In John Samuel's thread on the evils of shop vacs we discussed the merits of removing VC filters to aid flow so I decide to test this out.

Before I proceed let me clearly state the potential problems of doing this.

1) VC motor overheating
Although it appears unlikely there is a possibility that without the filters the VC motor could draw a much greater current and overheat. I you do decide to do this with a make/model of VC that has not been tested I recommend checking the power consumption with and without the filters.

2) Dust
This is bleedingly obvious but the filters should only be removed if
i) the VC is located outside the shed,
ii) it is a blower VC and the blower end is connected to a DC,
iii) the VC is placed inside a sealed chamber which is vented via a DC
i) and iii) are also likely to seriously contaminate the motor cooling loop which compromises the subsequent use of the VC if the filters are put back into the VC and the VC is then used back inside the shed.

The model of VC I tested was my 1500W Ryobi wet and dry Vac.
I emptied and washed out the VC dust bucket and removed the filter and careful knocked the bulk of the dust off and then blew the remaining dust off with a compressed air line.
I then measured the current draw and tested the flow with the freshly cleaned filters in, and then again with filters out.

Current draw was in both cases 5.0A or ~1500W.
This immediately tells me that the cleaned filters are not providing much restriction otherwise the current draw should have increased on removing the filters.

The flow rate difference between using clean filters and no filters is a whopping 6% so there is not much in it.
However as VC filters generally block very quickly within minutes of use I would expect the flow difference to be more significant
I will now leave the filters in and test what happens to flow as the filter becomes blocked over time.