This is something I've tried on several occasions now and it appears to speed the conversion.
With my warren of contorted pipes on the processor, I'm able to run Frankinpump against a partially closed discharge valve. With the oil/bio at around 30°C I usually get around 1 Bar pressure against the venturi, but by partially closing a valve on the discharge of the pump I can comfortably generate 4 Bar (and considerable noise ... it's a ball valve) whilst maintaining a reasonable flow.
The extra turbulence appears to give quite an improvement in time to completion. Anyone else in a position to give this a try and confirm?