Increasing Engine Power – If I install a kit to increase the engine power, what effect will that have on the transmission?
A. The transmission controls have been highly integrated with the LB7 and LLY Duramax diesels and L18 gas engines in GM pickups. Part of this integration is that the TCM has a ‘map’ of each engine’s torque output throughout its operating RPM. The TCM uses ‘Shift Energy Management’ (SEM). During most range shifts, there is more power available than necessary to maintain acceleration. The unused engine power traditionally goes into slipping clutches, and results in additional heat without adding to vehicle performance. Through engine/transmission communication, SEM is the electronic control process that reduces torque during range upshifts to a level resulting in consistent transmission output torque before and after the shift. The net result is optimized shift quality as well as reduced clutch energy. Needless to say, when engine torque is increased significantly via various after-market methods, these features are greatly compromised. As with any mechanical system, there is a limit to
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