hey guys i rebuild diesel engines and i am a facing a very serious problem as i am required to increase a diesel engine hp by at least 20% without adding a turbo charger i tried changing the fuel pump but it only increase 5% which is not enough do you have any idea what i should do ???? right now we are thinking about increasing the piston diameter , do you think this will work??? the engine i am rebuilding is a 5 cylinders produced by deutz germany, and it should be 160hp and max rpm is 2500 r/m the problem is it achieved the maximum power which is 150hp at 1700 r/m and what is required is to achieve the maximum hp at the maximum speed which is 150 hp at 2500 rpm ps. it is a fully mechanical engine no electronics involved in it any ideas ??????????