Engines for Armor: AVDS-1790

The AVDS-1790 is the descendant of the 1950s vintage AV-1790, from the days when American armored vehicles still used gasoline engines. It was redesigned to use diesel (the “D” in the initials) and use a supercharger (the “S” in AVDS) for more power. The supercharger has been replaced by a twin-turbocharger setup, and the engine has been refitted with modern, computer-controlled, common-rail fuel injection. Continental Motors, now a division of L-3, currently offers the AVDS-1790 in 750, 950, 1,050, 1,200, and 1,500 horsepower versions. The Israelis are big fans of the AVDS-1790, using it on most versions of the Merkava and on the Namer, as well as on their M48 and M60 tanks.

Note that the -1790 in the model number refers to the displacement of cubic inches1, not the horsepower or the torque.

At first glance, the AVDS is somewhat odd. It’s a rather big V-12 diesel. Yawn. It’s notably bigger than the other diesels you will find. But there’s a reason for that: the AVDS-1790 is air-cooled.

Air cooling provides some noteworthy advantages and disadvantages. The engine must be physically bulkier, because air cooling must be attached to the cylinders directly. You can’t pipe heat to a separate radiator. Liquid cooled engines will also see a higher amount of power for a given displacement. Liquid cooled engines are also easier to meet emissions targets with.

On the other hand, air cooled engines are lighter overall. They are significantly simpler, because there are no pumps. Further, and this is important for combat vehicle designers, they are more robust. Damage to cooling for one cylinder will not affect cooling from the other cylinders. The nature of an air-cooled system means it’s a lot easier to maintain, since the fins on the cylinders don’t need much in the way of maintenance.

The maintenance and ruggedness are what endear these engines to the Israelis. I’d be interested to learn more about the intake system on the Merkava, since this is a front-engined tank without the usual large amount of grillwork on the engine bay, and yet the air-cooled engines still work well.

I think most telling for the quality of the design is that having gone to the MTU883 in the Merkava IV, because a 1,500 hp version of the AVDS wasn’t designed yet, the IDF went back to the AVDS-1790 for the Namer.

  1. As is right and proper. Suck it, metric system. 

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