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It is well known that an unplanned component mass increase during vehicle design creates a ripple effect of changes throughout the vehicle subsystems, which require resizing for the additional mass. This in turn, increases overall vehicle mass. And the opposite is true in vehicle mass reduction where subsystem resizing is necessary to account for an initial mass reduction enabled, for example, by a new technology. These secondary mass changes can be significant and must be considered in the mass budgeting process due to their importance to fuel consumption and greenhouse gas emission assessments. Secondary mass reduction may be modeled using subsystem mass influence coefficients-the incremental change in subsystem mass for a unit change in gross vehicle mass. This paper focuses on means to estimate influence coefficients using two methods: Analytical and Regression.

In this paper the mass reduction potentials of steel and aluminum in automotive applications are compared. In order to determine the mass reduction potential of each material, several applications and concepts are analyzed. This is done by evaluation of the mass and the performance of these components. The results are computed based on theoretical mechanical fundamentals and vehicle requirements. The analysis of a series of body structures indicates that aluminum may achieve 11 % to 34 % mass reduction depending on whether it is compared to recent optimized steel designs or to former (non-optimized) steel designs. A hood benchmarking [3] study pointed out, that the substitution of steel by aluminum allows a mass reduction of approximately 36 %. This mass reduction goes along with a material cost increase. Aluminum is primarily used to decrease the mass. But, on the other hand, it is also possible to design steel bumpers that are up to 8 % lighter than a corresponding aluminum bumper.

In this paper the relationship between weight reduction and fuel economy is determined. This is executed with simulations for the three different propulsion systems ICE (internal combustion engine), hybrid system and fuel cell (FC) system. Furthermore, the three different vehicles classes compact, mid-size and SUV are considered along with two driving cycles, NEDC and HYZEM. The re-sizing of the propulsion systems according to the lighter vehicle weight to achieve the same acceleration as the basis vehicle is implemented as well. As an overall result it is established that no general value for the fuel consumption reduction per weight reduction exists. It is very important to consider all boundary conditions, especially the used driving cycle, the examined vehicle class, the type of propulsion system and a possible powertrain re-sizing. In detail the results show values between 2 and 8 % fuel consumption reduction at a 10 % weight reduction.