---------------------------------------------------------- AnPMech-List Digest Archive --- Total Messages Posted Sat 12/17/05: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 10:40 AM - Re: Automotive man goes AIR Motive (Brinker) 2. 01:09 PM - Re: Automotive man goes AIR Motive (FLYaDIVE@aol.com) ________________________________ Message 1 _____________________________________ Time: 10:40:55 AM PST US From: "Brinker" Subject: Re: AnPMech-List: Automotive man goes AIR Motive --> AnPMech-List message posted by: "Brinker" I was told that on the IO540 or any other Lycoming fuel injected engine that they required only 4-5 psi to operate the injection system. And that that was what the mechanical fuel pump was rated at. Which was astonishing to me since I only have experience with automobile type injection systems that normally have 40 psi plus to operate. Is the 4-5 psi correct ? If so with lets say 40 gallons of fuel in each tank I would think that gravity would supply at least close to this type pressure out of a 3/8 line. Although I have not done a test to show this. I believe I will though at a future date just to satisfy my curiosity. I have a 94 model Chevy pickup that we recently changed the throttle body design 350 engine over to a multi port fuel injected LT1 engine. We did change the fuel pump to the proper pump for that engine during installation. Was told the proper pump needed to put out 50-60 psi for the LT1. We still have not gotten the bugs out of the system yet to get the engine to run consistently. We have changed several sensors that we're suspect and still it was not running consistent. Finally we did a fuel pressure check to discover the new fuel pump was weak and only producing around 7-9 psi. Have yet to change pump since it is a bear to replace since it is in the fuel tank. I am still driving the truck I just cannot use full throttle or at times (not all the time) will act as though the fuel shut off and it fall's on it's face. What I am getting at is that the pump is putting out anywhere from at least 40-50 psi less than the required pressure but the vehicle is still drivable and has sufficient power for normal driving. To me this is very interesting and indicates that "perhaps" all FI engines will operate on lower than published pressures. If this is true and the Lycoming only needs 4-5 psi to operate nomally (which I still have'nt verified) then the IO540 "should" run on much less than the 4-5 psi. Which would not be much. I will still install the boost "safety" pump on my Comp 6 just for peace of mind and for quicker easier starting purposes. Does anyone out there have the psi spec's on a IO540 or other FI aviation engines ? Thanks Randy ----- Original Message ----- From: "Marvin Dupree" <97corvette@cox.net> Subject: Re: AnPMech-List: Automotive man goes AIR Motive > --> AnPMech-List message posted by: Marvin Dupree <97corvette@cox.net> > > the wings would have to be very high to provide the pressure required > for fuel injection. hence the boast pump. > marvin m20e > On Dec 16, 2005, at 8:38 PM, FLYaDIVE@aol.com wrote: > >> --> AnPMech-List message posted by: FLYaDIVE@aol.com >> >> In a message dated 12/16/05 1:31:24 PM Eastern Standard Time, >> brinker@cox-internet.com writes: >> >>> Maybe Cessna is confident enough to not have boost pumps on their >>> high wing planes >> ================== >> I don't know about ALL Cessnas, but the C-177 Cardinal has a boost >> pump and >> it is a high-wing >> >> Barry >> "Chop'd Liver" >> >> > > > ________________________________ Message 2 _____________________________________ Time: 01:09:20 PM PST US From: FLYaDIVE@aol.com Subject: Re: AnPMech-List: Automotive man goes AIR Motive --> AnPMech-List message posted by: FLYaDIVE@aol.com Randy: I have enclosed my responce within the body of your eaml. Please read on. Barry ================================= In a message dated 12/17/2005 1:41:44 PM Eastern Standard Time, brinker@cox-internet.com writes: I was told that on the IO540 or any other Lycoming fuel injected engine that they required only 4-5 psi to operate the injection system. And that that was what the mechanical fuel pump was rated at. Which was astonishing to me since I only have experience with automobile type injection systems that normally have 40 psi plus to operate. Is the 4-5 psi correct ? ------------------------------- I must plead ignorance of the automotive fuel injected system. But my question would be is that Supply Fuel pressure form the fuel tank or INJECTION PRESSURE? I know diesel systems use about 1000 to 3000 PSI for their fuel injection system. ================================================== If so with lets say 40 gallons of fuel in each tank I would think that gravity would supply at least close to this type pressure out of a 3/8 line. Although I have not done a test to show this. I believe I will though at a future date just to satisfy my curiosity. Gravity pressure is VERY nil. Here are some numbers to use: A column of water 1 FOOT (12") of high will develope 0.432 PSI at sea level. Take the height of the gas in the wing at the wing height and SUBTRACT the Height of the Fuel Bowl above ground, and that will give you the potential height. Now multiple that by 0.432 and that is how many PSI of fuel pressure you will develop. Well, not really .... REMEMBER FUEL weights less than water. Water = 8 Lbs/Gal and Fuel = 6 Lbs / Gal. If you want to you can work out a ratio. ======================================================= I have a 94 model Chevy pickup that we recently changed the throttle body design 350 engine over to a multi port fuel injected LT1 engine. We did change the fuel pump to the proper pump for that engine during installation. Was told the proper pump needed to put out 50-60 psi for the LT1. We still have not gotten the bugs out of the system yet to get the engine to run consistently. We have changed several sensors that we're suspect and still it was not running consistent. Finally we did a fuel pressure check to discover the new fuel pump was weak and only producing around 7-9 psi. Have yet to change pump since it is a bear to replace since it is in the fuel tank. I am still driving the truck I just cannot use full throttle or at times (not all the time) will act as though the fuel shut off and it fall's on it's face. What I am getting at is that the pump is putting out anywhere from at least 40-50 psi less than the required pressure but the vehicle is still drivable and has sufficient power for normal driving. To me this is very interesting and indicates that "perhaps" all FI engines will operate on lower than published pressures. If this is true and the Lycoming only needs 4-5 psi to operate nomally (which I still have'nt verified) then the IO540 "should" run on much less than the 4-5 psi. Which would not be much. Randy, there is something else that you MUST consider. VOLUME OF FLOW! What size fuel lines are in the car? I'd bet dollars to donuts that they are NOT 3/8". I'd bet that they are 1/3 that diameter ... 1/8" Diameter. So you would think that a 1/8" fuel line would require MORE pressure ... WRONG! Why? Because the fuel flow requirements in a car is in direct proportion to HP. YES, some cars have TWICE the HP of our planes BUT! They do not run at 65 - 75 and 100% of their HP as a plane does. A car cruising at say 75 MPH will use only about 20 HP in flat road cruse. I use to race a Buick Skylark Custom, it had a 350 CID engine. I wanted more HP so I went to Dual 650 Holly's. I LOST POWER and sometimes stumbled. Why? Because the Dual 650 Holly's required MORE air flow and MORE FUEL ... I had to install a fuel pump back at the gas tank. That may be the problem you are having with your pickup. ======================================== I will still install the boost "safety" pump on my Comp 6 just for peace of mind and for quicker easier starting purposes. Does anyone out there have the psi spec's on a IO540 or other FI aviation engines ? If you are serious about this engine I would get the Maintenance and Parts Manual from Lycomming. I'm sure this information would be in there. Barry "Chop'd Liver" ========================================== Thanks Randy Barry "Chop'd Liver"