[mwebb]

since we know that
what ever EGR percentage is on an OEM system does yield improved FE over 0 percent EGR

it is not a far stretch to deduce that INCREASING EGR flow percentage up to the point where misfire is induced OR efficiency is reduced
should also improve FE

testing
in the real world on a real car with real test equipment would be needed to see
how much EGR flow could be increased , it would have to be regulated and increased a wee little bit at a time
changing exhaust back pressure will screw up the EGR modulator 's ability to control EGR flow ....
another failed experiment

i have inadvertently increased EGR percentage by changing cam timing on a G10
the exhaust valve closed before all the spent combustion gases could be expelled
FE was not improved and drivability was reduced
DO not use the 3tech +10 cam wheel with the 3tech economy cam or you will repeat my inadvertent experiment


the 3tech economy cam by itself is an improvement with the OEM cam wheel
.............................
just because 2 experiments failed does not mean that it can not be done
a bit more testing is needed .... and time always has a way of flying away before the testing can be done

Originally Posted by drbobwoolery

responding to:

while interesting to ponder , there is no reason to use engine braking for this condition
============================
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.