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responding to:
while interesting to ponder , there is no reason to use engine braking for this condition
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EGR does improve FE ...
where are you going with your comments on EGR ?
Claims of increased efficiency with max EGR short of misfire are mostly based on reduction of pumping losses, restriction across the throttle plate, etc.
If there is much to be gained with the cam, compression ratio, exhaust system by reducing pumping losses, this should be evident in downhill coasting in gear with the fuel off, comparing the OEM throttle closed drag with the drag associated with WOT. If it is difficult to decide about the effect in this situation, the pumping losses are small enough to not be worth trying to reduce with EGR.
OTOH, if opening the throttle feels like letting off the brake, in gear, no fuel, then there IS something to be gained.
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