I had to do some quick math- 16 liters is around 4.22 gallons
I would not focus on the temperature so much:
Here is what I do:
Crank the heat on the still until it starts producing
Once it starts producing turn the heat down until I have a 5-8 drips a second (just below a trickle)
Dump the first 150-300ml on a 5 gallon run as this will contain a higher percentage of methanol
Collect and label jars while making cuts during the run
It sounds like you were running really slow- I will run 5 gallons in about 6-8 hours with my clawhammer still. I also run my still until the product is at 20%. I will collect between 1-1.5 gallons of total product in 6-8 hours- this included heads,hearts,tails.