Return-Path: Received: from [24.25.9.103] (HELO ms-smtp-04-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.3c1) with ESMTP id 743796 for flyrotary@lancaironline.net; Thu, 17 Feb 2005 22:09:55 -0500 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.103; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-185-127.carolina.rr.com [24.74.185.127]) by ms-smtp-04-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id j1I397Ci026049 for ; Thu, 17 Feb 2005 22:09:08 -0500 (EST) Message-ID: <005201c51567$3973eac0$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Returnless Fuel System - Fuel Cooler Date: Thu, 17 Feb 2005 22:09:13 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Virus-Scanned: Symantec AntiVirus Scan Engine Well, perhaps you are correct, Leon (about the climate part - not the lunatic part {:>)0 . However, I live in the Southeast US where temperatures do get above 100F and have flow with my system for over 260 hours. Early on I did experience some fuel vapor perturbations, but found that the boost pump always did away with them. More importantly, I found that once I put a shield around my Sump tank and routed some cooling air to the box I have not encountered any such problems. I don't advocate the system for use as I have found that most people who "copy" a design which works, really don't copy it faithfully. Any change made of course means they are dealing with a "new" design which may not function like the model they based it on. Given the frequency with which people have run into vapor problems, I would have to agree with your statement that a system which returns fuel to a main tank (heat sink) is clearly less likely to have any vapor lock type problems. So anyone in the design stage of their fuel system should certainly give serious thought to a "returned fuel" system. Best Regards Ed A ----- Original Message ----- From: "Leon" To: "Rotary motors in aircraft" Sent: Thursday, February 17, 2005 8:52 PM Subject: [FlyRotary] Re: Returnless Fuel System - Fuel Cooler > Hey Guys, > > I'm sort of having trouble believing that this discussion is still going on > about returnless systems. Why?? Todd probably gets away with his system > because > he lives in a REALLY cold climate. He would DEFINITELY have SERIOUS > problems in the 50 Deg C heat we regularly expereience on the tarmac here in > Oz in summer. But then again, maybe Lamar IS correct, and that I AM a > lunatic!! > . > For the power output that most of you have (less than 250 BHP), a 5/16" > high > pressure supply line is more than adequate, and a 1/4" return line is more > than adequate. For bigger power output (Hi Boost 13B & 20B engines, say up > to 400 Cheveaux) and a Hi Flo EFI pump , maybe a 3/8" supply line, and a > 5/16" return line. > > Whenever I do a turbo engine conversion on ROAD GOING early model RX7 > ('79-"85), I just use the stock fuel lines (5/16" supply & 1/4 return), > and I have never have a problem. One EFI pump is sufficient. The > only reason we have 2 x HP pumps on an aircraft is redundancy in case one > fails at take-off and climb-out. > > However, the size of the return line is not really that critical. All it is > there for is to take the flow from the dumped pressure from the HP pump. If > you are using the same pump as a car, then you only need the same size > return. > Interestingly, on the Mazda RX7 turbo cars, they have a 2 stage control > (via voltage) of the EFI pump to cut the return flow at low load, and boost > the supply at high load.. > > The SIZE of the return line is not really so much an issue as actually > having one - size is more of an issue with the supply line, but only with > Mega-Pferd turbo engines. The issue is that so long as there is a return > line so that > the fuel continues to circulate back to the tank, and if that tank is in > the breeze, the fuel will never get hot. > > If the fuel is returned to the header / surge tank, this MUST be vented > back to the main tank. Otherwise you will get air/vapour locks. If there > is a breeze directed over the header/surge tank, then why do you need a $40 > cooler?? As a famous megalomaniac once said, "It's either them or us" > (referring to issues of mental stability). > I'm just totally flummoxed. > > As Tracy said below, the cooler is just a bandaid covering up a problem. > It also scares me witless when I read what Tracy wrote below about a > fatality actually occuring because of dicey fuel supply issues. > > So please, ... this is a plea, just follow normal EFI practice. > Have a look at the Toyota PDF link somebody posted a while ago about both > return & returnless systems. Stick to the return system. This is the way > it MUST be done. Please DON'T > try to re-invent something that doesn't need to be re-invented, and that > has been proven to work on millions of EFI road cars, and thousands and > thousands of race cars. > > Additionally, that SDS link I posted the other day details how to do it > where there are multiple tanks involved. There is a "critical minimum > complexity" in any system. Try and simplify the system any further beyond > this "critical minimum complexity", then the system no longer works > properly, and will come back and bite you REALLY hard on your nethermost > parts when you least expect it! > > Cheers, > > Leon > > > ----- Original Message ----- > From: "Bob White" > To: "Rotary motors in aircraft" > Sent: Friday, February 18, 2005 2:29 AM > Subject: [FlyRotary] Re: Returnless Fuel System - Fuel Cooler > > > > > > Hi Tracy, > > > > My alternative is to try to jam all the return fuel thru a 1/4 inch > > line. It seems like that will cause problems also. It's fairly > > substantial surgery to get a 3/8 inch return line in. > > > > I certainly agree that without the cooler it's a disaster waiting to > > happen. I'm relying somewhat on Todd's positive experiences > > with his system, and further testing on my plane. > > > > Bob White > > > > On Thu, 17 Feb 2005 09:52:56 -0500 > > "Tracy Crook" wrote: > > > > > Even with the cooler, This scares me. I know of at least 2 cases > where it has caused power failures, one resulted in fatality. True, they > didn't have the cooler but it is a bandaid covering up a problem. > > > > > > Tracy > > > > > > Hi Jim, > > > > > > Todd's system is a "quasi" returnless system. The fuel is returned to > > > the input of the fuel pump instead of the tank. Without the cooler, > > > much of the same fuel would circulate thru the fuel rail again and > agin > > > picking up heat. To see Todd's diagram and description go to: > > > > > > http://www.rotarywiki.com/ and search for > "returnless". > > > > > > Bob White > > > > > > > > > On Wed, 16 Feb 2005 23:25:06 -0600 > > > Jim Sower > > wrote: > > > > > > > But I thought the purpose of the cooler was to cool the *return* > fuel. > > > > If it's a one-way system, how does the fuel get hot enough to need > cooling? > > > > What am I missing here? ... Jim S. > > > > > > > > Bob White wrote: > > > > > > > > >Todd, > > > > > > > > > >I'm going to build a returnless system based on your design. I > found > > > > >this fuel cooler at Jeg's for about $40. Jeg's P/N 771-1009. The > > > > >finned area is 4.5 X 5 X 7/8 (inch), which I think is a little > bigger > > > > >than the one you made. > > > > > > > > > > >http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=3532&prmenbr= > 361 > > > > > > > > > >I'm sure it's nicer looking than anything I could build myself. > I'll > > > > >post pictures of my alternator bracket one of these days to prove > it. > > > > > > > > > >Bob White > > > > > > > > > > > > > > > > > > > > > > > >> Homepage: http://www.flyrotary.com/ > > > > >> Archive: > http://lancaironline.net/lists/flyrotary/List.html > > > > > > > > > > > > > > > > > -- > > > http://www.bob-white.com > > > N93BD - Rotary Powered BD-4 (real soon) > > > > > > >> Homepage: http://www.flyrotary.com/ > > > >> Archive: > http://lancaironline.net/lists/flyrotary/List.html > > > > > > > > > -- > > http://www.bob-white.com > > N93BD - Rotary Powered BD-4 (real soon) > > > > >> Homepage: http://www.flyrotary.com/ > > >> Archive: http://lancaironline.net/lists/flyrotary/List.html > > > >> Homepage: http://www.flyrotary.com/ > >> Archive: http://lancaironline.net/lists/flyrotary/List.html