--- In dmcnews@xxxx, "Walter Coe" <Whalt@xxxx> wrote: <SNIP> > The best cure, obviously, is to keep the fuel cool. The easiest place to > start is reducing the heat transfer from the coolant pipes. As you may > already know, aluminum is an excellent conductor of heat. And there isn't > much room for insulation between the pipes & the fuel tank. I suggested > before that an easy improvement would be to replace these sections of > aluminum pipe with long pieces of silicone hose <SNIP> Yes, I figure that it is the coolant pipes that are heating the tank up. Another member off of the list did reccomend to me trying the exhaust wrap for the pipes. So this too is an option that I'm looking into. I really don't want to replace the existing aluminium pipes with rubber hoses. This just worrys me in as it's two more items that I have to worry about rotting/replacing in the years to come. <SNIP> > > Now, from all this, I have determined the following: > > 1. A noisy fuel pump isn't always due to a collapsing fuel pick-up > > hose. > > You got that right! I installed a spring in my hose, too, and it seems to > only make the problem worse -- by conducting the sound better and by > producing more restriction/turbulence. <SNIP> Add to this the fact the spring is yet another component to be installed. I stand behind it in as it is a fix that can keep the fuel hose from collapsing, but it is not what I would consider a permanent solution for my issue. I'm currently working on a way to not only remove the spring from the equasion, but the entire pickup hose as well. The less parts, the better, and I'd like to remove the main source that started this problem in the first place. <SNIP> > > 2. Air flow from the front radiator is NOT heating the fuel. When I > > stopped the air flow, the noise became worse. It wasn't until I > > restored air flow that there was a sign of cooling. > > This contradicts what I've read about installing an air dam. I would like > to hear more about your theory here. I have found that once the fuel gets > hot enough to cavitate, it stays hot for a long time. <SNIP> I have thought about this, and have come up with a couple of theories: 1. Air flow is what is sufficient to cool the tank down. or 2. The coolant pipes on both sides of the radiator are transfering heat thru the fuel. Gasoline is absorbing heat from the source pipe, it then travels thru, and is reabsorbed by the cooler return pipe. While parked, the tank absorbed heat from the hot line, but was unable to lose the heat fast enough because cooler pipe had no water flow to carry the heat away. But once I drove a couple of miles, the temperatures recooled to the "balanced" level they were at before. Now, to add to this, another possibility that has crossed my mind: Does heat directly transfer from the water pipe into the gastank? Or, is the heat absorbed thru the plate below protecting the gas tank? If the bottom plate is absorbing the heat, this would make total sense! Heat being transfered thru would turn the sheild protecting the gastank into a huge "hotplate"! And the reason that we would not see these same kind of symptoms in the winter is because the metal plate is able to transfer heat much easier than the composite material in the gas tank. Just like electricity, heat would transfer thru the path of least resistance, and would be absorbed by the ambient air flow under the car! In any case, air flow from the radiator is NOT the culprit of hot fuel tanks. IMO, the DeLorean has one of, if not the best radiators for cooling the engine. Other vehicles typicly push air into the engine compartment, and it has not other choice but to exit out of the bottom of the car. With the DeLorean, hot air flows out thru each of the front wheel wells, as well as the bottom. Not just for the coolant, but the A/C always cools down quickly, and stays cold! Putting the air dam in place is not a good idea. It's a waste of money, it can cause vapor lock-up @ high speeds, and has no impact on the fuel tank at all. Only a VERY small portion of the top on the fuel cell is actually exposed to air from the radiator. <SNIP> > This thought has crossed my mind too. (briefly :-) I envisioned a fuel tank > cover made of aluminum with heat-sink fins running the length of it. Then > you would need a really big smear of heat sink compound between it and the > tank. (Yeah, right :-) <SNIP> Don't laugh just yet, that may just be the thing we need. I don't know how we could attach fins to the bottom plate, but it should do the trick to rid the tank of excess heat. The only question I would have is how well does the compound adhere to things? If removal of the tank were nessisary in the future, You'd want to make sure that you could easily seperate the two. <SNIP> > Another thing to consider is using an inline fuel radiator. A nice spot for > one would be in the frame next to the fuel accumulator, but there isn't much > room for air flow through here. There is plenty of room in the engine > compartment, but instead of stagnant cool air we have turbulent hot air. <SNIP> I don't think that a fuel radiator of any sort sould be nessiasry at all. Even if you installed one, I don't believe that it would allieviate the problem. It would cool the fuel behind the pump, and that isn't where the heat source is at. Rather than trying to keep hot fuel cool, let's keep the fuel from getting hot at all, and use the heat sink on the bottom to rid the gas of any stray heat that may have entered. Although if we insulate the water pipes, and remove the pickup hose to kill the noise, we may not even need to go to that far of an extreme with the bottom plate. <SNIP> > On a more sarcastic note, it almost seems a shame that they go to the > trouble to plumb coolant from the engine to the heater core when they could > have instead substituted hot fuel. All the heat you would ever need could > be taken from the fuel return line. :-) > Walt I don't think that the engineers had thought of this problem of hot gas comming up. At least not in the kind of hot environments that our cars are in. It has to be the bottom plate acting as a heat sink in cold weather that keeps the fuel cool. Otherwise, Noisy fuel pumps would be a problem on EVERY DeLorean on the road. -Robert vin 6585 "X"