Project Pure Performance E46 Time Attack
In the pages of MotoIQ, we have partnered with Pure Performance in Laguna Hills California for many of our BMW projects. Why? Because Pure Performance, eats sleeps and breaths BMW performance both on the street and through racing with customer cars and their own shop race car.
We will be collaborating with Pure Performance on the building of a RWD limited class car for Superlap Battle. The car of our choice is a E46. We choose the E46 because, well, we have always loved the styling of the car! The fact that the E46 chassis is coming down in price on the used market and Pure Performance just happened to have a straight stripped shell lying around sealed the deal.
In the first stage of the cars construction we will be approaching the building of the backbone of any car, a nice all inclusive roll cage. For any race car the cage is the heart of the chassis. For proper suspension tuning, the chassis must be as rigid as possible. This is for two reasons, the natural frequency of the body structure must be higher than any natural periodic vibration that can be induced into the structure in operation. If the induced vibration is the same as the natural frequency or a low order harmonic of it, the vibration can build and become a force that can cause tire shock. The body of the car is a huge undamped spring that if allowed to flex freely, can add uncontrolled energy into the suspension itself causing tire shock and loss of potential grip.
The other reason for a good cage is to protect the meat sack behind the wheel in the event of a crash. A good cage can keep the drivers compartment intact in a severe crash, yet have some controlled compliance to help spread out the force impulse to protect the driver. A good cage should also be able to absorb multiple impacts and rolls.
Take a look and see how our cage came out as our car progresses from a bare shell to a hopefully competitive Time Attack Machine.