wo aug 23, 2006 20:44
VM Motori is a well established Italian firm founded in 1947 by Vancini and Martelli (VM) and is specialised in air and water cooled diesel engines. Since 1995 it is a part of the Detroit Diesel company.
VM started work on the HR engine series just after the Kippur-crisis with the objection to find a modern answer to energy problems. Lots of investigations and attempts were carried out in this time, both for petrol engines as for diesel ones, all with the same goal of reducing fuel consumption.
The HR engine was in fact the first where this modern technology was put to use.
Other achievements have been acquired against nature's natural drawbacks of the heavy sturdy diesel.
In some cases a clever but simple conversion of a petrol engine was realised but much more was attempted to improve diesel performance by applying turbo compressors.
With 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 initial design.
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 silencing the dreadful diesel sound.
The 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-chamber.
The diesel engine we are talking about here came into life in 1978 and is produced until this day, however much has been improved during the years off course. The engine was built in three, four, five and six cylinder configurations for various companies like Alfa Romeo, Ford, Jeep, Toyota , Chrysler and
Rover.
The concept might be a bit old fashioned at first, no overhead camshaft but a pushrod engine with the camshaft located low in the cylinder block. However as a diesel doesn't like to be revved not having an overhead cam is not an important point. It makes it possible to drive the camshaft, waterpump, and oilpump directly from the crankshaft by gears instead of using a chain or belt drive.
The cylinderhead is different from any engine on the market. Where a normal engine has one head for all the cylinders, or two in case of a V or boxer construction, this in-line engine has a separate cylinder head for every cylinder. This unusual setup has been chosen because it allows one cylinder head casting to be used for all engine configurations, be it a three or a six cylinder. Every cylinder head is bolted onto the main block with six bolts. The chances of getting a warped cylinder head are very small with this setup.
The combustion chamber was based on a design by the British Ricardo firm, one of the leading engine designers in the world. The chamber design, called Ricardo Comet V, was optimised for maximum swirl effect. A further strange thing about the head design, the inlet and outlet manifolds are both located at the same side of the head. This sure makes it easier to place a turbo on the engine.
And if the cylinder head isn't strange enough, how about a diesel engine with a tunnel carter... Normally an engine has main bearing caps which are bolted to the cylinder block. Not so with the VM diesel. A Tunnel carter looks more like the picture below, it's from an old Ferguson engine but it shows the tunnel carter setup very good.
The entire crankshaft can also not be installed from underneath but has to be put into the engine through the tunnel. However this construction makes the engine very very stiff and the crankshaft is fitted without any stress by main bearing caps. A very nice and elegant solution only found in exotic race engines.
The VM diesel was equipped with a KKK turbo charger, The engine was designed right from the beginning for use with a turbo.
Despite the turbo, power isn't really impressive the 2.4 litre delivering 90 bhp at a lowly 4,200 rpm. Nowadays you can expect around 136 bhp at 4,400 rpm from the Range Rover 2.5dt Turbo diesel engines.
The greatest problems with this engine were deformation of the cylinder heads and their seals.
To attach the heads to the block the way of greatest freedom was chosen: every single cylinder head can expand in every direction, without raising pressure on the cylinder block and expand separately from the other cylinder heads.
The result being a diesel engine that will pass any heat/stress test without problems. It should be noted here that during heating up the difference in expansion between a single cylinder head and the head of the cylinder block exceeds 1 millimetre!
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.Tja raar verhaal, ik denk gewoon dat hij beter naar een andere garage kan gaan.
