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Compression is a key design attribute of both compressible seals and coupled hose systems. Traditional design techniques use 3-sigma upper and lower limits from capability studies on critical component dimensions to estimate potential compression variation. Probability calculations are shown that indicate that the true variation in compression is much less than this estimate. An alternative approach using probabilistic design techniques to calculate true 6-sigma (+/-3-sigma) compression variation is shown for both a typical radial seal and a hose coupling. The results are then compared to Monte Carlo simulations using representative data sets for each critical dimension.

The pressure variation in the fuel supply system due to injector firing and other system inputs has been widely discussed in SI engine technology. It can affect engine calibration, performance and compliance to emission standards through its effect on fuel distribution between the cylinders. It can also generate mechanical noise and vibration that may be annoying to the occupants of the vehicle. Much discussion has focused both on modeling this condition and on ways to alleviate the problem through the use of damping devices. This study presents topographical maps of fuel pressure variation over the engine operation range for a simple non-damped rail with a variety of injectors. The injectors tested are manufactured by different companies and have different flow rates.