List of GM engines: Encyclopedia II - List of GM engines - Diesel

List of GM engines - Diesel

The history of Diesel engines at General Motors has not been positive. In the 1970s, the company was unable to power its large cars and trucks with their emissions-strangled engines. Like many other companies, GM turned to Diesel power, directing the Oldsmobile division to develop two V6 and one V8 to be shared with all divisions.

Oldsmobile's engines, the 5.7 L LF9 and 4.3 L LF7 V8s and 4.3 L LT6/LT7/LS2 V6, were notoriously unreliable. Although over one million were sold between 1978 and 1985, the failure rate of GM's engines ruined the reputation of Diesel engines in general in the United States market. Eventually, a class action lawsuit resulted in an arbitration system under the supervision of the Federal Trade Commission where consumers could claim 80% of the original cost of the engine in the event of a failure.

The Oldsmobile Diesel’s Problems

Despite the fact that these engines looked in large part like their gasoline cousins, they were indeed quite different. The castings were much thicker and heavier, and a higher quality alloy was used for the block and heads. The main and rod bearing journals were also increased in size to compensate for the higher operating stresses and pressures that diesels exert on their reciprocating parts. The primary problem with GM's Diesel engines of the 1970s was due in large part to poor fuel quality (diesel fuel was notoriously filthy and contaminated with water in the late 1970's), which caused corrosion in the fuel injection pump. This corrosion could (and often did) cause an incorrect injection cycle, which would produce abnormally high cylinder pressures. This in turn would cause the cylinder head to "lift" up off of the block, and stretch (or even break) the head bolts. Once the head gasket was compromised, the gasket would leak coolant into the cylinder. At 22.5:1 compression, there was little volume left in the cylinder at TDC. The uncompressible quality of liquids means that the engine would hydro lock, breaking pistons, crankshafts, connecting rods, and other parts, resulting in complete and catastrophic engine damage. Why then, did other Diesel engines, from GM and other companies, not have these problems? The answer lies in the lack of an effective water separating system, such as can be found on other diesel applications. Overall, the main ingredients of disaster that affected this engine lie in: 1) A poorly designed fuel system, which was fostered by a desire to insulate the consumer from the unpleasant aspects of Diesel ownership. 2) A misguided attempt to market the diesel engine as if it was as convenient to operate and maintain as a gasoline engine. 3) A poorly trained service staff which often used the incorrect oils and service procedures for this (and any, for that matter) Diesel engine. These factors combined to create the ultimate downfall of this engine. In the hands of an experienced diesel operator, these engines can (and often do) travel for hundreds of thousands of trouble free miles. However, for a society of people who just "gas and go", this engine was particularly ill suited to the task.

In the 1980 and 1990s GM produced the 6.2 liter and 6.5 liter V8 Diesels for use in light trucks and in the HMMWV.

Today, GM uses Diesel engines from DMAX (for trucks) but offers no domestic Diesel passenger cars. General Motors' Opel division is one of the leading proponents of Diesel cars in Europe, however. Opel uses common rail direct injection engines designed and produced by Fiat S.p.A and Isuzu. Ownership of both designs was acquired by GM in 2005, and a new GM Powertrain division in Turin, Italy (home of Fiat) was founded to manage these assets. GM Daewoo recently licensed two common rail designs from VM Motori.

Adapted from the Wikipedia article "Diesel", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki