| Jack, what you describe below sounds like pin 4. Did you happen to determine what pin 13 does exactly?
Also, in case there is anyone out there that does not have A/C, another use of pin 4+vac is to open the outflow valve fully to maximize fresh air flow through the cabin when not pressurized. For this you would need a manual switch to pin for which bypasses the usual gear/airspeed interlock.
Colyn On Oct 10, 2013, at 7:39 AM, Jack Morgan wrote: Hello Dico,
I talked directly with Dukes engineering while I was sorting out my IVP. The only function the vacuum performs is to fully open the valve when the dump solenoid is activated. Dukes advised that providing vacuum was optional and not a requirement for proper operation. Graig correctly describes the system behavior without vacuum. I did not opt for the complexity of an electric vacuum pump and get the same slight pressure bump Craig describes if throttle is firmly advanced on takeoff.
So....... the addition of an electric vacuum pump is up to the builder. I doubt most pilots would be able to ascertain that the pump had failed during their normal operations. The vacuum is not required for proper valve operation if the dump valve solenoid is activated for some reason during flight. If you choose to go without vacuum, Dukes advised you close off the port with an appropriate sealing method. Regular servicing of the filter is not required if you omit the vacuum.
If you choose to go with a vacuum pump, make sure the dump valve is properly wired so it is activated with the gear down or else you will not get the slight (and only) benefit from the pump on takeoff.
Jack Morgan On Oct 10, 2013, at 6:01 AM, Lancair Mailing List wrote: I have an all-electric airplane as well and chose to not have any vacuum supplied to the Dukes valve. The only difference is the rate in which pressurization starts building in the cabin on takeoff roll. Once airborne, vacuum has no effect on the pressurization system. I choose to apply power a little more slowly than some pilots. This prevents any pressurization discomfort and typically I don't need any right brake to hold centerline. Takeoff distance is not an issue. If I can land there, I can easily takeoff there. I know one pilot who has developed an electronic circuit to control a small electric vacuum pump based on the landing gear position. So there are several options. In my opinion, keeping the engine driven pump is the least desirable.
Craig Berland
N7VG
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