Does the engine lose much force with the shield?

Technically the engine does not lose strength with the shield.
The primary role of an armoured vehicle engine is that you must move a greater weight with the same force. Therefore, the result could be that the vehicle can turn more slowly. Depending on the level of armor, a level 3 today is a shield of light representing an approximate weight of 10% of the weight of the vehicle. So we could say that if an armoured vehicle where its extra weight is 10 per cent, it would lose around 10% in acceleration.
Some shielded more heavier than the shield 3D-Shield, we could go up to 20% additional weight equally representing a 20% more than lost in acceleration.