The car was almost identical to the final development version of the car, the BT52B, but featured larger sidepods for improved cooling, and the turbochargers and intercoolers were repositioned for better fuel efficiency as refuelling stops were now banned, leading to the car having to carry an enlarged (220 litre) fuel tank. The turbocharged BMW M12 engine now produced around in qualifying trim, de-tuned to for the races, making it the most powerful car ever seen in F1 at the time. This power allowed Piquet to record the fastest speed trap of the 1984 season when he clocked on the 1 km long straight at the old Kyalami circuit during qualifying for Round 2 of the championship in South Africa.