Abstract: Two turbochargers are arranged vertically near a one side of a crank-shaft direction at a one-side face of an engine body so that the large-size turbocharger is located above the small-sized turbocharger, and an exhaust-gas purification device is arranged an open space made on the other side of the crank-shaft direction so that its exhaust inlet is located above and its outlet is located below. Accordingly, the turbochargers and the exhaust-gas purification device can be arranged compactly and the layout of some devices around the engine can be facilitated.

Abstract: Methods are provided for controlling a turbocharged engine having a throttle and a turbocharger. One example method comprises, moving the throttle during boosted conditions, separating out effects on the throttle inlet pressure into a first portion corresponding to disturbances caused by the movement of the throttle, and a second, remaining, portion. The method further comprises adjusting the turbocharger based on the second portion and not the first portion.

Abstract: A cooling circuit and an independent heat recovery circuit are associated with an internal combustion engine. A coolant is circulated a pump in a first and a second cooling sub-circuit. An increase in pressure in a work medium is achieved within the heat recovery circuit by a pump. This work medium is changed from liquid aggregate state to vaporous aggregate state and back to the liquid aggregate state in heat exchangers. This work medium is divided after the pump into two parallel partial flows and is changed into vaporous state in a first parallel branch in an EGR heat exchanger through which recycle exhaust gas flows and in a second parallel branch in an exhaust gas heat exchanger through flow exhaust gas downstream of the low-pressure turbine flows. This vaporous work medium is then fed to an expander and is then conducted through a cooled condenser and, liquefied again.

Abstract: A method for reducing imbalance between multiple compressors supplying air to an engine is disclosed. In one embodiment, engine boost pressure is limited by choking flow through a compressor. The method may reduce compressor surge during some operating conditions.

Abstract: An internal combustion engine is provided with an exhaust gas pipe for taking exhaust gases from the engine's combustion chamber and an intake pipe for supplying air to the combustion chamber. The engine includes a turbo charging system with a high-pressure turbine that interacts with a high-pressure compressor and a low-pressure turbine that interacts with a low-pressure compressor, for recovery of energy from the engine's exhaust gas flow and pressurizing of the engine's intake air. The high-pressure turbine is connected to the low-pressure turbine via a duct. An exhaust gas pressure regulator is located in the duct between the high-pressure turbine and the low-pressure turbine.

Abstract: A turbocharger system comprises a first relatively small high-pressure (HP) turbocharger (1) and a second relatively large low pressure (LP) turbocharger (2). The turbine (6) of the LP turbocharger (2) is connected in series downstream of the turbine (4) of the HP turbocharger (1) in a first exhaust gas passage (11). An exhaust bypass flow passage (12) provides a bypass flow path around the HP turbine (4). A rotary valve (8) is located at a junction of the bypass flow passage (12) and a first exhaust gas flow passage (11). The rotary valve (8) comprises a valve rotor (19) which is rotatable to selectively permit or block flow to the LP turbine (6) from either the first exhaust gas passage (11) or the bypass gas passage (12).

Abstract: A system for driving an EGR stream for an engine includes an exhaust gas turbine, a main compressor and a supplemental EGR compressor. The turbine drives the main compressor to pressurize intake air and drives the supplemental EGR compressor to pressurize an EGR exhaust gas stream to be introduced into the intake air system. A supplemental EGR compressor takes suction of exhaust gas downstream from the turbine. A three-way valve proportions exhaust gas between the engine exhaust gas discharge conduit and the suction of the supplemental EGR compressor. The turbine drives a shaft and the main compressor and the supplemental EGR compressor are driven by having corresponding compressor wheels fixed onto the common shaft.

Abstract: Arrangement of a two stage turbocharger system for an internal combustion engine including an intake manifold and an exhaust manifold, including a low-pressure turbocharger, a high-pressure turbocharger and a bypass duct in flow communication with an outlet of the low-pressure compressor, an inlet of the high-pressure compressor, an outlet of the high-pressure compressor and an inlet of the intake manifold. The bypass duct includes a first bypass valve for opening and closing the bypass duct. The first bypass valve and the high-pressure compressor are accommodated within a common housing.

Abstract: A system for a sequential turbocharger includes a mode selection module, a feed-forward selection module, and a control loop module. The mode selection module generates a control mode signal based on an engine speed signal, an engine torque signal, and an engine mode signal. The control mode signal indicates one of an open-loop control mode and a closed-loop control mode. The feed-forward selection module determines a feed-forward value based on the control mode signal, the engine speed signal, and the engine torque signal. The control loop module determines a loop control value at least one of based on the feed-forward value, a variable geometry turbine (VGT) control signal, and an error signal; and based on a bypass valve (BPV) control signal and the error signal when the control mode signal transitions from the open-loop control mode to the closed-loop control mode.

Abstract: An exhaust system for a use with an engine is provided. The exhaust system may have an exhaust manifold configured to direct exhaust from the engine, and a main turbocharger connected to receive exhaust from the exhaust manifold. The exhaust system may also have a recirculation turbocharger having a compressor connected to receive exhaust from the exhaust manifold in parallel with the main turbocharger, and a turbine connected to receive exhaust from the main turbocharger to drive the compressor. The exhaust system may further have a control valve located downstream of the recirculation turbocharger to regulate exhaust flow through the compressor.

Abstract: A combustion chamber of an internal combustion engine has primary intake ports located a first distance from the crankshaft and primary intake ports located a second distance from the crankshaft. One or more unidirectional valves, such as reed valves, are place in an intake duct upstream of the primary intake ports. The valves prevent backflow from the cylinder into the intake when the pressure in the cylinder exceeds that of the intake. The backflow into the intake is reduced by having valves in the intake; therefore scavenging efficiency is improved. Furthermore, the asymmetry between the intake and exhaust port timing may be reduced by providing such valves. Additionally, the total intake port area can be increased with two sets of intake ports and valves disposed in the primary ports, thereby improving the volumetric efficiency in spite of the pressure drop presented by the valves.

Abstract: Disclosed is a pipe arrangement (1) comprising a pipe element (2) that is used to connect, in particular fluidically connect, a turbine outlet of one turbocharger (15) to a turbine inlet of another turbocharger (17). The pipe arrangement is characterized in that a first pipe section (8) of the pipe element (2) includes a first fastening device (14) for attaching a first turbocharger (15) as well as a second fastening device (20) for attaching the pipe element (2) to a first support element (21) of an internal combustion engine. Furthermore, a second pipe section (9) includes a third fastening device (16) for attaching a second turbocharger (17) as well as a fourth fastening device (24) for attaching the pipe element (2) to a second support element (25) of an internal combustion engine.

Abstract: A turbomachine system comprises a first turbocharger comprising an exhaust gas flow first turbine for location in an exhaust path and a first compressor driven by said first turbine; a turbomachine for location in the exhaust path upstream or downstream of said first turbocharger and comprising an exhaust gas flow second turbine and a second compressor driven by said second turbine. The first turbine has an outlet that is in fluid communication with an inlet of the second turbine. One of said first and second turbines is a radial outflow turbine. The arrangement provides for a relatively compact package. The radial outflow turbine may have a particular structure in which there is provided a deflector member at or near its inlet for directing the gas outwards, a stator for introducing swirl and a downstream turbine rotor. A shroud is fixed to blades of the turbine rotor to prevent leakage and to provide additional structural rigidity.

Abstract: One embodiment of the invention includes a combustion engine breathing system including a compressor valve for use with a biturbo system and cylinder deactivation.

Abstract: Method of operating an internal combustion engine, including, at least, compressing and cooling air outside an engine chamber, supplying cooled, pressurized air to an intake port associated with the chamber, and, during each engine cycle: opening the intake port, allowing cooled, pressurized air to flow through the intake port and into the chamber during at least a portion of the intake stroke; maintaining open the intake port during the portion of the intake stroke and beyond the end of the intake stroke and into the compression stroke and during a majority portion of the compression stroke; closing the intake port at a point during travel of the piston to capture in the chamber a cooled compressed charge of the cooled, pressurized air; controllably delivering fuel into the chamber after the cooled compressed charge is captured within the chamber; and igniting a fuel and air mixture within the chamber.

Abstract: In an internal combustion engine having two exhaust gas turbochargers which are connected in series and a bypass line which bypasses the exhaust gas turbine close to the engine and extends to a collecting space of the turbine remote from the engine, and a blow-off valve is integrated into the turbine housing of the remote exhaust gas turbine for controlling a communication path between the collecting space and the turbine wheel, and includes a control sleeve supported axially movably between a closed position in which the communication path is blocked and a fully open position in which a flow path by-passing the turbine wheel of the turbine remote from the engine is provided.

Abstract: An internal combustion engine control apparatus that prevents an abrupt change in the air amount at the time of supercharger switching. The control apparatus enters a small turbo operating state in which a small turbocharger is mainly operative, during relatively low-rotation-speed and low-load side, and enters a large turbo operating state in which a large turbocharger is mainly operative, in a relatively high-rotation-speed and high-load. In the small turbo operating state, the control apparatus can exercise charging efficiency enhancement control by using a scavenging effect. Before switching from the small turbo operating state to the large turbo operating state, the control apparatus predicts whether the large turbocharger will build up its boost pressure quickly or slowly. When slow boost pressure is predicted, the control apparatus exercises charging efficiency enhancement control to provide a low degree of charging efficiency enhancement.

Abstract: The intake air cooler of the invention comprises a first cooling stage (24) and a second cooling stage (26) grouped in a single heat exchanger housing (30) and sharing a common heat exchanger bundle (28) accommodated in the housing and traversed by a cooling liquid. Application to turbocharged internal combustion engines for motor vehicles.

Abstract: One embodiment is a unique system which is operable to provide a mixture of charge air and exhaust to an internal combustion intake at a sub-ambient temperature. Further embodiments, forms, objects, features, advantages, aspects, and benefits shall become apparent from the following description and drawings.

Abstract: A control device for multi-stage turbochargers is provided that is capable of improving fuel consumption in transient and stationary states of an engine equipped with multi-stage turbochargers. A control device 1 for multi-stage turbochargers which are turbochargers 6, 7 of at least two or more stages provided in series at an engine 2 and in which the high-pressure stage turbocharger 6 is configured by a variable-capacity turbocharger 6 equipped with a variable vane 64 comprising detection means 11, 12 for detecting a boost pressure or an intake air amount of a turbocharger 7 of a stage with a pressure lower than that of the variable-capacity turbocharger 6, the opening degree of the variable vane 64 being controlled on the basis of a detection value of the detection means 11, 12.

Abstract: A dual-inlet turbocharger system for internal combustion engine includes a single-shaft turbocharger with a dual-inlet compressor section. An air router provides a bifurcated air supply for the dual-inlet compressor section, and also provides a bifurcated source of charge air for the engine's cylinders in the case in which the present turbocharger system is applied to a V-block engine.

Abstract: System and methods for treating particulate matter vented from an engine crankcase are provided. In one embodiment, an engine includes a crankcase. A ventilation hose is coupled to the engine to vent a crankcase gas from the crankcase. A catalytic emissions control device is coupled to the ventilation hose to treat particulate matter in the crankcase gas.

Abstract: In a gas fueled internal combustion engine, in particular a natural gas fueled internal combustion engine, as well as in a method for fuelling an internal combustion engine with gas, in particular with natural gas, with a charged “downsizing” Otto engine and an injection of the gas, a homogenous stoichiometric gas-air mixture is set and the charging takes place by an exhaust turbo charger as well as a compressor, which can be turned off and is located above the exhaust turbo charger in the air suction route.

Abstract: The invention relates to the operation of a supercharged internal combustion engine (2) of a vehicle, wherein an air/volumetric flow current is adjusted by means of an adjustable swirl generator (8) arranged upstream of a supercharge system, taking into consideration an adjustable valve overlap of a cylinder of the internal combustion engine (2). The invention also relates to a vehicle drive comprising a supercharged internal combustion engine (2), a supercharge system of the internal combustion engine (2), an adjustable, variable valve train of the internal combustion engine (2), a control device and an adjustable swirl generator (8).

Abstract: A fluid selection valve unit comprising a valve seat having a side surface having a predetermined depth and a bottom surface continuous to the side surface and a valve member supported with a rotary shaft at one end. The valve member includes a bottom portion and a side end surface formed above the bottom portion, and is configured so that a passage area of a gap formed between the side end surface of the valve member and the side surface of the valve seat is smaller than a contact passage area formed between the bottom portion of the valve member and the bottom surface of the valve seat during a time when the bottom portion of the valve member comes into contact with the bottom surface of the valve seat by the rotation of the rotary shaft, and the rotary angle increases up to a predetermined value of the rotary angle.

Abstract: A supercharger compressor includes a plurality of rotors rotatably mounted in a housing, a first inlet for air, a second inlet for recirculated exhaust gas, and a flow separator. The flow separator is arranged interior the housing and configured to form a slideable seal with at least one rotor of the plurality of rotors, the slideable seal fluidically isolating the first inlet from the second inlet, at least in part, and retarding pressure equalization therebetween.

Abstract: A system for recovering engine exhaust energy is provided. The system includes an exhaust system including a first exhaust branch and a second exhaust branch. The system includes a first and a second group of exhaust valves associated with a plurality of engine cylinders. The system also includes an energy recovering assembly. The system further includes a control mechanism configured to control at least one of the first and second groups of exhaust valves according to a determined timing strategy based on at least one engine operating parameter.

Abstract: An internal combustion engine having a reciprocating multi cylinder internal combustion engine with multiple valves. At least a pair of exhaust valves are provided and each supply a separate power extraction device. The first exhaust valves connect to a power turbine used to provide additional power to the engine either mechanically or electrically. The flow path from these exhaust valves is smaller in area and volume than a second flow path which is used to deliver products of combustion to a turbocharger turbine. The timing of the exhaust valve events is controlled to produce a higher grade of energy to the power turbine and enhance the ability to extract power from the combustion process.

Abstract: An internal combustion engine is disclosed, comprising at least one first compression device and at least one second compression device which is connected in series relative to the first compression device. At least one bypass pipe bypasses at least one compression device. At least one controllable valve is arranged in the at least one bypass pipe such that the amount of fluid which can be recirculated around the compression device can be controlled.

Abstract: A sequential-type, two-stage supercharging system (1) having a high-pressure-stage turbocharger (6) and a low-pressure-stage turbocharger (5), in which high-pressure-stage exhaust gas bypass passages (6d, 6e) for bypassing a high-pressure-stage turbine (6t) is formed by both the first bypass passage (6d) having a small-diameter valve (6f) and the second bypass passage (6e) having a large-diameter valve (6g) with a diameter greater than that of the small-diameter valve (6f). The effective valve area of the small-diameter valve (6f) is set to 9.5%-26.5% of the passage cross-sectional area required when exhaust gas is at its maximum total flow rate. This allows, in medium speed/medium load operation, fine EGR rate control and air-fuel ratio control.

Abstract: A multistage exhaust turbocharger is easily mountable in a narrow engine compartment of a vehicle by simplifying its construction and reducing its bulk. The multistage exhaust turbocharger has a high-pressure stage turbocharger and a low-pressure stage turbocharger. A cover of the high-pressure stage turbocharger has a compressor inlet passage, a bypass inlet passage, a switching aperture between the passages to be opened and closed by a valve body of the compressor bypass valve device, and a bypass outlet pipe part connecting to the bypass inlet passage to introduce bypass air passed through the aperture opened by the bypass valve to the compressor bypass channel which is to be connected to the bypass outlet pipe part.

Abstract: A turbocharger system comprises a first relatively small high-pressure (HP) turbocharger (1) and a second relatively large low pressure (LP) turbocharger (2). The turbine (6) of the LP turbocharger (2) is connected in series downstream of the turbine (4) of the HP turbocharger (1) in a first exhaust gas passage (11). An exhaust bypass flow passage (12) provides a bypass flow path around the HP turbine (4). A rotary valve (8) is located at a junction of the bypass flow passage (12) and a first exhaust gas flow passage (11). The rotary valve (8) comprises a valve rotor (19) which is rotatable to selectively permit or block flow to the LP turbine (6) from either the first exhaust gas passage (11) or the bypass gas passage (12). The rotary valve (8) is operated to at least partially restrict flow to the LP turbine to generate a braking back pressure.

Abstract: An apparatus, system, and method are disclosed for a single-actuated multi-function valve. The apparatus includes a primary fluid conduit, a secondary fluid conduit, and a valve. The primary fluid conduit flows from an exhaust manifold to an outlet through a high pressure turbocharger and a low pressure turbocharger. The secondary fluid conduit flows from the exhaust manifold to an outlet through the low pressure turbocharger. The valve has two flow passages—the first flow passage is a variable restriction within the primary fluid conduit, and the second flow passage is a variable restriction within the secondary fluid conduit. Turning the valve one direction from a nominal position controls the flow ratios in the primary and secondary fluid conduits, while turning the valve in the other direction from the nominal position controls exhaust braking.

Abstract: An engine system for a vehicle is provided, comprising an internal combustion engine including an exhaust system; a first turbine including a first wastegate and arranged along a first branch of the exhaust system, a second turbine including a second wastegate and arranged along a second branch of the exhaust system; a first exhaust gas sensor arranged along the first branch of the exhaust system downstream of the first turbine and first wastegate; a second exhaust gas sensor arranged along the second branch of the exhaust system downstream of the second turbine and the second wastegate; and a control system configured to command the first and second wastegates to a closed or open position and to indicate one of said wastegates as unresponsive to said command in response to a temperature difference between the first and second branches indicated by the first and second exhaust gas sensors.

Abstract: A method for estimating the output temperature of the output compressor of a two-stage turbocharger. The method includes: storing a composite relationship relating temperature ratio across a pair of compressors of the two-stage turbocharger as a function of mass flow through such pair of compressors and pressure drop across the pair of the compressors; calculating the pressure ratio equal to the pressure at an input to the first one of the pair of compressors to the pressure at the output of the second one of the pair compressor; using the composite relationship and an output of a mass flow at the input to the first one of the pair of compressors and the calculated pressure ratio to determine the temperature ratio across the pair of compressors; and calculating the estimated output temperature of the second one of the pair of compressors by multiplying the determined temperature ratio across the pair of compressors by a temperature at the input of the first one of the pair of compressors.

Abstract: An apparatus, system, and method are disclosed for preventing overspeed of a turbocharger. The apparatus includes a two-stage turbocharger system with a high pressure and a low pressure turbocharger. A bypass valve that divides an exhaust flow into a primary exhaust flow and a bypass flow. A relief valve vents a portion of the primary exhaust flow around the high pressure turbocharger. The low pressure turbocharger receives the bypass flow, the primary exhaust flow, and the vented portion of the primary exhaust flow. The apparatus includes a controller having a protection condition module that determines a protection indicator, and a relief valve control module that controls the relief valve according to the protection indicator.

Abstract: An internal combustion engine includes a number of power cylinders furnishing exhaust gases to at least two turbochargers having a common air inlet housing which is divided into a separate compressor housing for each of the turbochargers.

Abstract: A supercharger control device for an internal combustion engine is preferably applied to a system having a first supercharger and a second supercharger. A switching supercharging pressure setting unit sets a switching supercharging pressure used in case of switching a mode for operating the first supercharger and the second supercharger, based on a difference between a target supercharging pressure and an actual supercharging pressure. When the actual supercharging pressure reaches the switching supercharging pressure, a switching control unit performs a control of switching the mode. Therefore, it becomes possible to appropriately prevent the overshoot of the supercharging pressure at the time of switching the mode.

Abstract: The invention concerns turbochargers, or more particularly to multivariable dual stage series turbochargers having two degrees of freedom. A multistage series turbocharger apparatus has a low pressure turbocharger comprising a low pressure compressor and a low pressure turbine; a high pressure turbocharger comprising a high pressure compressor and a high pressure turbine, and a exhaust gas recirculation device. A controller controls the operation of at least two of the low pressure compressor, high pressure compressor, low pressure turbine, high pressure turbine, and exhaust gas recirculation device such that at least one operating parameter is maintained at about a selected value.

Abstract: A turbo charge system of an engine minimizes energy loss of exhaust gas as a consequence of a crossover pipe that connects exhaust manifolds respectively mounted to cylinder heads at both sides of the engine with each other and that is mounted in each cylinder head, and the crossover pipe is formed as a double pipe structure. The turbo charge system of the engine may include a pair of exhaust manifolds respectively mounted to cylinder heads at both sides of the engine; a pair of turbo chargers connected respectively to the pair of exhaust manifolds and increasing intake air amount by using energy of exhaust gas; and a crossover pipe connecting the pair of exhaust manifolds with each other, wherein a crossover pipe is mounted in each cylinder head.

Abstract: A twin turbo assembly is provided for an automotive vehicle that includes, but is not limited to a first air intake for sucking in ambient air, a first turbo charger that includes, but is not limited to a first compressor connected to the first air intake, a first intake duct connecting the first turbo charger to a combustion engine, a second air intake for sucking in ambient air, a second turbo charger that includes, but is not limited to a second compressor connected to the second air intake, and a second intake duct connecting the second turbo charger to the combustion engine. The first intake duct is connected to the second intake duct, and a first bypass valve is provided to connect the first air intake to the first intake duct bypassing the first compressor and/or a second bypass valve is provided to connect the second air intake to the second intake duct bypassing the second compressor.

Abstract: A method for improving turbocharger waste-gate control is presented. The method can reduce turbocharger flow oscillation, at least during some conditions.

Abstract: For an internal combustion engine having two cylinder banks forming a V-shaped cylinder block, a turbocharger system including a high pressure turbocharger disposed in a valley between the cylinder banks, a first low-pressure turbocharger disposed adjacent an outer side of one of the cylinder banks, and a second low-pressure turbocharger disposed adjacent an outer side of the second cylinder bank. Intake and exhaust ducts connect the components of the engine and turbocharger system to and electronically controlled valves associated with the ducts permit the system to operate either in a split series mode or a low-pressure-only mode.

Abstract: A method and a system for cooling an internal combustion engine having charge air feed, which has a first and a second cooling loop, of which the first cooling loop is operated at a higher temperature level than the second cooling loop, and in which the charge air feed has at least one intercooling unit which is thermally coupled to the second cooling loop, having a controllable coolant throughput. The system includes at least one shutdown element in the second cooling loop for throttling the coolant throughput in the second cooling loop to 0 (zero). Coolant throughput may be shut down during the operation of the internal combustion engine as a function of an operating parameter of a vehicle component.

Abstract: A two-volute low pressure turbocharger is provided with a VGT mechanism in one turbine volute only.

Abstract: An internal combustion engine control apparatus that prevents an abrupt change in the air amount at the time of supercharger switching. The control apparatus enters a small turbo operating state in which a small turbocharger is mainly operative, during relatively low-rotation-speed and low-load side, and enters a large turbo operating state in which a large turbocharger is mainly operative, in a relatively high-rotation-speed and high-load. In the small turbo operating state, the control apparatus can exercise charging efficiency enhancement control by using a scavenging effect. Before switching from the small turbo operating state to the large turbo operating state, the control apparatus predicts whether the large turbocharger will build up its boost pressure quickly or slowly. When slow boost pressure is predicted, the control apparatus exercises charging efficiency enhancement control to provide a low degree of charging efficiency enhancement.

Abstract: The invention relates to an internal combustion engine, especially of a motor vehicle, which comprises an air path for intake air in which a mechanically driven charge unit (20), especially a compressor, which can be connected and disconnected by means of a coupling (36), an exhaust gas turbocharger (18), an intake pipe (32), connected to air inlets of a cylinder block (10) of the internal combustion engine, and a charge cooler (34) are mounted. One pressure outlet (35) of the mechanically driven charge unit (20 is directly connected to the intake pipe (32) and one pressure outlet (24) of the exhaust gas charger (18) is connected to an intake inlet (28) of the mechanically driven charge unit (20). The pressure outlet (24) of the exhaust gas charger (18) is connected to the intake inlet (28) of the mechanically driven charge unit (20) via an on-off butterfly valve (26) and upstream of said on-off butterfly valve (26) to the intake pipe (32) via a load butterfly valve (30).

Abstract: A method is described for controlling the exhaust temperature of an emission controlling device in the exhaust using both a higher heat loss path and a lower heat loss path along with parallel/sequential turbocharging. The exhaust path is adjusted based on a rate of change of temperature control error.

Abstract: An internal combustion engine (100) includes a first exhaust manifold (120), and a second exhaust manifold (118) fluidly connected to the first exhaust manifold (120) through an exhaust valve (122). An exhaust gas recirculation (EGR) cooler (124) constantly fluidly connects the second exhaust manifold (118) with an intake manifold (112). A turbocharger (102) has a turbine (126) in fluid communication with the first exhaust manifold (120), and a compressor (132) in fluid communication with a supercharger (140). A charge air cooler (150) fluidly connects the supercharger (140) with the intake manifold (112).

Abstract: The invention provides a 2-stroke internal combustion engine comprising two opposed cylinders, each cylinder housing two opposed pistons and having at least one exhaust port and at least one intake port, and a crankshaft having asymmetrically arranged journals and scotch-yoke mechanisms for driving the journals from the pistons. The pistons in each cylinder operate to open its exhaust port or ports before its intake port or ports and to close its exhaust port or ports before its intake port or ports.