THE FASTEST LEGO PW CAR! 11,8 km/u! i made a lego power functions car with 1 xl motor and 1 medium motor and it hits 11,8 km/u! is it the fastest lego pw car with one xl motor for driving? post it in the comments below! it has a perfect handling with a new steering mechanism!! I challenge you to make a faster lego car with 1 xl motor. It has a gear ratio of 1:3. it is the best ratio for good speed and ACCELERATION and the last one is what most people forget! but is as important as speed and handling! it even does a hillclimb!