One as a big turret, the other doesn't. Toss in a few armor plates and you've got your 10t...
Other also has "big turret" with 30 mm gun (original weights 13,5 t.). Every one with even basic understanding will admit, that almost 10 t. weight difference means a completely new vehicle. It was simple example for those who fail to understand other differences.
Not really. It's (imo very obviously) a modification of the BTR-3 (which itself is the BTR-94 which is just a slight update of a BTR-80) where the front end layout was redesigned to add doors for the driver/commander, the engine was moved to the middle where the turret was, the turret was moved to where the troop compartment was, and the crew compartment was moved to the back where the engine was, and rear doors were added instead of side doors and the roof was heightened a bit at the back in the troop compartment area.
Yeah-yeah, one can call it "modification"... Suspension is also the same, right? What about engine? Gear box? Propulsion on water? Is it the same? Is the hull the same? Is the system of bringing up the front water spoiler the same on BTR-80 and BTR-4? Where are the fuel tanks located?
I think you noted enough differences yourself. Plus my questions pointed to where other significant differences are. My conclusion: BTR-4 is completely new APC, that has nothing to do with BTR-80. Thank you.
It is still technology demonstrator, it is unknown when real prototype or prototypes will be shown, although technology demonstrator as we can see is at least partially functional. It was at least for now, tested in two light tank variants, one with seen here Belgian CT-CV turret armed with 105mm low recoil gun, and one with Polish made turret armed with RUAG 120mm smoothbore CTG gun, and there were also two IFV variants tested, one with manned Hitfist-30P turret, the same used on Rosomak, as we ass with Hitfist-OWS unmanned turret. For now I also only know that firing tests were done with a light tank version with Polish made turret with 120mm gun, dunno if such tests were done with other variants.
Polish Army is from what I know, mostly interested with all variants besides a light tank variant (we need more MBT's than light tanks, however it is possible that also light tank variant in future could be purchased to supplement MBT's), but customer will be able to purchase any variant or variants he wish. So besides replacing or purchasing IFV variant, customer can build up a whole family of vehicles reducing stress on logistics and reducing costs of use of such vehicles.
However as I said, it is still only technology demonstrator, so many, many things can and probably be changed in design, it can even end as a much heavier and better armored vehicle.
Also what should be worth to said, vehicle have preaty interesting powerpack, because besides engine and transmission block, it also contains a device called starter-generator that among several other things, also enables vehicle to move without using engine, only on electric power. It is something similiar to hybrid engine, but not being a hybrid AFAIK.
The engine is 8V199 TE20 made by MTU . It is not specified whether it is a unit with a capacity of 530 kW used to power Boxer or a later version with a capacity over 600 kW used in ASCOD-SV. It have the starter-generator with a capacity of up to 120 kW (also made by MTU). It is placed between the engine and the transmission, it can change energy made by engine into electricity (and vice versa), received power can be stored in batteries or power electrical devices installed in vehicle. What should be noted, the maximum power of the propulsion system should be treated as a total power of the engine and starter-generator. Other ways to use this device is to move vehicle only by using the electric drive without running the engine, which can be especially useful on reconnaissance missions. A similar solution has been applied on ther Piranha V (selected by Great Britain as vehicle, that will be a base for wheeled version of FRES).