Roggaman Posted March 19, 2004 Share Posted March 19, 2004 I want to make sure that my engine in my 280ZX gets enough fuel, even when I'm racing it, so I'm going to use the stock fuelpump in the back to deliver fuel to a catchtank placed where the battery used to be. From the catchtank I'm letting a Bosch highflow pump deliver the fuel to the fuelrail and the excessive fuel is routed back to the catchtank. But I also need a return line from the catchtank back to the stock fueltank. So now to my question: To raise the pressure a little in the catchtank, I want a small orrifice in the returnline, anyone know a suitable size on the orrifice? (Hope I made myself clear, some technical expressions don't always come out right since english is my second languish) Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 20, 2004 Share Posted March 20, 2004 Just put a carb fuel pressure regulator on the tank. I have mine set at about 2 lbs. Bought and adjustable reg at local auto parts store for about 20 bucks. Mark Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted March 20, 2004 Share Posted March 20, 2004 I think you guys may be confusing concepts here. Pressurizing a tank, and fuel pressure through a line are two different things. The fuel pressure through a line is the rate that the fuel is moving through the line. You cannot apply that same pressure to pressurizing non-moving fuel in a fuel tank (liquids cannot be compressed). To pressurize the fuel tank you need to have pressurized air. A regulator will just keep the fuel from flowing out as fast as it flows in, it will not produce pressure in the tank other than the resulting displacement of the air due to the quantity of fuel in the tank. Think of fuel pressure as basically a by-product of air-pressure. What might work to pressurize the tank would be to have something that is basically a bag of compressed air in the small tank that would hold the same amount of air no matter what. When the fuel comes in and compresses the bag of air further, the air will get pressurized and in turn put pressure upon the fuel. I would assume that this could be very dangerous, so I'd pay very close attention to what the maximum pressure would be within the tank. It would be very messy if the bag were to exert enough pressure on the fuel in the tank to create combustion. Pretty, but messy. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 20, 2004 Share Posted March 20, 2004 Roggaman, The pressure reg on the tank will work, I don't know the physics behind it but I do know it works, It's on the car, checked with a pressure gauge and it will hold the pressure that the regulator is set to. I would run a return line from the surge tank back to the fuel tank. Put the regulator on the exit of the retunr line from the surge tank to the stock fuel tank. Hope that helps. Mark Quote Link to comment Share on other sites More sharing options...
Roggaman Posted March 22, 2004 Author Share Posted March 22, 2004 Yes Mark, I'm with you on this one. I know that pressurizing a tank is doable with a regulator, but I don't want to use one, so I guess I just have to calculate the size of the hole to create just the right pressure in the tank. -Nic-Rebel450CA : Food for thoughts. If you made a fuel line thicker and a fuel tank smaller, at what point do you suggest that the fuel line will lose pressure and the tank gain pressure!? Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted March 22, 2004 Share Posted March 22, 2004 Mark, What is happening is that the catch tank is getting filled up completely (no air space). Once that happens, all you have is basically an extension of a normal fuel line. The pressure is coming from the pump that is pumping the fuel through the fuel rail and the resultant expansion of the fuel lines, the regulator is then simply limiting the rate at which the pump pumps the fuel back to the primary fuel tank. Essentially all you are doing is putting a low pressure fuel regulator in line after a fuel injection pump which is asking for serious trouble. The fact that you have a catch tank which makes the amount of fuel between the pump and the pressure regulator even greater in volume just makes it that much more dangerous. Putting a 2lbs limit on an FI system is guaranteed to explode, yes, guaranteed. I cant promise you when, but I can promise you that it will. If that regulator is not rated for use on an FI system (which it probably is not), I would HIGHLY recommend that you remove it immediately. Roggaman, My suggestion would actually be to not use any form of regulation at all unless you can find a regulator that matches the output of your fuel pump. The catch tank will hold more than enough fuel in it to serve as an excellent resevoir without needing to dangerously put in regulators to try to keep the fuel in. Why not just put a higher capacity fuel pump in place of the stock fuel pump and use a normal fuel system. The gas tank gets pressurized by the gas fumes and certainly holds plenty of fuel. If you are insistant on doing this catch tank setup, my suggestion would be to make an outlet on the tank for the line returning to the primary tank just slightly smaller in diameter than the incoming line. This will help maintain the pressure in the catch-tank, without significantly increasing the risk of rupture. Just make sure that all components of the fuel system can withstand the maximum pressure that the fuel pump is capable of forcing. As mentioned earlier, if the catch tank were to rupture, there would be a serious problem. As for the food for thought, I am not sure I understand your question. If you care to restate I'd be happy to help. As a refresher on physics: Fuel is a liquid, liquids cannot be compressed, this is a LAW. When fuel has pressure, it is because the fuel pump has pumped in fuel to slightly expand the fuel lines and any other part of the fuel system that can expand. The pressure is then returned to the fuel by the force of the lines trying to return to their normal diameter. (action gives equal and opposite reaction, basic physics) If you are trying to "pressurize fuel" in a container that does not have any expansion capabilities, the weakest link will expand until it ruptures. If, theoretically, there was no part of the fuel system that could expand and the fuel system was full of fuel, there would be zero pressure (except that of gravity pulling the fuel towards the Earth). Sorry if this refresher touches upon points you are already familiar with, I just wanted to make sure that the information is here before someone gets hurt or killed by an exploding fuel system. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 22, 2004 Share Posted March 22, 2004 Putting a 2lbs limit on an FI system is guaranteed to explode, yes, guaranteed. I cant promise you when, but I can promise you that it will. If that regulator is not rated for use on an FI system (which it probably is not), I would HIGHLY recommend that you remove it immediately. I don't type fast enough to respond to this, It works, it has for 8 years and It will not explode. Nuff said. Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted March 22, 2004 Share Posted March 22, 2004 Mark, I STRONGLY urge you to seek more information before you assume that there is nothing wrong with that setup and give people advice to follow it. Hopefully enough people will chime in here to help. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 22, 2004 Share Posted March 22, 2004 Nic, I don't know you, you don't know me or anything about me, for all you know I could be Stephen Hawking just lurking and sometimes posting. I don't post much but when I do, I,m pretty sure the advice is sound, in this case, the advice I gave came from real world on the car experience. Adding 2lbs of fuel pressure to a system designed to handel pressures of a FI system will not cause an explosion unless some one drops a match in the fuel cell. I don't plan on doing that and I doubt Roggman will either. Thanks for your concern. Mark Quote Link to comment Share on other sites More sharing options...
Roggaman Posted March 22, 2004 Author Share Posted March 22, 2004 Hopefully enough people will chime in here to help. Meanwhile, Mark, myself and 1000's of racer will continue to use this setup since it works. Come back when (read IF) a FI systems blows up because you put a regulator on the return. I have a bigger fuel rail in aluminium (acting somewhat like a small "tank") and on the return I have a regulator (a normal configuration) ... Following your discussion means I'm sitting on a bomb, and so are everyone else using this setup... Don't think so!! Quote Link to comment Share on other sites More sharing options...
Guest Fredrik280zx Posted March 22, 2004 Share Posted March 22, 2004 I´m with Mark and Roggaman on this one. Quote Link to comment Share on other sites More sharing options...
dmyntti Posted March 22, 2004 Share Posted March 22, 2004 I don't think the regulator would create a problem as long as it does not restrict flow in the return line to a point that the tank gets overpressurized. I would not however atempt to use an orifice for this because the fuel flow through the return varies and with the orifice so will the pressure in the tank which may get excessive. Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted March 23, 2004 Share Posted March 23, 2004 Meanwhile, Mark, myself and 1000's of racer will continue to use this setup since it works. 1000's of racers also add huge turbos to their cars with no upgrades to the FI system and no intercooler, that doesnt make it safe. Come back when (read IF) a FI systems blows up because you put a regulator on the return. I havent seen any news stories on this, but I am sure it has happened. Maybe I will check the Darwin awards site. [b']Don't think so!![/b] Come on, even high-school students working at little auto parts stores know that you cant put a carburetor regulator on an FI system. I'll leave with this since there is false information in this thread being given as supposedly correct and safe. I've given enough information to help you, if you choose not to go with it then I can rest easy, as long as I am not anywhere near your car while your fuel pump is on. This is to anyone reading this thread as a possible resource... PLEASE check with a professional before making any modifications to your fuel system. Improper modification is dangerous, and can hurt or kill you as well as others around you. Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted March 23, 2004 Share Posted March 23, 2004 Adding 2lbs of fuel pressure to a system designed to handel pressures of a FI system will not cause an explosion BTW, this is correct, IF, as I mentioned earlier, the regulator is also designed to handle the pressures of an FI system. A standard carburetor regulator is not designed to hold back the 100PSI+ that an FI system produces. (Typically the regulators are rated to about 13PSI max). Quote Link to comment Share on other sites More sharing options...
Roggaman Posted March 23, 2004 Author Share Posted March 23, 2004 Meanwhile' date=' Mark, myself and 1000's of racer will continue to use this setup since it works.[/quote']1000's of racers also add huge turbos to their cars with no upgrades to the FI system and no intercooler, that doesnt make it safe. Maybe the teenagers in the neighberhood do, but not proffesional racers... They (proffesional racers) do however use the setup me and Mark are talking about. Come back when (read IF) a FI systems blows up because you put a regulator on the return. I havent seen any news stories on this' date=' but I am sure it has happened. Maybe I will check the Darwin awards site. [/quote'] Chanses are, you’ll end up finding your own name somewhere.... [b']Don't think so!![/b] Come on' date=' even high-school students working at little auto parts stores know that you cant put a carburetor regulator on an FI system. [/quote'] Yes, and every infant (well, almost) know that it’s becuse the regulator for a carb works with a smaller gap of regulated pressure (max 8-10psi, compared to a FI’s max 85-100psi). BTW, this is correct, IF, as I mentioned earlier, the regulator is also designed to handle the pressures of an FI system. A standard carburetor regulator is not designed to hold back the 100PSI+ that an FI system produces. (Typically the regulators are rated to about 13PSI max). This is definetly were it shines trou that you don’t know what you’re talking about. It’s the regulator that builds the pressure! If you would use a carb regulator on a FI system you would never see high pressure.... And if you skipped the regulator there would be almost no pressure at all. (the only pressure built up will be from frictional losses in hoses etc). To make it really clear: The pump produces flow, the regulator produces pressure!! I'll leave with this since there is false information in this thread being given as supposedly correct and safe. I've given enough information to help you, if you choose not to go with it then I can rest easy, as long as I am not anywhere near your car while your fuel pump is on. Well, what do I know... I’m only a technical engineer, competing with cars at track days and building competition engines for a living.... I mean what do I know, I haven’t won a single Nobel price..... This is to anyone reading this thread as a possible resource... PLEASE check with a professional before making any modifications to your fuel system. Improper modification is dangerous' date=' and can hurt or kill you as well as others around you.[/b'] Yes, please check with a professional before making any modifications to your fuel system. (is this the first time you’re being right in this tread??). And if you don´t consider me being a proffesional (as I said, building competition engines for a living), please check with someone else! Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted March 23, 2004 Share Posted March 23, 2004 Roggaman, I apologize if I made you angry in some way. I wasnt trying to challenge your knowledge, I was simply providing information that was missing and explaining how unsafe such a modification can be. Just relax, everyone is here to help I wont argue against your last statements. Regardless of how incorrect they are, I have given enough information to help, and, most importantly, enough advice to hopefully keep others from making mistakes of their own after reading this thread. If anyone needs any more information they are welcome to PM or email me. Maybe you will at least accept this recomendation: http://store.summitracing.com/product.asp?d=13&s=97&p=1463&searchtype=ecat Good luck on the raceway Quote Link to comment Share on other sites More sharing options...
Guest Fredrik280zx Posted March 23, 2004 Share Posted March 23, 2004 Maybe you will at least accept this recomendation:http://store.summitracing.com/product.asp?d=13&s=97&p=1463&searchtype=ecat That´s something we all can agree on Quote Link to comment Share on other sites More sharing options...
johnc Posted March 23, 2004 Share Posted March 23, 2004 I went back and read Roggaman's first post and am confused by the setup. The general design is sound and is used often because most high pressure FI fuel pumps don't draw well, they are much better at pushing fuel. But I don't know why you would route the return line to the catch can and then back to the fuel tank. I've plumbed a few of these systems on race cars and here's the routing: Fuel Tank > feed line > high volume/low pressure pump > fuel pressure regualtor (2 to 5 psi) > feed line > surge tank > feed line > high volume/high pressure fuel pump > feed line > fuel rail > fuel pressure regulator (43 psi) > return line > fuel tank. No restriction is needed in the return line. FYI... most surge tank installations exist to solve fuel pickup problems in drag and road racing. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 23, 2004 Share Posted March 23, 2004 edit Quote Link to comment Share on other sites More sharing options...
johnc Posted March 23, 2004 Share Posted March 23, 2004 Fuel is a liquid, liquids cannot be compressed, this is a LAW. When fuel has pressure, it is because the fuel pump has pumped in fuel to slightly expand the fuel lines and any other part of the fuel system that can expand. Well... yes and no. You're correct in the assertion that a liquid cannot be compressed (at least at the pressure's we're talking about) but liquids are compressable and pressure does build up in a liquid if force is applied to it. That's how boats float, that's why submarines implode when the pass crush depth, that's why Herion flows from the syringe into the arm, and its why a full liter bottle of Pepsi explodes so nicely when shot with a 30-06. If, theoretically, there was no part of the fuel system that could expand and the fuel system was full of fuel, there would be zero pressure (except that of gravity pulling the fuel towards the Earth). Not true. http://www.physlink.com/Education/AskExperts/ae15.cfm http://www.mpcfaculty.net/mbamate_rovcontest/canyon%20floor/activities/Pressure_in_the_Deep_Sea.pdf http://www.newton.dep.anl.gov/askasci/eng99/eng99234.htm http://www.askmehelpdesk.com/cgi-bin/yabb/YaBB.cgi?board=chemistry;action=display;num=1073282775 Quote Link to comment Share on other sites More sharing options...
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