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29-400: D800 may refer to: British Rail Class 43 (Warship Class) , a locomotive Dell Latitude D800 , a laptop computer Nikon D800 , a full-frame digital single-lens reflex camera Samsung D800 , slider phone [REDACTED] Topics referred to by the same term This disambiguation page lists articles associated with the same title formed as

58-453: A function of engine speed. This ensures good low to mid-range performance. At low engine speeds the wave pressure within the pipe network is low. A full oscillation of the Helmholtz resonance occurs before the exhaust valve is closed, and to increase low-speed torque, large amplitude exhaust pressure waves are artificially induced. This is achieved by partial closing of an internal valve within

87-479: A gain in power output. The processes occurring can be explained by the gas laws , specifically the ideal gas law and the combined gas law . When an engine starts its exhaust stroke, the piston moves up the cylinder bore, decreasing the total chamber volume. When the exhaust valve opens, the high pressure exhaust gas escapes into the exhaust manifold or header, creating an "exhaust pulse" comprising three main parts: This relatively low pressure helps to extract all

116-403: A greater pressure difference between the high pressure head of the next exhaust pulse, thus increasing the velocity of that exhaust pulse. In V6 and V8 engines where there is more than one exhaust bank, "Y-pipes" and "X-pipes" work on the same principle of using the low pressure component of an exhaust pulse to increase the velocity of the next exhaust pulse. Great care must be used when selecting

145-574: A letter–number combination. If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=D800&oldid=1210324989 " Category : Letter–number combination disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages British Rail Class 43 (Warship Class) The British Rail Class 43 diesel-hydraulic locomotives were built by

174-526: A more advanced design, the D800 design drawn up by Swindon Works in turn derived from the original German Krauss-Maffei V200 design . The prime mechanical components of these were two MAN L12V18/21B diesel engines, each rated at 1,100 hp (820 kW) at 1530 rpm and coupled to a Voith LT306r hydraulic transmission; each engine/transmission combination drove one bogie. Unlike the Mekydro four-speed transmissions in

203-439: Is a direct function of the velocity of the high and medium pressure components of the exhaust pulse. Performance headers work to increase the exhaust velocity as much as possible. One technique is tuned-length primary tubes. This technique attempts to time the occurrence of each exhaust pulse, to occur one after the other in succession while still in the exhaust system. The lower pressure tail of an exhaust pulse then serves to create

232-400: Is created in all exhaust systems each time a change in density occurs, such as when exhaust merges into the collector. For clarification, the rarefaction pulse is the technical term for the same process that was described above in the "head, body, tail" description. By tuning the length of the primary tubes, usually by means of resonance tuning, the rarefaction pulse can be timed to coincide with

261-416: Is to insulate a standard or aftermarket manifold. This decreases the amount of heat given off into the engine bay, therefore reducing the intake manifold temperature. There are a few types of thermal insulation but three are particularly common: The goal of performance exhaust headers is mainly to decrease flow resistance ( back pressure ), and to increase the volumetric efficiency of an engine, resulting in

290-494: The North British Locomotive Company (NBL) from 1960 to 1962. They were numbered D833–D865. The D800 series diesel-hydraulic 'Warship Class', of B-B wheel arrangement , was constructed by two different builders. Those locomotives built by British Railways at Swindon Works were originally numbered D800-D832 and D866-D870. They were allocated Class 42 under the 1968 classification system, while those built by

319-644: The North British Locomotive Company (NBL) were originally numbered D833-D865 and allocated Class 43. Because of their early withdrawal dates, neither the Swindon- nor the NBL-built locomotives carried TOPS numbers. More detail on factors common to both types can be found in the article on the Swindon-built British Rail Class 42 . The NBL-built D800s differed mechanically from the Swindon-built batch:

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348-577: The Westerns , Peaks and Brush Type 4 . Even in their last year in service, Class 43 locomotives were still hauling long-distance passenger trains over the summer of 1971 on services between Paddington and locations in Devon. The NBL-built D800s were withdrawn before their Class 42 sisters, themselves doomed to a short life because of the decision to standardise on diesel-electric transmission for mainline locomotives. None have survived into preservation. Many of

377-527: The "Modernisation Plan" was announced. MAN were equally keen to obtain a slice of the UK market for themselves. The first results of this collaboration were the D600-D604 locomotives which failed to take advantage of the weight-saving potential of light alloy stressed-skin construction allied to hydraulic transmissions. No further examples of this design were ordered but NBL then received an order for 33 locomotives to

406-563: The German DB class V 200 design had nickel-resist steel manifolds and were far less troublesome. The engine design also suffered from being quite highly rated for a design with no active piston cooling and piston ring life expectancy was decreased as a result. One MAN L12V18/21B was sent to the British Internal Combustion Engine Research Association for various tests and potential modifications to improve

435-617: The Swindon locomotives used Maybach engines connected to Mekydro hydraulic transmissions whereas the NBL-built examples used MAN engines and Voith transmissions. NBL had entered into an arrangement with the German company MAN AG in the early 1950s to market MAN's engine designs in the UK: NBL was anxious to enter the diesel locomotive market, especially once it became apparent that British Railways would be seeking large quantities of such locomotives when

464-514: The Swindon-built locomotives, the Voith was only a three-speed design but was chosen because it kept compatibility with D600-4 and because NBL already had a licence to manufacture it. Whereas the Swindon-built locomotives had all their engines and transmissions supplied by the German manufacturers (albeit with ten engines and three transmissions supplied as kits of parts for the British licensee to re-assemble)

493-417: The combustion products from the cylinder and induct the intake charge during the overlap period when both intake and exhaust valves are partially open. The effect is known as "scavenging". Length, cross-sectional area, and shaping of the exhaust ports and pipeworks influences the degree of scavenging effect, and the engine speed range over which scavenging occurs. The magnitude of the exhaust scavenging effect

522-546: The deficiencies but nothing ever came of this. Further problems arose due to converting metric to imperial feet and inches when the MAN drawings were received by NBL. It is likely that rounding errors in these conversions resulted in poor tolerances and lowered reliability in practice. Despite all this, figures for 1965 show the North British Warships covered a far greater annual mileage than contemporary Type 4 's such as

551-421: The double pulse was left and what the mixture of that pulse was. Today's understanding of exhaust systems and fluid dynamics has given rise to a number of mechanical improvements. One such improvement can be seen in the exhaust ultimate power valve ("EXUP") fitted to some Yamaha motorcycles. It constantly adjusts the back pressure within the collector of the exhaust system to enhance pressure wave formation as

580-484: The engines and transmissions required for D833-65 were all built by NBL. In operational service, the NBL locomotives were less reliable than their Swindon-built cousins. Mild steel was used for the exhaust manifolds and these components were prone to fracture. Not only did this result in a loss of exhaust pressure to drive the turbochargers but also the driving cabs rapidly filled with exhaust fumes. The MAN-built engines used in

609-465: The exact moment valve overlap occurs. Typically, long primary tubes resonate at a lower engine speed than short primary tubes. Crossplane V8 engines have a left and right bank each containing 4 cylinders. When the engine is running, pistons are firing according to the engine firing order. If a bank has two consecutive piston firings it will create a high pressure area in the exhaust pipe, because two exhaust pulses are moving through it close in time. As

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638-654: The exhaust pipe. For many engines, there are aftermarket tubular exhaust manifolds known as headers in American English , as extractor manifolds in British and Australian English , and simply as "tubular manifolds" in British English . These consist of individual exhaust headpipes for each cylinder, which then usually converge into one tube called a collector . Headers that do not have collectors are called zoomie headers . The most common types of aftermarket headers are made of mild steel or stainless steel tubing for

667-517: The exhaust—the EXUP valve—at the point where the four primary pipes from the cylinders join. This junction point essentially behaves as an artificial atmosphere, hence the alteration of the pressure at this point controls the behavior of reflected waves at this sudden increase in area discontinuity. Closing the valve increases the local pressure, thus inducing the formation of larger amplitude negative reflected expansion waves. This enhances low speed torque up to

696-438: The header(s) are tuned to a particular engine speed range according to the intended application. Typically, wide primary tubes offer the best gains in power and torque at higher engine speeds, while narrow tubes offer the best gains at lower speeds. Many headers are also resonance tuned, to utilize the low-pressure reflected wave rarefaction pulse which can help scavenging the combustion chamber during valve overlap. This pulse

725-433: The length and diameter of the primary tubes. Tubes that are too large will cause the exhaust gas to expand and slow down, decreasing the scavenging effect. Tubes that are too small will create exhaust flow resistance which the engine must work to expel the exhaust gas from the chamber, reducing power and leaving exhaust in the chamber to dilute the incoming intake charge. Since engines produce more exhaust gas at higher speeds,

754-471: The names were later allocated to Class 50 locomotives , which were also named after British warships. They were allocated to Bristol Bath Road , Laira Plymouth , Newton Abbot and Old Oak Common . Built by NBL, date of order 3 July 1958, maker's order no. L100, Swindon lot no. 443 Exhaust manifold Exhaust manifolds are generally simple cast iron or stainless steel units which collect engine exhaust gas from multiple cylinders and deliver it to

783-399: The pressure slightly. Without an X-H pipe the flow of exhaust would be jerky or inconsistent, and the engine would not run at its highest efficiency. The double exhaust pulse would cause part of the next exhaust pulse in that bank to not exit that cylinder completely and cause either a detonation (because of a lean air-fuel ratio (AFR)), or a misfire due to a rich AFR, depending on how much of

812-468: The primary tubes along with flat flanges and possibly a larger diameter collector made of a similar material as the primaries. They may be coated with a ceramic-type finish (sometimes both inside and outside), or painted with a heat-resistant finish, or bare. Chrome plated headers are available but these tend to blue after use. Polished stainless steel will also color (usually a yellow tint), but less than chrome in most cases. Another form of modification used

841-480: The two pulses move in the exhaust pipe they should encounter either an X or H pipe. When they encounter the pipe, part of the pulse diverts into the X-H pipe which lowers the total pressure by a small amount. The reason for this decrease in pressure is that the fluid (liquid, air or gas) will travel along a pipe and when it comes at a crossing the fluid will take the path of least resistance and some will bleed off, thus lowering

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