" of Fiat,
or according the "Outgoing Air Control" of pattakon wherein the load is controllably increased by preventing more "Outgoing Air" from leaving the cylinder. The sooner the intake valve closes after BDC, during the compression stroke, the heavier the load.
The thermodynamic cycles of the "Ingoing Air Control" (Fiat) and of the "Outgoing Air Control" (pattakon) are different.
The "Outgoing Air Control" cycle avoids not only the underpressure, under part load, into the intake manifold (as the throttle-less VVAs, like the Fiat MultiAir and the BMW valvetronic, do) but it also avoids the underpressure into the cylinder by avoiding the expansion of the charge before the compression.
By minimizing the pumping-loss, by avoiding the consumption of mechanical-energy to just expand and warm the charge, by keeping alive the turbulence and swirl during combustion and by improving the mixture homogeny the "Outgoing Air Control" minimizes the mechanical-energy loss and optimizes the combustion.
The PatAir is an evolution of the MultiAir because it can operate not only according the infinite available modes of Fiat MutliAir cycle, but also according the infinite modes of pattakon "Outgoing Air Control" cycle.
The PattAir operates according the "Outgoing Air Control" cycle.
The PattAir opens the valves true mechanically (the hydraulic system gets into play only during the valve closing) and avoids the smoothing / deformation of the actual valve lift profile introduced by the hydraulic circuit of MultiAir and Patair.
The PattAir fits to sport engines and to higher revving.
The PattAir fits to the control of exhaust valves, too. The opening of the valve is mechanical, so the hydraulic system is not overstessed.
The application of the PattAir on used engines, as an "Upgrade Kit", is simple.
The PattAir is based on existing / tested parts and technology.
The extremely accurate, instant, flexible, cheap and easy electronic control is the key advantage of the MultiAir, as well as of the PatAir and of the PattAir.
The VVA system is not based, any longer, on an extreme construction accuracy of the hardware.
The ECU, based on the feedback, controls independently the operation of each cylinder by just aligning the opening and closing times of the solenoid valves.
It is simple to modify and control complicate engines like the V-8 and the V-12.
The side cam American V-8 engines can easily turn to efficient and clean engines.
The electronic control offers flexibility: for instance, a PatAir four inline engine is easy to operate with one cylinder deactivated, with another cylinder running at full load, with another cylinder running at medium load according the "Ingoing Air Control" cycle and with another cylinder running at medium load according the "Outgoing Air Control" cycle. It is also easy to swap, a few dozens of times per second, the above modes among the cylinders.
Combining the PattAir with one of pattakon VCRs, a Variable Capacity Engine (VCE) results that can operate at all revs-loads at optimum efficiency, leaving no room for the hybrids and limiting the use of the Diesel engines.
3. Variable Compression Ratio (pattakon VCRs)
The constant compression-ratio of the conventional engine is as much a compromise as the constant valve-lift.
The engine would have better thermal efficiency, better torque, more power, less emissions etc if the compression-ratio
were optimized for the instant conditions of operation (load, revs, quality of fuel, air temperature, cooling temperature,
altitude, EGR etc).
At partial load (for instance urban cycle, medium speed motion etc) the 12:1 compression-ratio is too low. A
16:1 compression-ratio would be much better for economy, emissions, torque, response etc.
At heavy load (for instance acceleration, high speed motion, uphill etc) a 10:1 compression-ratio offers more power and
torque than the 12:1 because the latter, in order to avoid knocking, has to shift the spark a lot.
Things get worse for conventional in case of supercharging.
There have been proposed many VCR mechanisms so far. A few of them have been officially measured and reported to offer
what theory predicts: improved economy, less emissions, more power, more torque etc.
The problem is that together with the VCR come VCR's side-effects, like complication, extra-weight, extra friction,
difficult control, vibrations, reliability issues, high revving incapability etc.
To cut in pieces the crankshaft, or to support the crankshaft on moving bearings, or to introduce extra transmission
between crankshaft and gearbox, or to generate heavy bending loads and then to reinforce the structure of the engine to
receive them, or to introduce additional parts in the main kinematic mechanism or ... sounds not as promising as the
initial VCR idea.
Two-step (switchable) VCRs have been proposed as a compromise. They are like the "two step" valve train systems: they
do improve things (they are a step ahead conventional) but they cannot compare to continuously - or infinite step - variable
systems (which look many steps ahead conventional). A look at the Fully variable VVA or FVVA is explanatory.
A two-step VCR improves the operation of an engine, but it is only a demi-solution. Its "switchable" character creates
problems: the power and torque curves cannot be smooth, the control is difficult (especially during the "inevitably
noticeable" transition from the one compression-ratio to the other), it cannot control the HCCI combustion etc. The worse is
that most of the time the engine still operates away from the optimum compression ratio.
Quoted from Variable Valve Actuation Roller version : "Two-step compared to continuously variable
systems: it is like having a shoe-shop offering just two sizes of shoes, one for children and one for adults. If the customer
is lucky OK, if not..."
Comparing pattakon VCRs to the state-of-the-art VCRs Multi-link VCR (Nissan's, Daimler's, Honda's etc) versus patcrank VCR
The multi-link VCR is based on a linkage between the crankpin, the big end of the connecting rod and the crankcase.
This linkage comprises a rocker pivoting about the crankpin, a rod and a control shaft.
The big end of the connecting rod is pivotally mounted at one end of the rocker, the rod is pivotally mounted at the other end of the rocker. The other end of the rod is pivotally mounted on the control shaft.
The displacement of the control shaft, relative to the crankcase, changes the compression ratio.
Because the rocker undergoes heavy bending loads, it is heavy and therefore its motion adds inertia loads and friction.
The piston force (due to gas pressure and inertia) loads the crankpin with some 1.5 times heavier force, because of the fulcrum action of the rocker. The rod is also loaded by about half of the piston force. All bearings undergo the respective forces adding friction.
The long chain of parts and bearings is under heavy inertia and combustion forces limiting the high revving capability and adding friction. Such a long chain of parts, being under such loads, adds torsional, twisting and flexing possibilities that call for double bearings, adding further mass, friction and reliability issues.
The inertia vibrations and the smoothness of the engine vary with the compression ratio. The displacement of the piston versus the crankshaft angle depends also on the compression ratio selected.
Because the control shaft handles a big part (about half) of the piston force, it needs to be adequately massive with strong supporting on the crankcase, away from the crankshaft axis, which calls for a heavier crankcase.
The inertia forces and torques resulting from the motion of the additional parts, reduce - in some arrangements - the external vibrations of the engine, yet these strong forces and torques load the crankshaft and the crankcase, limiting the high revving capability and increasing the friction. Similar case is the prerack_VCR_(animation_3.5MB) wherein a single cylinder VCR engine is, without balance shafts, perfectly balanced as regards its inertia forces, yet the inertia stresses limit its high revving capability.
The application in Vee engines (like the conventional V-8) is more trouble: per piston it needs a rocker and a rod, while a separate control shaft is necessary per bank of cylinders (for a V-8 it needs eight rockers, eight rods, two control shafts, i.e. 18 heavy, expensive and difficult to make and support parts).
patcrank VCR resembles to the multi-link VCR in that it is also based on a linkage between the crankpin, the big end of the connecting rod and the crankcase.
Instead of the rods (one per piston) of the state-of-the-art multi-link VCR, patcrank VCR needs only one (for the entire engine) displaceable thin and lightweight secondary crankshaft.
The small eccentricity of the big end of the connecting rod from the crankpin, and the rotation (and not angular oscillation) of the secondary crankshaft make the difference.
The support of the connecting rod around the crankpin eliminates any chance for twisting.
The forces from the piston and the connecting rod pass "directly", through the eccentric pin, to the crankpin, creating insignificant bending and twisting loads on the "rocker" (i.e. on the secondary connecting rod of the patcrank VCR) and allowing slim and true lightweight "rocker" that generates way lower inertia loads and friction.
The force on the crankpin is only 0.95 times the piston force (due to gas pressure and inertia). The force on the secondary crankshaft is only 0.05 times the piston force. The control frame of patcrank VCR carries only the 1/20 of the piston force, enabling way faster response compared to the state-of-the-art multilink VCR where the control shaft carries the 1/2 of the piston force.
The displacement of the piston versus the crankshaft angle is identical to that of the conventional engine and remains the same for all compression ratios.
The inertia balance and smoothness of the engine is independent of the selected compression ratio.
The application in Vee engines with common crankpin is easy and even more economic compared to the application in inline engines. All it takes is one secondary connecting rod per pair of pistons and one (for the entire engine) displaceable secondary crankshaft. For instance, for a V-8 it takes four slim and lightweight secondary connecting rods and one thin and lightweight crankshaft, i.e. 5 lightweight, and cheap to make, moving pieces in total, plus one slow moving control frame.
A modified V-8 patcrank VCR has as vibration-free-operation as the original conventional V-8, no matter what the selected compression ratio is.
The range of available compression ratios of the patcrank VCR is as wide as desirable, for instance from below 7:1 to above 20:1.
FEV VCR and the similar versus patcrank VCR
To change the compression ratio, FEV's VCR displaces the rotation axis of the crankshaft relative to the crankcase. The frame that holds the crankshaft needs to be very strong. The crankcase that holds the frame needs to be even stronger. The additional transmission between crankshaft and gearbox adds friction, noise and reliability issues. A system to keep synchronized the camshafts with the moving crankshaft is also necessary.
SAE awarded FEV's VCR for being a smart breakthrough.
patcrank VCR resembles to FEV's VCR in that it displaces the rotation axis of a crankshaft relative to the crankcase, too. However, instead of displacing the main crankshaft (that stays at its conventional position firmly connected to the flywheel and through the clutch to the gearbox), patcrank VCR displaces a thin and lightweight secondary crankshaft that carries a tiny part of the piston forces, making the response way faster. The control frame that holds the secondary crankshaft is proportionally thinner and lightweight. The sprockets and the timing belt (or chain) that synchronize the camshafts to the crankshaft remain the conventional.
Gomecsys VCR versus patcrank VCR
To change the compression ratio, Gomecsys VCR changes the phase of an eccentric ring interposed between the big end bearing of the connecting rod and the crankpin.
A gearwheel around the crankpin holds the eccentric ring. By some other gearwheels the phase of the eccentric ring, relative to the crankpin, is controlled, and so the compression ratio.
The robustness of the crankshaft degrades (multi-piece "assembled" crankshaft with cuts and passages for the gear wheels) as well as the supporting of the crankshaft on the crankcase (by omitting some main crankshaft bearings).
Adds balance shafts of 1st and 2nd order.
The 720 degrees cycle adds "new" inertia vibrations of half order.
The gearwheels on the crankpins generate and undergo heavy centrifugal forces that increase friction and flex the gearwheels.
Is incompatible with many typical cylinder arrangements.
Difficult to cope with high revving.
On the other hand, Gomecsys VCR provides over-expansion and 720 degrees cycle. It is also fast responding due to the small loads on the control mechanism.
patcrank VCR resembles to Gomecsys VCR in that it is also based on an eccentric ring interposed between the big end bearing of the connecting rod and the crankpin.
But patcrank VCR keeps the original single piece robust crankshaft and the main bearings as they were, is applicable in any engine arrangement, does not add vibrations and stresses, is rid of gearwheels, is rid of heavy (i.e. creating strong inertia loads and friction) quick moving parts.
All it takes is one secondary thin and lightweight crankshaft, one slim and lightweight secondary connecting rod per crankpin and a lightweight control frame that moves only when a different compression ratio is desirable.
Two-step-VCR versus patcrank VCR
Ford's "variable length connecting rod" VCR, Honda's two-step-VCR, FEV's two-step-VCR and the similar, offer only two compression ratios, i.e. most of the time the engine operates far from the ideal compression ratio.
The complication they introduce (multi-piece - i.e. heavy - piston or connecting rod, locking pins and springs, high pressure oil pump, holes on the connecting rods to pass the control oil etc) is disproportional to what they offer.
In comparison the patcrank VCR offers, with less complication, the two compression ratios of the two-step-VCR and infinite more compression ratios in a wide range.
MCE-5 VCR versus patrack VCR
MCE-5 VCR is based on rack-gears and on synchronized rollers for the thrust loads. To control the compression ratio, a control rack is displaced.
The block of the engine needs, per working cylinder, one additional control cylinder of similar size.
The quick moving parts are heavy and big in dimensions.
The inertia loads are heavy.
The rev limit is low.
The asymmetrical form of the piston adds inertia thrust loads on the cylinder wall.
The rollers need heavy preloading.
Because of the typical 20 degrees inclination of the teeth surface of the piston rack-gear, the one-sided piston rack-gear of the MCE-5 VCR adds an additional force (36% of the piston force due to gas pressure and inertia) that overloads the synchronized roller at any angle of the connecting rod.
The patrack VCR resembles to MCE-5's VCR in that it is also based on rack-gears and on synchronized rollers for the thrust loads.
But the two-sided piston rack-gear of the patrack VCR loads the synchronized rollers with three times weaker forces because it eliminates the thrust loads generated by the inclination of the piston rack-gear teeth surface.
The quick moving parts are smaller and lightweight, allowing high revving.
The thrust loads of the piston on the cylinder are insignificant.
The rollers need not heavy preloading.
The size of the block is conventional.
SAAB SVC versus pat-head VCR
To change the compression ratio, SAAB's SVC displaces (rocks) the cylinder head together with the cylinder block relative to the crankcase.
Its architecture (the cylinder head together with the cylinder block are pivotally mounted on the crankcase) generates heavy bending loads on the cylinder block and on the crankcase.
The kinematics and the inertia vibrations of the engine depend on the selected compression ratio.
It makes difficult the sealing (oil and noise) of the crankcase.
It makes difficult the connection of the exhaust system with the cylinder head.
It degrades the quality of operation of the engine by additional noise and vibrations.
The pat-head VCR resembles to SAAB's SVC in that it also displaces the cylinder head together with the cylinder block relative to the crankcase.
But the pat-head VCR displaces the cylinder head and the cylinder block linearly (i.e. parallel to themselves) and keeps untouched the kinematics and the balance of the engine, supports the forces in the proper way without creating heavy bending loads neither on the cylinder block nor on the crankcase, seals efficiently (oil and noise) the crankcase, allows conventional exhaust system conventionally secured on the cylinder head and maintains the operational quality (smoothness) of the engine.
In brief, the pat-head VCR is a continuously / infinitely Variable Compression Ratio mechanism that offers a compression-ratio range from less than 7:1 to more than 20:1.
It is mechanical.
It leaves untouched the kinematic mechanism of the engine and the smoothness of the engine and the high revving
capability of the engine.
The crankshaft, the connecting rods, the piston pins and the pistons are conventional and they
move exactly as in the conventional engine.
The mechanism receives the combustion loads and the inertia loads smartly, creating neither significant bending loads
nor side effects.
It exploits the empty space into the conventional cylinder head.
The synchronization between crankshaft and camshafts is simple and accurate: A free roller (the red one, near the camshaft sprockets, shown in the VCR.wmv, 3.0MB, video-animation) has its center secured on the crankcase, i.e. its center remains immovable when the cylinder head moves up or down to change the compression ratio. This free roller changes the direction of the belt / chain, coming from the crankshaft sprocket, for about 90 degrees before it meshes with the first camshaft sprocket. Another free roller, beside the crankshaft sprocket, is the tensioner that takes the lash of the belt / chain (the conventional lash and the lash resulting from the approach of the camshafts to the crankshaft). This simple geometry keeps the timing between crankshaft and camshaft unchanged, no matter what the compression ratio is, i.e. the valves open and close at the same crankshaft degrees either at 20:1, or at 7:1 or at any other available compression ratio.
It can easily be adapted in multicylinder engines (like 2 or 3 or 4 or 5 or 6 cylinder in line, like 6 or 8 cylinder
in Vee etc).
It fits even to small single cylinder engines, like those in motorcycles, electric generators etc.
The compression-ignition (Diesel) engines can also take advantage of the mechanism. 20:1 is a good compression-ratio
for the "cranking" (even without glow plugs) and the warming of the engine, while 14:1 (or even lower) is a good compression-ratio
for running the warmed engine.
In mass production the additional manufacturing cost is insignificant.
It is a simple, lightweight and compact, yet robust and fully functional VCR.
Compared to the state of the art, pattakon pat-head VCR is a complete solution that comes without significant side effects.
4. Desmodromic Variable Valve Actuation (DVVA)
Key advantages The DVVA is a desmodromic and fully-variable, Variable Valve Actuation (VVA) system.
The valves open and close positively.
The kinematic mechanism holds the valve the whole time, during opening and during closing.
There are neither valve springs to restore the valves (so the valves become significantly shorter and lighter), nor
springs to restore the rest parts of the DVVA mechanism.
The valve lift changes continuously from net zero to a maximum (14+ mm).
The valve duration changes also continuously from net zero to a maximum (360+ degrees).
The valve lift and the valve duration change independently, i.e. for each valve lift there are infinite
available valve durations to choose from, and for each valve duration there are infinite available valve lifts to
choose from and approach better the ideal valve lift profile for the existing operational conditions (revs, load,
air temperature, cooling temperature etc).
The motion of the valves is smooth (small acceleration and jerk).
All the quick moving parts of the mechanism are light and robust, allowing reliable operation at extreme revs (motoGP).
The control shafts move slowly and only when a different valve lift profile is desirable.
With either mechanical or hydraulic valve lash adjusters.
It is a pure mechanical, fully variable, compact valve train.
Comparing the DVVA
BMW's valvetronic is a lost-motion VVA. It is variable, but not fully variable. For each valve lift, valvetronic has
only one available valve duration (this valve duration is not an optimized one for the specific lift, it is
just what the mechanism can give) while DVVA has infinite, and for each valve duration valvetronic has one only
available valve lift (again not an optimized valve lift for the specific valve duration, just what the mechanism can give)
while DVVA has infinite. The valvetronic is based on a relatively "heavy" oscillating member that
"opens" under the camming action of the camshaft and "closes" under the restoring action of a vertical-long-big-spring.
The valves in valvetronic need their own conventional valve springs to close. The big springs and the heavy parts
restrict valvetronic to not high revving applications (rev limiter at 6800 rpm) and this is why valvetronic is missing
from BMW's sport cars.
Nissan's VVEL is also a lost-motion VVA, like valvetronic. It is as variable as valvetronic, but not fully variable.
It needs valve springs to restore the valves. The VVEL mechanism is demi-desmodromic: there are valve springs to restore
the valves but there are no other springs, like the "vertical-long-big-springs" of the valvetronic mechanism. This is why
Nissan's top sport coupe 370Z (VQ37VHR-V6-VVEL) can operate at 7400rpm to provide 94.7bhp/lit specific power. The "maximum
rpm" of the same sport engine is set to 7500 rpm (only 100rpm higher than the peak power revs!) saying a lot about the
limitations of the current VVAs.
Toyota's "valvematic" has similar limitations to BMW's valvetronic.
provides infinite times more valve lift profiles to better optimize
the breathing of the engine, and
allows as high revs as the underneath mechanism can stand (block, crankshaft, con-rods, pistons). The ideal VVA is the one
that optimizes the breathing of the engine at all revs and every load.
The DVVA, depending on the angular position of its control shafts, can "play" either as Lost Motion VVA (valvetronic for
instance), or as Constant Duration VVA (pattakon VVA rod version, for instance), or as a single mode Ducati Desmo valve
train, or as anything in-between them.
The one moment DVVA can operate accurately at 300 rpm, 0.15mm valve lift and 50 degrees valve duration, while the next
moment DVVA can rev at 15,000 rpm, 14mm valve lift and 360 deg valve duration.
Most VVAs control exclusively the intake valves, either because of cost, or because they cannot control the
exhaust valves. The following is a copy from engine-technology-INTERNATIONAL:
. . . Valeo refers to the design (i.e. their electromagnetic VVA) as
"half camless". The reason for this is that the forces required to operate the exhaust side are so high, the performance
benefits are off set by the increased parasitic losses . . . The spokesman adds: The main benefits are on the inlet side
as pumping losses can be reduced. We concluded that if 80% of the benefit is on the inlet side, then this is
the best balance. . . . the two concepts together (the electromagnetic "half camless" and a mild hybrid based on StARS+X
technology) have been given a dramatic boost by the award of US$108 million (a hundred and eight million US dollars)
from the French Industrial Innovation Agency
In case of turbo-supercharging the 80%-20% balance (between the benefits from inlet valve control and exhaust valve
control) claimed by Valeo, goes to 50%-50%, maybe more, for both spark and Diesel engines. And the opening of an
exhaust valve of a turbo engine takes more force (and energy).
The DVVA can control the exhaust valves, as well.
It is significant for the breathing and the combustion to optimize not only the intake valve-lift-profile but also the
exhaust valve-lift-profile, it is also significant for the high revving capability of the valve train to remove all valve
springs and leave the desmodromic mechanism to open and to restore all valves.
DVVA and Downsizing
Automotive journalists voted "VW-1400cc-TSi-Twincharger" as the best green engine of the year 2009 for combining high power
and power density (178 bhp, 127 bhp/lit) with low(?) emissions / consumption (144gr/Km CO2). A downsizing that works,
In fact, VW-1.4-TSi-Twincharger is a complicated engine with many auxiliary subsystems (turbocharger, compressor, pulleys,
coolers etc). Its size and weight (subsystems included) are close to those of a naturally aspirated 2000cc, its cost is higher.
Its power and emissions are, according the official tables, not better than the 170 bhp and the 146 gr/Km CO2 of a BMW-320i-sedan,
2000cc naturally aspirated having 1445 Kp empty-weight.
Successful downsizing would be a 1400cc engine providing the power and torque of a 2000cc with the emissions and
consumption of a 1000cc at the cost of a 1600cc.
Downsizing can better than TSi-Twincharger:
Consider the case of a four in line motorcycle engine, with the DVVA on its cylinder head, mounted in a small car like
Aygo. A typical 1000cc motorcycle engine makes today 180 bhp (180 bhp/lit) naturally aspirated. With a DVVA on the cylinder
head, the 1000cc motorcycle engine has many reasons to provide more power than 180 bhp and no reason to provide less. Selecting
the mode (i.e. the angular position of the control shafts) of the DVVA, the same engine turns into a soft, smooth,
clean, torquie and driver-friendly 1000cc engine for family cars, more green than the current green 1000cc auto-engines (like
Toyota Aygo 998cc, 67 bhp, 67bhp/lit, 109 gr/Km CO2, voted as the best Sub1-litre engine for 2009). The 1000cc-DVVA can easily
give 95gr/Km CO2 (that is 2/3 of VW-TSI-Twincharger or 87% of Aygo's 1000cc), because the DVVA optimizes continuously the
breathing and the combustion, while the conventional 1000cc auto-engine is only a compromise between economy-power-torque etc.
The typical driver of the VW-1.4-TSI-Twincharger and the typical driver of the 1000cc-DVVA will both use the peak power of
their engines "once in a life-time", yet most magazine and web articles will focus on the peak power of the engines. For some
95% of their life-time both engines are destined to provide only a small fraction (like 1/10 or even less) of their peak power.
For instance cars like Toyota Aygo and VW Golf need no more than 20 bhp to maintain 100 Km/h velocity on a level road.
The best "green" engine has to combine at partial loads and at low-medium revs (i.e. where the engine works most of the time)
as high thermal efficiency and as low emissions as possible with true driver friendly operation. If the same engine, without
sacrificing the partial load / low-medium revs operation, can also make top peak power, it is significant. Otherwise the top
peak power is just a marketing trick, a trap.
A simple-minded example: the driver of a normal 1000cc Aygo drives for 10 Km in a town, while the driver of a VW-Golf,
powered by the "best green engine of the year 2009" VW-1400cc-TSi-Twincharger, follows the Aygo.
The Aygo emits in total some 1 Kgr of CO2 into the atmosphere while the Golf emits in total some 1.5 Kgr CO2 to cover the
The analogy is not 109 to 144 (109gr CO2/Km is the combined-cycle, i.e. urban-cycle and extra-urban cycle, emissions for
Aygo while 144grCO2/Km is the combined-cycle emissions for Golf-TSi-Twincharger) but worse for Golf, because Golf engine is
oriented to extra-urban driving.
As Golf's official urban cycle consumption is 8.1 litter/100Km (Golf-TSi-Twincharger-160bhp) and Aygo's official urban
cycle consumption is only 5.5 litter/100Km, Golf emits 47% more CO2 (urban-cycle) than Aygo for the same distance.
Golf is heavier than Aygo, yet a fully loaded Aygo remains way more efficient, clean and green in urban-cycle than an
It is a matter of compromise:.
For the sake of the "peak power", the "best green engine of the year 2009" compromises with significantly reduced partial
load / low revs thermal efficiency and emits some 50% more CO2 than a cheap (if not the cheapest) conventional-technology engine/car.
On the other hand, for the sake of the fuel economy and the low emissions, Aygo's engine compromises with low power
density (67 bhp/lit, almost half than the 127 bhp/lit of VW-1400cc-TSi-Twincharger). With a DVVA on its cylinder head, the
3-cylinder 1000cc engine of Aygo can make 110 bhp peak power at 8000rpm (where the mean piston speed is 22.4m/sec) naturally
aspirated, with more torque, better fuel economy and lower emissions than the original Aygo engine.
More extreme (and still "greener" than the original Aygo) is an Aygo powered by a short-stroke 1000cc DVVA motorcycle-engine
(the short stroke allows high revving for extreme power density). It can do all without compromises: top power density, top fuel
economy, flat torque curve, low emissions, smooth idling, driver friendly operation etc.
What the DVVA offers is "multiple-character": the same engine operates the one moment as a friendly, torquie, clean,
economic, smooth engine and the next moment, the same engine operates as a pure racer with all intermediate characters available.
A further step: The above-described 1000cc-DVVA engine combined with the pattakon VCR.
Family car engines, sport car engines, racing engines, motoGP engines, F1 engines, Diesel engines, motorcycle engines etc.
5. Idle Valve
In order to keep low, smooth and clean idling without a throttle valve (pumping loss), a VVA needs
extreme operational (not just manufacturing) accuracy for the valve lifts.
The intake valves of the
VVA roller version (a throttle-less VVA) keep idling at low revs with only 0.15mm intake
valve lift. Then the same intake valves operate at 9000 rpm to give the peak power. Then, when the gas pedal is released,
the same intake valves operate again at low revs and 0.15mm valve lift to make the engine idle.
If a 0.02mm tolerance is attainable for the intake valve lift, the ratio (0.15+0.02)/(0.15-0.02) = 1.3 indicates that a
cylinder can suction 30% more charge than its neighbor cylinder!
An idea of what the 0.02mm is: by changing the temperature of the 102mm long intake valve for 17 degrees centigrade, its
length changes by 0.02 mm. On this basis, to ask for less tolerance (say 0.005mm) is meaningless.
Either with mechanical VVA, or with pneumatic VVA, or with electromagnetic VVA, or with hydraulic VVA, or ... there is
no cure. It is not reasonable to expect from a big valve (and its kinematic mechanism) to run the one moment at high revs /
high valve lift / high stress and the next moment to run at very low revs / very low valve lift / with extreme accuracy
over its motion.
The solution is to keep completely closed the big intake valves during idling, and to leave to other small metering
valves (the Idle Valves) the idling. That simple.
The idle valves can be very simple, for instance one way valves activated by the vacuum into the cylinder.
For more sophisticated applications, electromagnetically activated lightweight, short stroke, popet valves is another
choice. To open and close, exclusively at low revs, a short-stroke lightweight valve is an easy job for an electromagnet,
while the control is complete and accurate.
The pattakon Idle Valve is a general solution, applicable to all existing and future VVAs.
Valve lift from 0 to 12+ mm.
High revving capability: over 9.000 rpm at full lift.
Simple, compact, reliable, durable, low friction, accurate (small number of interfering joints).
Smooth valve motion at all modes (low acceleration and jerk).
All the quick moving parts are lightweight and robust (for the loads they carry).
Conventional valve lash control (either mechanical or hydraulic).
Robust control-shaft that moves only when a different valve lift profile is desirable.
Control on the actual overlap without a VVT.
Throttle-less, if desirable.
Simple control: the foot of the driver presses the gas pedal that rotates, by the gas cable, the control shaft that changes the valve lift. ECU main parameters for injection and ignition tables: control-shaft angular displacement (by a TPS sensor) and revs. No need for servomotors.
Applicable on intake and exhaust valves.
Applicable on old and new cylinder-head designs.
For spark ignition and compression ignition engines.
For all engine arrangements, from the cheap single cylinder to the sophisticated luxury multicylinder.
7. Rotary Engine / Pump
The Wankel rotary engine features the freest breathing, being rid of camshafts, valves, springs etc. This toroidal rotary engine features as free breathing as the Wankel rotary engine, being also rid of camshafts, valves, springs etc.
The attenuated combustion chamber and the poor sealing have been, and still are, Wankel's Achilles' heel, causing way lower thermal efficiency than conventional. This toroidal rotary engine has not the sealing problems of the Wankel rotary: its "piston rings" - more than one if desirable - keep "surface contact" with the toroidal "cylinder", while Wankel's rotor apex seals - inevitably one only per rotor apex - keep poor "line contact" with the epitrochoid. It is also the shape of the combustion chamber of this toroidal engine which is as compact as the combustion chamber of the conventional reciprocating engine. The good sealing, the compact combustion chamber and the low friction enable comparable to the conventional, if not better, thermal efficiency.
The two-rotor Wankel rotary engine completes two combustions per power shaft rev, while this toroidal engine completes four combustions per power shaft rev (one per chamber).
The Wankel rotary engine needs a pair of gear wheels to synchronize the motion of the rotor with the power shaft, it also needs counterbalancing weights on the power shaft. This toroidal rotary engine needs neither gear wheels nor counterbalancing webs.
For equal "expansion cycle" (or power stroke) duration (i.e. time in seconds), the power shaft of the Wankel rotates three times faster, while the crankshaft of the conventional rotates two times faster than the power shaft of this toroidal rotary engine.
This built-in revs reduction is beneficial in many applications. For instance when a propeller of an airplane is driven directly by the power shaft.
When an electric generator is driven at 3000 rpm directly by the power shaft of the Wankel, the time for the "expansion cycle" of a chamber of the Wankel engine is 0.015 seconds (too long, especially when combined with the poor sealing of the Wankel and the worst surface to volume ratio of the chamber during combustion). When the same electric generator is driven at 3000 rpm by the power shaft of this toroidal rotary engine, the time for the "expansion cycle" of a chamber is only 0.005 seconds, i.e. 3 times shorter than in the case of Wankel.
The Wankel rotary is:
aerodynamically (breathing) far better than conventional,
dynamically (mechanism, smoothness, simplicity) far better than conventional,
thermodynamically (sealing, heat loss, combustion propagation, combustion completeness) far worse than conventional.