In an internal combustion engine, the geometry of the exhaust system can be optimised ("tuned") to maximise the power output of the engine. Tuned exhausts are designed so that reflected pressure waves arrive at the exhaust port at a particular time in the combustion cycle.
In two-stroke engines where the exhaust port is opened by being uncovered by the piston (rather than by a separate valve), a tuned exhaust system usually consists of an expansion chamber. The expansion chamber is designed to produce a negative pressure wave to assist in filling the cylinder with the next intake charge, and then to produce a positive pressure wave which reduces the amount of fresh intake charge that escapes through the exhaust port (port blocking).
An alternate design of two-stroke engines is where the exhaust port is opened/closed using a poppet valve and the intake port is piston-controlled (opened by being uncovered by the piston). The timing of the exhaust valve closure is designed to assist in filling the cylinder with the next intake charge (as per four-stroke engines).
An opposed piston engine uses uniflow scavenging, however this design uses piston-controlled cylinder ports with one piston controlling the inlet port and the other the exhaust port. Similarly, split-single engines use uniflow scavenging, with the piston in one cylinder controlling the transfer port (where the intake mixture enters the cylinder) and the other piston controls the exhaust port.
In a four-stroke engine, an exhaust manifold which is designed to maximise the power output of an engine is often called "extractors" or "headers". The pipe lengths and merging locations are designed to assist in filling the cylinder with the next intake charge using exhaust scavenging. [1] Locations where exhaust pipes from individual cylinders merge are called "collectors". The diameters of the exhaust system are designed to minimise back-pressure by optimising the gas velocity.
Extractors/headers usually have equal length pipes for each cylinder, whereas a more basic exhaust manifold may have unequal length pipes.
A 4-2-1 exhaust system is a type of exhaust manifold for an engine with four cylinders per bank, such as an inline-four engine or a V8 engine. The layout of a 4-2-1 system is as follows: four pipes (primary) come off the cylinder head, and merge into two pipes (secondary), which in turn finally link up to form one collector pipe. [2]
Compared with a 4-1 exhaust system, a 4-2-1 often produces more power at mid-range engine speeds (RPM), while a 4-1 exhaust produces more power at high RPM. [3] [4]
The purpose of a 4-2-1 exhaust system is to increase scavenging by merging the exhaust paths of specific pairs of cylinders. Therefore, the cylinder pairings are defined by the intervals between firing events, which is determined by the firing order and— for engines with an unevenly spaced firing order— the firing interval.
For an inline-four engine with a typical firing order of 1-3-4-2, pairing cylinders 1 & 4 and cylinders 2 & 3 is considered "non-sequential", since the paired cylinders do not follow each other in the firing order. This non-sequential arrangement results in an even spacing of 360 degrees between the firing interval in each cylinder pair. A sequential pairing would result in uneven spacings, such as 180 degrees and 540 degrees for pairings of cylinders 1 & 2 and 3 & 4. This sequential pairing is used by many motorcycle engines.[ citation needed ]
For a V8 engine with a typical crossplane design, 4-2-1 exhausts are often called "Tri-Y" exhausts. Traditionally, only cylinders within the same bank were paired, resulting in spacings of 90-630 degrees (sequential), 180-540 degrees or 270-450 degrees. Typically, the 270 interval is favoured, requiring different pairings in each bank; e.g. 1 & 2 and 3 & 4 in one bank, but 1 & 3 and 2 & 4 in the other. Naturally, such exhausts are sensitive to the specific firing order in use. [5] [6] Even spacings of 360-360 degrees are only possible if a cross-over exhaust manifold is used to pair cylinders from separate banks.
The combining of exhaust pressure pulses from each cylinder dictates the lengths of the pipes necessary. Generally, shorter pipes will help produce more power at higher engine rpm, and longer pipes favour low-rpm torque, thereby altering the power band. [7] However, the gases tend to cool as they pass through longer pipes, which reduces the effectiveness of the catalytic converter.
In a turbocharged engine, the key factor in the length of the exhaust pipes is providing evenly-spaced pressure pulses to the turbine of the turbocharger. [5]
Two-stroke engines | Four-stroke engines |
A two-strokeengine is a type of internal combustion engine that completes a power cycle with two strokes of the piston during one power cycle, this power cycle being completed in one revolution of the crankshaft. A four-stroke engine requires four strokes of the piston to complete a power cycle during two crankshaft revolutions. In a two-stroke engine, the end of the combustion stroke and the beginning of the compression stroke happen simultaneously, with the intake and exhaust functions occurring at the same time.
The Napier Deltic engine is a British opposed-piston valveless, supercharged uniflow scavenged, two-stroke diesel engine used in marine and locomotive applications, designed and produced by D. Napier & Son. Unusually, the cylinders were disposed in a three-bank triangle, with a crankshaft at each corner of the triangle.
The GM High Feature engine is a family of modern DOHC V6 engines produced by General Motors. The series was introduced in 2004 with the Cadillac CTS and the Holden Commodore (VZ).
In automotive engineering, an exhaust manifold collects the exhaust gases from multiple cylinders into one pipe. The word manifold comes from the Old English word manigfeald and refers to the folding together of multiple inputs and outputs.
In automotive engineering, an inlet manifold or intake manifold is the part of an engine that supplies the fuel/air mixture to the cylinders. The word manifold comes from the Old English word manigfeald and refers to the multiplying of one (pipe) into many.
The Lamborghini V10 is a ninety degree (90°) V10 petrol engine which was developed for the Lamborghini Gallardo automobile, first sold in 2003.
Alfa Romeo Twin Spark (TS) technology was used for the first time in the Alfa Romeo Grand Prix car in 1914. In the early 1960s it was used in their race cars (GTA, TZ) to enable it to achieve a higher power output from its engines. And in the early and middle 1980s, Alfa Romeo incorporated this technology into their road cars to enhance their performance and to comply with stricter emission controls.
An exhaust system is used to guide reaction exhaust gases away from a controlled combustion inside an engine or stove. The entire system conveys burnt gases from the engine and includes one or more exhaust pipes. Depending on the overall system design, the exhaust gas may flow through one or more of:
The Honda F-Series engine was considered Honda's "big block" SOHC inline four, though lower production DOHC versions of the F-series were built. It features a solid iron or aluminum open deck cast iron sleeved block and aluminum/magnesium cylinder head.
The crossplane or cross-plane is a crankshaft design for piston engines with a 90° angle between the crank throws. The crossplane crankshaft is the most popular configuration used in V8 road cars.
Twin-turbo refers to an engine in which two turbochargers work in tandem to compress the intake fuel/air mixture. The most common layout features two identical or mirrored turbochargers in parallel, each processing half of a V engine's produced exhaust through independent piping. The two turbochargers can either be matching or different sizes.
In engine technology, a reverse-flow or non-crossflow cylinder head is one that locates the intake and exhaust ports on the same side of the engine. The gases can be thought to enter the cylinder head and then change direction to exit the head. This is in contrast to the crossflow cylinder head design.
In a spark ignition internal combustion engine, ignition timing is the timing, relative to the current piston position and crankshaft angle, of the release of a spark in the combustion chamber near the end of the compression stroke.
Scavenging is the process of replacing the exhaust gas in a cylinder of an internal combustion engine with the fresh air/fuel mixture for the next cycle. If scavenging is incomplete, the remaining exhaust gases can cause improper combustion for the next cycle, leading to reduced power output.
A two-stroke diesel engine is a diesel engine that uses compression ignition in a two-stroke combustion cycle. It was invented by Hugo Güldner in 1899.
The VR5 engines are a family of petroleum fuelled Internal combustion engines developed by the Volkswagen Group and produced from 1997 to 2006. They are derived from the VR6 engine family, also developed by Volkswagen, but with one less cylinder. The VR5 is a highly compact, thanks to the narrower angle of 15° and a displacement of 2,324 cc. The VR5 was the first production block to use five cylinders in a VR design with a 15-degree angle.
The Honda P engine is an inline three-cylinder gasoline engine first designed for use in Honda kei cars. The P engine was first used in the fourth generation Honda Life, as a successor to the Honda E07A engine. The P engine series was initially produced in only one displacement variant: 658 cc, either naturally aspirated or turbocharged. A turbocharged one-litre version, the P10A, has since been developed. The smaller version was discontinued in December 2013, when it was replaced by the new S07 series engine, but the P10A continues to be built in Thailand.
An internal combustion engine is a heat engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies direct force to some component of the engine. The force is typically applied to pistons, turbine blades, a rotor, or a nozzle. This force moves the component over a distance, transforming chemical energy into kinetic energy which is used to propel, move or power whatever the engine is attached to.
The Volkswagen-Audi V8 engine family is a series of mechanically similar, gasoline-powered and diesel-powered, V-8, internal combustion piston engines, developed and produced by the Volkswagen Group, in partnership with Audi, since 1988. They have been used in various Volkswagen Group models, and by numerous Volkswagen-owned companies. The first spark-ignition gasoline V-8 engine configuration was used in the 1988 Audi V8 model; and the first compression-ignition diesel V8 engine configuration was used in the 1999 Audi A8 3.3 TDI Quattro. The V8 gasoline and diesel engines have been used in most Audi, Volkswagen, Porsche, Bentley, and Lamborghini models ever since. The larger-displacement diesel V8 engine configuration has also been used in various Scania commercial vehicles; such as in trucks, buses, and marine (boat) applications.