---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Wed 12/07/11: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:49 AM - Re: Re: Auto Aux Fuel Pump Circuit Idea (Glen Matejcek) 2. 08:02 AM - Re: Re: Re: Auto Aux Fuel Pump Circuit Idea (Ken) 3. 02:15 PM - Re: Re: Re: Auto Aux Fuel Pump Circuit Idea (Kenneth Johnson) 4. 10:13 PM - Matronics Web Services Restored! (Matt Dralle) ________________________________ Message 1 _____________________________________ Time: 05:49:47 AM PST US From: Glen Matejcek Subject: AeroElectric-List: Re: Re: Auto Aux Fuel Pump Circuit Idea Hi All- I may have missed something in the exchanges here, but I think a couple data points might have been overlooked. First, one of the differences in the aircraft and automotive fuel systems is that the automotive system works at ground level. The aircraft system needs to work at lower ambient atmoshpheric pressures, and is therefore inherently more vapor lock prone than an automotive system with the same fuel at the same temperature. Another data point is that when the automotive, tank mounted pump fails, you coast over to the side of the road. It's a little more complicated when the pump in a pump dependent aircraft fuel system quits. A a reminder, the common philosophy behind aircraft boost pumps is to provide fuel pressure when the engine driven pump can't, I.E. for priming or when the EDP has failed. If an aircraft fuel system has turned out to need the boost pump in order to operate safely under nominal circumstances, I would suggest that there is another problem that needs to be addressed and that using the boost pump is a band aid, not a solution. The last thing is that the plans for my fuel injected RV called for quite a bit of seemingly unnecessary tubing in the return line back to the selector valve. Turns out that the whole point there is to provide a radiator. If one were to get creative and shorten that line, the system would end up more vapor lock prone. FWIW, YMMV, ETC Glen Matejcek ________________________________ Message 2 _____________________________________ Time: 08:02:20 AM PST US From: Ken Subject: Re: AeroElectric-List: Re: Re: Auto Aux Fuel Pump Circuit Idea > The last thing is that the plans for my fuel injected RV called for > quite a bit of seemingly unnecessary tubing in the return line back > to the selector valve. Turns out that the whole point there is to > provide a radiator. If one were to get creative and shorten that > line, the system would end up more vapor lock prone. > Actually after watching attempts to cool and reintroduce bypassed fuel into the pump end in bent airplanes, most folks agree that the issue is venting the vapour bubbles back to a tank or header. Merely cooling doesn 't cut it for automotive EFI installations. Maybe it works better with 100LL. When the pressure drops at the regulator there is excellent conditions to create vapour bubbles, some of which are air and not all of which will readily re-condense. Ken ________________________________ Message 3 _____________________________________ Time: 02:15:27 PM PST US From: Kenneth Johnson Subject: Re: AeroElectric-List: Re: Re: Auto Aux Fuel Pump Circuit Idea Hi All,=0AI seldom write because I am far from an expert in this area.- I n addition I have not finished building my plane.- However, I will offer this suggestion as it has been recommended for my engine.- I am using a M azda rotary engine.- This automotive engine has a fuel rail with a return fuel line to my main fuel tank.- With the engine, a MSD Ignition high pr essure electric fuel pump (Part # 2225) was included.- Because this is a very important part for engine function, a second pump has been plumbed in parallel with check valves for each.- There are separate switches for eac h, which allows one to use either one.- I am uncertain about using them b oth together, as I am not that far, or if would even be necessary.- These fuel pumps have been placed on the pilots side of the firewall and the fue l is pumped about 2 feet to the fuel rail. - I have looked up information regarding this fuel pump and it appears to be reliable and that is why I h ave written.- If others have experience with this fuel pump, it would be ope n for discussion.- =0A=0AKen Johnson=0A=0A=0A=0A_________________________ _______=0A From: Glen Matejcek =0ATo: aeroelectric -list@matronics.com =0ASent: Wednesday, December 7, 2011 7:45 AM=0ASubject: AeroElectric-List: Re: Re: Auto Aux Fuel Pump Circuit Idea=0A =0A--> AeroE lectric-List message posted by: Glen Matejcek =0A =0AHi All-=0A=0AI may have missed something in the exchanges here, but I th ink a couple data points might have been overlooked.- First, one of the d ifferences in the aircraft and automotive fuel systems is that the automoti ve system works at ground level.- The aircraft system needs to work at lo wer ambient atmoshpheric pressures, and is therefore inherently more vapor lock prone than an automotive system with the same fuel at the same tempera ture.=0A=0AAnother data point is that when the automotive, tank mounted pum p fails, you coast over to the side of the road.- It's a little more comp licated when the pump in a pump dependent aircraft fuel system quits.=0A=0A A a reminder, the common philosophy behind aircraft boost pumps is to provi de fuel pressure when the engine driven pump can't, I.E. for priming or whe n the EDP has failed.- If an aircraft fuel system has turned out to need the boost pump in order to operate safely under nominal circumstances, I wo uld suggest that there is another problem that needs to be addressed and th at using the boost pump is a band aid, not a solution.=0A=0AThe last thing is that the plans for my fuel injected RV called for quite a bit of seeming ly unnecessary tubing in the return line back to the selector valve.- Tur ns out that the whole point there is to provide a radiator.- If one were to get creative and shorten that line, the system would end up more vapor l =========================0A =================== ________________________________ Message 4 _____________________________________ Time: 10:13:59 PM PST US From: Matt Dralle Subject: AeroElectric-List: Matronics Web Services Restored! Dear Listers, I'm extremely happy to report that as of about 9pm PST 12/7, all of the Matronics web services have been fully restored including the Web Forums, List Browse, Archive Search, Wiki, and AeroElectric web sites. It was quite an ordeal getting the replacement boards for the server, but things went back together tonight and are up and running nicely. The first company I ordered the boards from originally called me a day later to say that, whoops, they really didn't have them in stock after all... Fortunately, I was able to locate some through a different source and had then over-nighted and they arrived today. Thank you for your patience and consideration though the whole thing! 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