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28-577: The TVR Speed Six was the name of a naturally aspirated straight-6 engine manufactured from 1999 to 2007 by British car manufacturer TVR , and used in several of their cars including the Tuscan , Cerbera , Tamora , T350 , Sagaris and Typhon . The engine's prototypes (referred to as AJP-6) were designed and delivered by independent engineer Al Melling (the "A" in AJP) as both 3.0 and 3.5 litre units. Many of its key cylinder head design elements (particularly

56-546: A dry sump lubrication system allowing the engine to be mounted lower in the vehicle chassis. These features enabled the engine to provide lightweight, compact dimensions, extremely fast throttle response and high peak horsepower. In order to reduce unit production costs, the engines that actually went into production, called Speed Six , were TVR modified versions of the initial AJP-6 prototypes with 3.6 litres (3,605 cc) and 4.0 litres (3,996 cc) capacities. Prominent modifications were alterations to valve train geometry,

84-527: A gasoline engine approximates a constant volume process during that phase. The image shows a p–V diagram for the ideal Diesel cycle; where p {\displaystyle p} is pressure and V the volume or v {\displaystyle v} the specific volume if the process is placed on a unit mass basis. The idealized Diesel cycle assumes an ideal gas and ignores combustion chemistry, exhaust- and recharge procedures and simply follows four distinct processes: The Diesel engine

112-470: A less than complete air charge in the cylinder. The density of the air charge, and therefore the engine's maximum theoretical power output , in addition to being influenced by induction system restriction, is also affected by engine speed and atmospheric pressure, the latter of which decreases as the operating altitude increases. This is in contrast to a forced-induction engine, in which a mechanically driven supercharger or an exhaust-driven turbocharger

140-406: A more favourable power-to-weight ratio , a higher torque curve , as well as better fuel efficiency and lower exhaust emissions . Turbocharging is nearly universal on diesel engines that are used in railroad , marine engines , and commercial stationary applications ( electrical power generation , for example). Forced induction is also used with reciprocating aircraft engines to negate some of

168-490: A petrol engine were to have the same compression ratio, then knocking (self-ignition) would occur and this would severely reduce the efficiency, whereas in a diesel engine, the self ignition is the desired behavior. Additionally, both of these cycles are only idealizations, and the actual behavior does not divide as clearly or sharply. Furthermore, the ideal Otto cycle formula stated above does not include throttling losses, which do not apply to diesel engines. Diesel engines have

196-582: A switch from a billet steel crank to cast iron (with a crank damper), different connecting rods , oil filter relocation to the inlet side of the engine, and removal of the exhaust cam oil feed. The two different capacities were achieved through stroke alterations from a con-rod design able to accommodate two different stroke lengths, and different piston crown designs altering the compression ratios . The bore diameters were shared. Pistons were made in Italy by Asso Werke from pre-existing casts, initially designed for

224-566: Is 36.3% available oxygen by mass after it decomposes as compared with atmospheric air at 20.95%. Nitrous oxide also boils at −127.3 °F (−88.5 °C) at atmospheric pressures and offers significant cooling from the latent heat of vaporization, which also aids in increasing the overall air charge density significantly compared to natural aspiration. Most automobile petrol engines, as well as many small engines used for non-automotive purposes, are naturally aspirated. Most modern diesel engines powering highway vehicles are turbocharged to produce

252-493: Is a heat engine: it converts heat into work . During the bottom isentropic processes (blue), energy is transferred into the system in the form of work W i n {\displaystyle W_{in}} , but by definition (isentropic) no energy is transferred into or out of the system in the form of heat. During the constant pressure (red, isobaric ) process, energy enters the system as heat Q i n {\displaystyle Q_{in}} . During

280-411: Is also called the useful work, as it can be turned to other useful types of energy and propel a vehicle ( kinetic energy ) or produce electrical energy. The summation of many such cycles per unit of time is called the developed power. The W o u t {\displaystyle W_{out}} is also called the gross work, some of which is used in the next cycle of the engine to compress

308-435: Is at constant pressure and the heat rejection is at constant volume. The Otto cycle by comparison has both the heat addition and rejection at constant volume. Comparing the two formulae it can be seen that for a given compression ratio ( r ), the ideal Otto cycle will be more efficient. However, a real diesel engine will be more efficient overall since it will have the ability to operate at higher compression ratios. If

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336-415: Is drawn into the engine's cylinders by atmospheric pressure acting against a partial vacuum that occurs as the piston travels downwards toward bottom dead centre during the intake stroke . Owing to innate restriction in the engine's inlet tract, which includes the intake manifold , a small pressure drop occurs as air is drawn in, resulting in a volumetric efficiency of less than 100 percent—and

364-408: Is employed to facilitate increasing the mass of intake air beyond what could be produced by atmospheric pressure alone. Nitrous oxide can also be used to artificially increase the mass of oxygen present in the intake air. This is accomplished by injecting liquid nitrous oxide into the intake, which supplies significantly more oxygen in a given volume than is possible with atmospheric air. Nitrous oxide

392-508: Is more complex than the Otto cycle (petrol/gasoline engine) relation that has the following formula: η o t t o , t h = 1 − 1 r γ − 1 {\displaystyle \eta _{otto,th}=1-{\frac {1}{r^{\gamma -1}}}} The additional complexity for the Diesel formula comes around since the heat addition

420-692: The Rotax - Aprilia RSV 1000 engine. Those casts, refused by Rotax, were modified and used to produce the smaller Speed Six pistons. Unfortunately, during TVR’s development of the original MCD design, it was decided to remove the drilled lubrication oil-ways from the camshaft centres to the peak of each of the camshaft lobes, resulting in starvation of lubrication and early versions of the Speed Six engine suffering from poor valve-train durability leading to many warranty claims against TVR. German and French tuners and owners have, since, re-introduced these oil-ways, returning

448-437: The valvetrain ) were first seen in the 1991 Suzuki GSX-R750 (M) motorcycle engine (also a Melling design). The key design features were an all aluminium alloy block and head, with cast iron cylinder liners , double overhead camshafts , finger follower 24-valve actuation, one throttle and injector per cylinder ( throttle-body fuel injection ), equal length tubular exhaust manifolds dual 3-way catalytic converters and

476-536: The Typhon/T440 model. However this proved unsuccessful due to cooling challenges so the few Typhon/T440 models that made production were instead fitted with standard naturally aspirated 4.0L Speed Six engines. Naturally aspirated In a naturally aspirated engine, air for combustion ( Diesel cycle in a diesel engine or specific types of Otto cycle in petrol engines, namely petrol direct injection ) or an air/fuel mixture (traditional Otto cycle petrol engines),

504-399: The combustion chamber, into which fuel is then injected. This is in contrast to igniting the fuel-air mixture with a spark plug as in the Otto cycle ( four-stroke /petrol) engine. Diesel engines are used in aircraft , automobiles , power generation , diesel–electric locomotives , and both surface ships and submarines . The Diesel cycle is assumed to have constant pressure during

532-464: The engine as used in the Cerbera produced 350 bhp (355 PS; 261 kW) with the final incarnations of the engine having TVR claimed outputs of 406 bhp (412 PS; 303 kW) in the Tuscan S , Sagaris and Typhon . TVR further developed the Speed Six into the limited-production V12 Speed Twelve racing engine. TVR also experimented with supercharging the Speed Six engine for use in

560-528: The flame temperature of the fuel used. The flame temperature can be approximated to the adiabatic flame temperature of the fuel with corresponding air-to-fuel ratio and compression pressure, p 3 {\displaystyle p_{3}} . T 1 {\displaystyle T_{1}} can be approximated to the inlet air temperature. This formula only gives the ideal thermal efficiency. The actual thermal efficiency will be significantly lower due to heat and friction losses. The formula

588-449: The initial part of the combustion phase ( V 2 {\displaystyle V_{2}} to V 3 {\displaystyle V_{3}} in the diagram, below). This is an idealized mathematical model: real physical diesels do have an increase in pressure during this period, but it is less pronounced than in the Otto cycle. In contrast, the idealized Otto cycle of

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616-595: The low-stress, high-efficiency cycle leads to much longer engine life and lower operational costs. These advantages also make the diesel engine ideal for use in the heavy-haul railroad and earthmoving environments. Many model airplanes use very simple "glow" and "diesel" engines. Glow engines use glow plugs . "Diesel" model airplane engines have variable compression ratios. Both types depend on special fuels. Some 19th-century or earlier experimental engines used external flames, exposed by valves, for ignition, but this becomes less attractive with increasing compression. (It

644-489: The lowest specific fuel consumption of any large internal combustion engine employing a single cycle, 0.26 lb/hp·h (0.16 kg/kWh) for very large marine engines (combined cycle power plants are more efficient, but employ two engines rather than one). Two-stroke diesels with high pressure forced induction, particularly turbocharging , make up a large percentage of the very largest diesel engines. In North America , diesel engines are primarily used in large trucks, where

672-403: The motor to its original, efficient and reliable design. Other third party development work has also mitigated this issue by using revised material hardness for the cam lobes, finger followers and valve guides. Softer valve springs and valves with thicker stems were also utilised. Engines that have had these modifications performed have also improved durability. The initial 4.0 litre version of

700-764: The next charge of air. The maximum thermal efficiency of a Diesel cycle is dependent on the compression ratio and the cut-off ratio. It has the following formula under cold air standard analysis: η t h = 1 − 1 r γ − 1 ( α γ − 1 γ ( α − 1 ) ) {\displaystyle \eta _{th}=1-{\frac {1}{r^{\gamma -1}}}\left({\frac {\alpha ^{\gamma }-1}{\gamma (\alpha -1)}}\right)} where The cut-off ratio can be expressed in terms of temperature as shown below: T 3 {\displaystyle T_{3}} can be approximated to

728-405: The power loss that occurs as the aircraft climbs to higher altitudes. The advantages and disadvantages of a naturally aspirated engine in relation to a same-sized engine relying on forced induction include: Diesel cycle The Diesel cycle is a combustion process of a reciprocating internal combustion engine . In it, fuel is ignited by heat generated during the compression of air in

756-419: The system is equal to the work that enters the system plus the difference between the heat added to the system and the heat that leaves the system; in other words, net gain of work is equal to the difference between the heat added to the system and the heat that leaves the system. The net work produced is also represented by the area enclosed by the cycle on the p–V diagram. The net work is produced per cycle and

784-518: The top isentropic processes (yellow), energy is transferred out of the system in the form of W o u t {\displaystyle W_{out}} , but by definition (isentropic) no energy is transferred into or out of the system in the form of heat. During the constant volume (green, isochoric ) process, some of the energy flows out of the system as heat through the right depressurizing process Q o u t {\displaystyle Q_{out}} . The work that leaves

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