If you go study the rationale behind the development of the Leopard series you'll understand that high power to weight ratio is fundamental for every MBT.
I suggest that you get a calculator and check your figures... an Abrams is 72 tons in battle configuration and with its 1,500hp engine comes in at 20.8 hp/ton. The T-90AM with its 1,150hp engine and 48 ton combat weight comes in at 23.95hp/ton... so what is the problem? The Challenger II at 63 tons and a 1,200hp engine comes in at 19.04hp/t.
...is it worth even doing the calculation for the Merkava?
I mentioned the BMD because of its 35hp/t power to weight ratio... which certainly didn't make it better than other IFVS.
Well, not rubbish because I'm talking about the V-96 12 stroke Diesel.... Btw: the thing about a turbine is that you can fuel it with whatever, that's what it's a turbine for!
Russian T series tanks of the T-72 and T-90 series use multifuel diesels. The V-96 can use diesel, petrol, kerosene, benzine or their mixtures. Part of the advantage of a digital fuel control system...
The main problem with gas turbines is lack of low speed torque. The stopping and starting and acceleration is the worst way to use a gas turbine engine because it needs to be operating at high revs to generate the torque to accelerate.
Optimally a gas turbine will have an efficient RPM at which it will out perform a diesel engine in fuel efficiency, and will be much smaller and more compact than a diesel engine of similar power. That is why APUs are almost always gas turbines on tanks and aircraft... connect them to an electric motor and run them at efficient speed and you have an efficient power supply. Try to move a 50-70 ton vehicle around rough country and you have a fuel vacuum that will cost more in fuel than any other part of the tank.
And that is the fact that it still is underpowered and underarmered. Russia has a 1250hp engine. Why not install that?
Because it is a custom designed engine, designed for Armata, which can take a larger engine.
The X shaped diesel engine for the Armata is going to start at about 1,400hp, but has potential to operate at 2,400hp at the expense of engine life. Through the life of the engine with improved design and new materials the engine power will increase and engine life will increase too. At the moment it is very new.
The T-80U is in the same boat and as it has a gas turbine engine that guzzles fuel it would be much more cost effective to replace that with pretty much any engine. The problem of course is that the Gas Turbine engine fitted is tiny so no diesel engine currently available will fit, so they wont just scrap them because they are still good tanks, so they will use them till they are worn out and then discard them.
I mentioned. I'm just seriously worried about it's survivability.
Its problems with survivability are not centred around armour protection... but ammo storage.
in real combat against modern anti tank weapons used by professionals that have served in the Soviet Military the T-72 fared better than the T-80 when it went into combat without the extra ammo in the crew compartment.
In urban warfare the threat can come from anywhere and a sensible enemy will attack from the rear and the top.
Perhaps instead of looking at Leopards in NATO training you should look at the combat record of the T-72s in Chechnia or Georgia/South Ossetia.
But it still lacks mobility in comparison. Leopard runs at 72 kilometers per hour. T-90AM cannot match that unless you install a more powerful engine.
No tank in the world travels at 72km/h except on very flat good quality straight roads, and in combat a tank travelling at that speed will quickly leave their support vehicles and logistics tail behind and end up on their own.
Shturm and Ataka can easily hit targets travelling much faster than 72km/h... they can also hit low flying aircraft.
I would suggest that top speed is the least important factor for a tank, it is acceleration at low speeds from standing starts... moving from cover to cover. the less time the vehicle is exposed to the enemy the safer it will be to all manner of missiles and cannon fired rounds.
The real problem with more powerful engines is that even if they are more fuel efficient that doesn't mean the burn less fuel.
Compare the V-84MS engine of the T-72S with the V-92S2 engine of the T-90S.
The V-84 generates 618kW (840hp) and its fuel consumption is 247 g/kW.h. In other words it burns 247 grammes of fuel per kW per hour it runs. This means at full power (618kW) it burns 247 x 618 = 152646 grammes of fuel... or 152.6 kgs of fuel.
The V-92 generates 735kW (1,000hp) and its fuel consumption is 212 g/kW.h. In other words it burns 212 grammes of fuel per kW per hour it runs. This means at full power (735kW) it burns 212 x 735 = 155820 grammes of fuel... or 155.8kgs of fuel. It generates more power, but it also burns more fuel.
The V-46-6 of the T-72A is a 574kW (780hp) engine and its fuel consumption is 245 g/kW.h. This means at full power it burns 245 x 574 = 140.6kgs of fuel, which is clearly the most "efficient" in terms of logistics, but is also the least powerful.
As mentioned on another thread somewhere by Runaway... where he is the T-72 operates, but the Leopard can't operate on the terrain. In deep snow, bog, deep mud, and lots of other terrain types a lighter tank will pass and a heavier tank will sink.
Before desert storm there were actually fears that the Abrams might sink in certain sand conditions...