![]() ![]() The electric pumps associated with AFP, EFII and SDS fuel systems do not like vapor bubbles, and you can hear them complain mightily when bubbles come into the suction line. On my IO360, I ended up installing larger, higher flow rated prefilters to get the pressure drop down for the fuel flowing across that filter. The higher vapor pressures associated with those fuels (especially winter blend) will make them susceptible to forming vapor bubbles in the pre-filter with a pressure drop across the filter. Where I think you may find some issues is with folks that are running automotive fuels with ethanol. ![]() It is recommended to use a 40-micron maintainable filter in composite aircraft applications. This maintainable filter incorporates a 125 or 74 micron pleated stainless steel filter element with a anodized aluminum housing. The filter Airflow Performance recommends for this application is P/N1090079 or 1090079-74. ![]() This again depends upon the type of fuel system in the aircraft, returning or non-returning. The filter size must be based on the total fuel flow through it, not just the engine fuel consumption. This problem is not as evident when float carburetors are used, since the float chamber will allow the fuel vapor and bubbles to escape. If the inlet of the fuel pumps are restricted, the pressure on the inlet becomes depressed, this will cause the fuel to boil and the vapor will flow into the fuel controller causing it to malfunction. Paper element filters will restrict the inlet of the fuel pumps due to their fine filtration and their susceptibility to clogging from picking up water. Airflow Performance does not approve the use of any paper element type fuel filter. If this type of device is used, then the gascolator should be installed at the lowest point in the fuel system. The filter may also incorporate a gascolator. (Replaceable or cleanable filter)Ī fuel filter should be installed in the system before the fuel boost pump, and after the selector valve. (It does not have AN6 fittings built into the billet housing) Also being able to easily inspect the filter would be good. Personally, I like filters with AN6 fittings already built in on each end without the use of extra fittings but once more the Holley filter is fine. For me as long as the filter has the capacity (filter sq footage) and capability to filter fines (The finer the better in my book) I will use it. The rest of us need to understand what our injectors can tolerate and go from there. Ross is a very good engineer and he understand the limits his injectors can withstand. After the pump we don't need to worry as much about pressure drop as the pump can deliver 2- and 3-times more positive pressure to overcome a tighter filter. I worry more about insuring we get a sufficient amount of fuel to the suction side of the pump than most other issues. ![]() Heat, altitude, pressure drop (elbows, low micron filters), mix in mo-gas and we create lower vapor pressure and then the dreaded cavitation. Since the maximum pressure that the suction side of a pump can generate is -14.7 psi and anything close to this reduces the vapor pressure and creates cavitation in the system. The dual electric fuel pumps used on the 2 major EFI systems use a pump that is not very tolerant of air in the system and cavitation. All of us are using different types of pumps, injectors etc., and some are more susceptible to cavitation and other issues. We need to understand and choose what we are comfortable with. A MK4 system with an inlet diameter of 4" is also available if required.īoth the MK3 and the MK4 are 10" in length and may be trimmed to 9" at the intake.This article describes in general requirements and possible data for filter choices. The MK3 induction system intake volume is sufficient for engines up to and including IO-540. The MK3 filter unit has no provision for carb heat but allows for an alternate air door "downstream" from the filter. If you're using a fuel injector servo on an updraft engine, we combine the MK3 filtration unit with the same air sweep box used with the carbureted engines. The kit does not include rivets or alternate air door control arm. Parts are raw components and need to be assembled by the builder. The kit is comprised of the following components which are also available individually: Our MK3 ram air induction kit is designed for use with fuel injector servos (forward facing/parallel or updraft). Fuel Injected Engines MK3 Ram Air Induction Kit (Forward facing or updraft) ![]()
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