Talk of the Meredith effect and the P51 in a thread about thrust augmenters/reheat/afterburners, reminded me of an old Farnborough report that would combine the threads together.
This is the summary from the report that was published in November 1943.
"Estimates of the effect of burning fuel in the radiator duct of Mustang behindthe matrix, show that a top speed increase of 45 mph, at all heights ispossible with a combustion temperature of l000°C. Larger increases are possiblewith increased combustion temperatures. Loss of speed with the burners not in actionshould be negligible, and operation for 5 minutes at 1000°C uses sufficientfuel to reduce the subsequent endurance by about 18 minutes."