mode was selected at 504 and the maximum number of times emergency by pass mode may be entered has not been exceeded at 511 as determined by referencing a counter then at 512 a first timer t 1 may be set for using normal engine calibration without reductant dosing if t 1 expires a second timer may be set t 2 at 514 for conservation engine calibration without reductant if t 2 expires the system goes to 520 which is the engine calibration for low engine out emissions and no reductant dosing 522 it may be appreciated that during either t 1 or t 2 there may be relatively high tailpipe emissions as shown at 518 in such a manner i e operating the engine under low engine out emission calibration at 520 the engine may then reduce tailpipe emissions such that relatively low tailpipe emissions may be produced at 524 such engine calibrations may include as noted above retarded injection timing i e a delay in the start of fuel injection to reduce combustion temperature low pressure loop exhaust gas recycling egr and or high pressure loop egr which may lower maximum combustion temperature lower compression ratios lower temperature combustion and or premixed controlled combustion it may also include control of fuel mass boost pressure air flow amount and temperature variable valve actuation timing and lift and control of the amount and temperature of recycled exhaust gas if reductant low engine control mode is not selected at 506 then a determination may be made as to whether reductant dosing conservation engine control mode has been selected at 508 such selection.