Oh This is Karl Schultze-- another of the engineers-- ANOTHER EXPERT--

""..]In this way I, together with Prüfer, also constructed and built the crematoria in Auschwitz concentration camp in 1942/43. I myself only built the part of the crematorium that belonged to the ventilation.
In this camp four crematoria were built during the mentioned period. In two of the crematoria there were five ovens each, and in each of these ovens three corpses were introduced, i.e. there were three openings (muffles) in one oven. Within one hour fifteen corpses could be burned in one crematorium with five ovens.
Question: In what respects did the construction of the crematoria installed in the concentration camps differ from the common crematoria installed by the company in various countries until 1933?
Answer: In the common crematoria there was only one huge opening (muffle), into which a coffin with one corpse could be introduced without difficulty. In the crematoria of the concentration camps the ovens had not one but three openings, and there were five ovens in one crematorium.
Thus in one concentration camp crematorium there were fifteen openings (muffles), instead of one like in a common crematorium.
In a common crematorium the corpse in the coffin was introduced into the opening by means of a movable car on rollers, but in the concentration camp crematoria the corpse was introduced into the muffle on a hand-carried litter.[...]""

3 corpses per muffle equals 20 minutes a corpse. Though there have been testimonies that sometimes they would shove up to 4 emaciated bodies into one opening which would burn in the same time due to the fact that the bodies were not of normal human wieght. That would equal 15 minutes a corpse with 5 ovens operating equals 20 corpses an hour per crematorium. That would be at max operation. Pretty fucking efficient mass slaughter that.