Challenger 2 (Auxiliary Power Unit - APU)

I’m here to talk a missing feature from the Challenger 2 platform.
The APU.

What is an APU? Why is it important?

An APU (Auxiliary Power Unit) is in essential terms, a smaller engine mounted along side a larger one that produces electrical power. This allows the vehicle to have the main engine turned off, reducing its heat signature, and sound profile, while maintaining the ability to keep batteries charged, and all electronic devices inside the vehicle working, i.e. internal lighting, heating, cooling, screens, battlefield tracking, radios, powered traverse, thermals, rangefinder, tea making facilities, by using the power from the smaller engine. think of it as a low power mode, standby mode, or stealth mode or charging mode, allowing crews to “lay low” and keep a reduced signature, for either defensive movements or ambush positions. These engines do not have the power to move the vehicle and would only be useful while the vehicle is stationary with the main engine turned off as the main engine will do this smaller ones job while it is running. The APU (smaller engine) is used for when stealth/laying low is required. It is to note, this does not completely silence the vehicle, but it does lower the volume of the vehicle significantly, due to the size of the APU in comparison to the main, larger engine.

What APU does the Challenger 2 use?

The challenger 2 features an Extel Systems Wedel Auxiliary Power Unit (APU), it is based on the Perkins P404C-22 diesel engine. Older versions of the challenger 2 had a Perkins P4.108 (left) which was later replaced to the P404C-22 (right). fig.1

perkins engines
Engine Statistics:
Perkins P4.108 (older) produces 33.9kw at 3600rpm with 46hp
Perkins P404C-22 (newer) produces 38kw at 1800rpm with 51hp

Final Notes

With the Challenger 2 being essentially a hull down vehicle, keeping your thermal signature and sound profile to a minimum is important to a defensive vehicle, hence why Barracuda thermal blankets have been seen equip on many challenger 2’s over the years, in an attempt to make their hulled down positions better hidden from enemy forces; this would play especially true in war thunder due to the challenger 2 having low mobility and hull armour, meaning that it relies on its hull down capability more to be effective, therefore its playstyle lays within that, hulling down, defending positions and keeping a low profile from a distance.

I am aware that there are other vehicles out there that require their APU units the same as the challenger 2 (such as the Leopard 2), but for this vehicle it plays directly into the vehicles playstyle and would help it be more competitive without being completely game changing in my opinion.

So on that I leave it to the community! I would love to hear people’s opinions on this, and I hope the format of my post was not too unbearable. Thank you for reading!

(I’d love to see the reason to votes below if you have the time!)

Do you think giving tanks their APU units would fundamentally break the game?
  • Yes
  • No
0 voters


Should the Challenger 2 (or all tanks that have them) recieve its APU?
  • Yes
  • No
0 voters

It could be nice that every tank in game got its APU (if there is one). The M1 Abrams (SEPv3), some Leopard variant, newest Leclerc … got one (to my knowledge but I may be wrong).


It would be nice for tanks like challenger chieftain and so on to have their donkey engines but having your power go out when you lose engine is good for balance, your tank is disabled so should be so.

they are modelled on some tanks just as part of the engine too, they just don’t work

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forgot the term “donkey engine” was a thing! but yes! hope more vehicles get their “donkey engines” now that Gaijin are adding more modules.

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would be great to see

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