Diesel Engine Troubleshooting

Uniflow Scavenge Opposed Piston Diesel Engines

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In engines of this type admission of air is effected by ‘air piston’ controlled inlet ports, and rejection of products of combustion by ‘exhaust piston’ controlled exhaust ports. The motion of the two sets of pistons is controlled by either two crankshafts connected through gearing, or by a single crankshaft with the ‘top’ bank of pistons transmitting their motion to the single crankshaft through a crosshead-siderod mechanism. By suitable offsetting of the cranks controlling the air and exhaust pistons asymmetrical timing can be achieved.

It is evident that this system displays the same favourable characteristics as the exhaust valve in head system, but at the expense of even greater mechanical complications. Its outstanding advantage is the high specific output per cylinder associated with two pistons. However, the system is now retained only in large low speed marine, and smaller medium speed stationary and marine engines. In high speed form it is still employed for naval purposes such as in some fast patrol vessels and mine searchers, although its use in road vehicles and locomotives is discontinued.

Written by Ed

October 18th, 2011 at 3:12 am

Uniflow Scavenge Single Piston Diesel Engines

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In engines of this type admission of air to the cylinder is usually effected by piston controlled ports while the products of combustion are exhausted through a camshaft operated exhaust valve. Such systems are preferable from the standpoint of scavenging in that the ‘uniflow’ motion of the air from the inlet ports upwards through the cylinder tends to lead to physical displacement of, rather than mixing with, the products of combustion thus giving improved charge purity at the end of the scavenging process. At the same time it is now possible to adopt asymmetrical timing of the exhaust and inlet processes relative to bottom dead centre (BDC) so that, with exhaust closure preceding inlet closure the danger of escape of fresh charge into the exhaust manifold present in the loop scavenge system is completely eliminated. This system has been adopted in a number of stationary and marine two-stroke engines.

Written by Ed

October 18th, 2011 at 3:10 am

Loop Scavenged Diesel Engines

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This is the simplest type of two-stroke engine in which both inlet and exhaust are controlled by ports in conjunction with a single piston. Inevitably this arrangement results in symmetrical timing which from the standpoint of scavenging is not ideal. In the first instance the ‘loop’ air motion in the cylinder is apt to produce a high degree of mixing of the incoming air with the products of combustion, instead of physical displacement through the exhaust ports. As a result the degree of charge purity (i.e. the proportion of trapped air) at the end of the scavenging process tends to be low.

A second adverse feature resulting from symmetrical timing is loss of trapped charge between inlet and exhaust port closure and susceptibility to further pollution of the trapped charge with exhaust gas returned to the cylinder by exhaust manifold pressure wave effects. The great advantage of the system is its outstanding simplicity.

Two Stroke Diesel Engines1 Loop Scavenged Diesel Engines

Two-stroke engines: (a) Loop scavenged engine; (b) Exhaust valve-in-head engine; (c) Opposed piston engine

Written by Ed

October 18th, 2011 at 3:09 am

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Two Stroke Diesel Engines

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In two-stroke engines combustion occurs in the region of top dead centre (TDC) of every revolution. Consequently gas exchange also has to be effected once per revolution in the region of bottom dead centre (BCD) and with minimum loss of expansion work of the cylinder gases following combustion.

This implies that escape of gas from the cylinder to exhaust and charging with fresh air from the inlet manifold must occur under the most favourable possible flow conditions over the shortest possible period. In practice the gas exhange or SC AVENGING process in two-stroke engines occupies between 100° and 150° of crank angle (CA) disposed approximately symmetrically about BDC.

Two-stroke engines may be subdivided according to the particular scavenging system used into the following sub-groups.

Two Stroke Diesel Engines Two Stroke Diesel Engines

Two-stroke engines: (a) Loop scavenged engine; (b) Exhaust valve-in-head engine; (c) Opposed piston engine

Written by Ed

October 18th, 2011 at 3:05 am

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Ford F Front Cover Cooling System Flow

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Coolant is drawn into the inlet of the front cover and then flows from the water pump through the front cover to the crankcase.

Coolant is also routed from the front cover into the crankcase to a passage that feeds the oil cooler.

Return coolant is directed to the thermostat by the front cover. If the thermostat is open, coolant flows to the radiator to be cooled. If the thermostat is closed, coolant is returned to the water pump via a bypass circuit in the front cover.

Written by Ed

October 14th, 2011 at 2:48 am

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Ford F Cooling System Flow Diagram

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Ford F Cooling System Flow Diagram

Written by Ed

October 14th, 2011 at 2:45 am

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Ford F Normal Heat Treatment Discoloration

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The bearing surfaces on the crankshaft are induction hardened.

During the hardening process the surrounding areas of the crankshaft discolor.

This condition is normal.

Written by Ed

October 14th, 2011 at 2:43 am

Posted in F Series

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Ford F Single Mass Flywheel

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A single mass flywheel is used on the F-450/550 Superduty trucks.

The single mass flywheel can be identified by the absence of the above mentioned parts and that it is machined from one solid part.

Written by Ed

October 14th, 2011 at 2:28 am

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Ford F Dual Mass Flywheel

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The 6.0L Power Stroke uses two different flywheels for the manual transmission.

A dual-mass flywheel is used on the F-250/350 Superduty truck.

The dual-mass flywheel can be identified by springs located around the flywheel on the engine side.

It can also be identified by an extra ring of bolts on the transmission side of the flywheel that holds the two masses together.

From the side it can be identified by the separation between the clutch surface and the starter ring.

Written by Ed

October 3rd, 2011 at 4:55 am

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Ford F Rear Geartrain

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The geartrain for the crankshaft, camshaft, and high pressure pump are located in the rear of the engine under the rear cover.

This allows the high pressure pump to be mounted inside the engine and also reduces geartrain noise.

Written by Ed

October 3rd, 2011 at 4:42 am

Posted in F Series

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