A variety of methods and arrangements for improving the fuel efficiency of internal combustion engines based on skip fire operation of the engine are described. In one aspect the skip fire decisions are made on a working cycle by working cycle basis. During selected skipped working cycles, the corresponding cylinders are deactivated such that air is not pumped through the cylinder during the selected skipped working cycles. In some implementations, the cylinders are deactivated by holding associated intake and exhaust valves closed such that an air charge is not present in the working chamber during the selected skipped working cycles.

A combined-cycle combustion control type three-cylinder engine includes: a cylinder block; and cylinders arranged in a row in the cylinder block and consisting of first, second, and third cylinders so that four-cycle combustion is performed in two of the first, second, and third cylinders and two-cycle combustion is performed in the remaining cylinder. A crankshaft is provided in first, second, and third pistons and converting reciprocating motions of the respective first, second, and third cylinders into rotational motions. A camshaft receives a rotational force from the crankshaft to control intake and exhaust timings for each of the first, second, and third cylinders.

A utility engine air-to-fuel ratio control method in which during an initial or early part of a period of engine continuous operation its stability of operation is determined and if sufficiently stable a test of the air-to-fuel ratio of the air-fuel mixture supplied to the engine is performed and if need be changed to a new air-to-fuel ratio supplied to the engine during the remainder of the period of engine continuous operation. If the engine operation is not sufficiently stable the test is not started or if started is aborted.

Methods and systems for supplying fuel to a diesel engine during a cycle of a cylinder are described. In one example, a cylinder is supplied fuel via two fuel injectors having different fuel flow rates. The two fuel injectors may be operated to provide pilot, main, and post combustion fuel injections during a cycle of a cylinder.

An engine system for a vehicle includes an engine comprising X cylinders (X4) and Y deactivation mechanisms (X/2<Y<X), each of the Y deactivation mechanisms being configured to deactivate a different one of the X cylinders and wherein the Y deactivation mechanisms are arranged an optimal Y of the X cylinders for a defined firing order of the X cylinders. The engine system further includes a controller configured to: determine a torque request for the engine, determine a set of potential firing fractions of the engine, each firing fraction representing a particular Z of the X cylinders being deactivated (0<ZY) based on the torque request, determine an optimal firing fraction of the set of potential firing fractions, based on the optimal firing fraction, command a corresponding Z of the Y deactivation mechanisms to deactivate the determined Z of the X cylinders, and command firing of a remainder the X cylinders.

A drive train for a motor vehicle includes an internal combustion engine, a starting device, and a vibration isolation device. The internal combustion engine has a main order of vibration and an excitation frequency predetermined by a predetermined operating principle and a predetermined number of cylinders. The starting device is for starting the internal combustion engine and has an electric machine with a torque characteristic over a speed (n). The vibration isolation device is designed for the main order of vibration of the internal combustion engine. The vibration isolation device has a resonance characteristic below an idling speed (nL) of the internal combustion engine in a resonance range occurring in a first speed range (n2). The resonance range is shifted into a second, lower speed range (n1 when the electric machine is coupled. The electric machine is arranged to supply a torque effective beyond the second, lower speed range (n1.).

A four-stroke internal combustion engine is disclosed comprising an exhaust valve control arrangement with an exhaust valve phase-shifting device configured to phase-shift control of the at least one exhaust valve to a state where the at least one exhaust valve is controlled in such a way that it is opened during the expansion stroke of the engine and closed during the exhaust stroke of the engine, in order to achieve engine-braking via compression in the cylinders during the exhaust stroke. An inlet valve control arrangement comprises an inlet valve phase-shifting device configured to regulate the amount of air pumped through the engine during the engine braking by regulating the phase-shift of the at least one inlet valve. The present disclosure also relates to a vehicle comprising an engine and method of controlling an engine, a computer program and a computer program for performing a method of controlling an engine.

An engine torque estimator for an internal combustion engine, includes a cylinder internal pressure sensor, an indicated-torque calculator, a pump loss torque calculator, and an engine torque calculator. The cylinder internal pressure sensor detects a cylinder internal pressure in a cylinder. The indicated-torque calculator calculates an indicated torque in a second combustion cycle based on the cylinder internal pressure detected in a period from an exhaust stroke in a first combustion cycle to an expansion stroke in the second combustion cycle. The second combustion cycle that follows the first combustion cycle. The pump loss torque calculator calculates a pump loss torque in the second combustion cycle based on the cylinder internal pressure detected in the period. The engine torque calculator calculates an engine torque of the internal combustion based on the indicated torque and the pump loss torque.

A variety of methods and arrangements for improving the fuel efficiency of internal combustion engines based on skip fire operation of the engine are described. In one aspect the skip fire decisions are made on a working cycle by working cycle basis. During selected skipped working cycles, the corresponding cylinders are deactivated such that air is not pumped through the cylinder during the selected skipped working cycles. In some implementations, the cylinders are deactivated by holding associated intake and exhaust valves closed such that an air charge is not present in the working chamber during the selected skipped working cycles.

Systems and methods for operating an engine in a variety of different cylinder operating modes are presented. In one example, an actual total number of available cylinder modes is increased in response to a vehicle's suspension setting and road roughness. By increasing the available cylinder modes, the engine may be operated in a higher number of modes where one or more engine cylinders may be deactivated to conserve fuel. The number of cylinder modes is increased during conditions where vehicle occupants may be less likely to object to operating the engine with fewer active cylinders.