VM Motori 'Turbo D'
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- Last Updated on Thursday, 20 October 2011 18:32
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A diesel engine for the Range Rover. At Land Rover this had been thought about for a while, but money was not available to carry out the necessary engineering involved. Thus it was not until 1986 that the Range Rover gained a diesel option in the shape of the VM Motori engine, dubbed the 'Turbo D' for Range Rover. The VM engine had previously been used successfully in the Rover SD1 (SDTurbo model) from 1982 to 1985.
VM Motori was (and is) a well established Italian engineering company, founded in 1947 by Vancini and Martelli (VM) and is specialised in air and water cooled diesel engines.
The Range Rover 'Turbo D' provided the best package available at the time of power and refinement in a turbo-diesel engine, and continued to be fitted throughout the Land Rover Defender 2.5 'Diesel Turbo' (19J) years until the fitment of the 200tdi engine in the Range Rover in 1992.
The 2400cc VM engine is now generally seen as the most modern diesel engine of its time. In the Rover SD1, it was a real alternative for a petrol engined car. Giving 90hp and a top speed of 102 mph (165 km/h) it was the fastest diesel of its time and it could drive a kilometre from a standing start in 37.7 seconds. Power was uprated for the Range Rover version.
The engines were manufactured in the VM factory in Cento, Ferrara Italy. It's engine code is 'HR 492 HT'. The abbreviation stands for the following:
HR means High Revolution, 4 cylinder, a 92 mm bore, H stands for water cooling and the T for the turbo.
VM started work on the HR engine series just after the 1973 oil crisis with the goal of finding a modern answer to reducing fuel consumption. Production of the engine began in 1978.
When designing the HR engine, VM had set very ambitious goals:
A diesel of the newest generation, which was designed for use with a turbo from the outset.
A very robust design that was built according to industrial stationery engine production tolerances, cutting edge design solutions which should lower the traditional engine weight close to that of a petrol engine and patented innovations decreasing engine vibration and helping to silence the usual diesel knock sound.
The complete HR series consists of 3, 4, 5 and 6 cylinder engines, each in two capacity versions of either 500 or 600 cc per cylinder. In total the series consists of 8 engines with indirect injection using a Ricardo Comet V pre-combustion chamber. The 2400 engine used in the Range Rover was a four cylinder with 600 cc per cylinder, making a total capacity of 2393 cc. The later (2500) version of the engine employed direct fuel injection and a longer stroke which provided a displacement of 2,499cc.
The common denominator or the HR engines is their modular structure. All engines have been designed as multiples of each other. The inlet and outlet manifolds are both located at the same side of the head. This made it easier to place a turbo on the engine.
Two further important characteristics of the HR engine are the tunnel shaped block and the separated cylinder heads. The block is built entirely from cast iron, in which a tunnel for the crankshaft is left open. The usual main bearing caps that support the crankshaft are integrated in the engine block. In the direction of the sump the engine has five barriers in between each cylinder. Through these barriers runs one single tunnel in which the crankshaft is built in. The crankshaft in its turn is supported by five strong aluminium main bearings. These bearings are not connected to the tunnel. With the engine running, the expansion of the aluminium being three times greater than that of steel presses the bearing tightly to the block. The thick layer of aluminium between the crankshaft and the iron block is a perfect 'sandwich panel' to reduce engine vibrations and noise.
The cylinder heads are made of aluminium and are fully separated for each cylinder. They are absolutely identical and interchangeable pieces, with each cylinder head bolted onto the main block with six bolts. The chances of getting a warped cylinder head are small with this setup. This makes them harder to produce but is a key factor in making a strong reliable engine. It should be noted that during the heating up process the difference in expansion between a single cylinder head and the head of the cylinder block exceeds 1 millimetre.
Engine Code: HR 492 HT / VM81A / VM 4 HT 2.4 / HR 492 OHV
Layout: 4-cylinder, inline
Block/Head: Alloy/Iron
Valves: OHV, gear driven, push-rod operated
Capacity: 2,393 cc (146.0 cu. in)
Bore x stroke: 92.0 mm x 90.0 mm (3.62 in x 3.54 in)
Compression Ratio: 21.5:1
Fuel Injection: Bosch VE 4/10
Induction: KKK 16 turbocharger
Power: 105 bhp (78 kW) 4,200 rpm
Torque: 176 lbf·ft (238 N·m) @ 2,400 rpm
Production: 1978-?
Used in: Rover SD1 (1982-1985), Range Rover (1986-1989), Alfa Romeo 75, 90, Alfetta
Engine Code: HR 492 / 425 OHV
Layout: 4-cylinder, inline
Block/Head: Alloy/Iron
Valves: OHV, gear driven, push-rod operated
Capacity: 2,499 cc (152.5 cu. in)
Bore x stroke: 92.0 mm x 94.0 mm (3.62 in x 3.70 in)
Compression Ratio: Unknown
Fuel Injection: Unknown
Induction: KKK Turbocharger
Power: 119 bhp (89 kW) 4,200 rpm
Torque: 209 lbf·ft (284 N·m) @ 1,950 rpm
Production: 1978-?
Used in: Rover 800 (1990-1997), Range Rover (1989-1992), Alfa Romeo 155, 164, Jeep Cherokee, Dodge Dakota
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