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After kicking around many ideas I decided to go with an external surge tank and external pumps to feed the fuel rail of my rb25det in my 240z. I tried an intank fuel pump previously. The intank pump is the way to go for sure as long as you have adequate baffling and good general design. My problem stemmed from a poor design and using a rusty tank a buddy gave me. I started a thread on that. http://forums.hybridz.org/topic/94261-bonks-efi-fuel-tank/ I will update that thread with some lessons learned soon. Luckily I still had the original tank I pulled out of the car at the start of my project. It had a little rust, the local radiator shop was able to clean it out using acid and hot tanked it ($89). The key to my project is that there are no modifications to the stock tank. I chose to use the bcbroncos product, Accumulator Tank, ( http://www.bcbroncos.com/fuelefi.html ) scroll to the bottom the page. The tank is a converted remote oil filter. The guys at bcbroncos use this tank for their EFI conversions (if the customer does not want to spring for the intank solution). Fuel goes in the top, pass through the filter, there is a pickup tube that extends to the bottom of the filter where the fuel is picked up by the HP pump. bcbroncos added a third fitting (5/16ths) to the top of the modified oil filter to manage the return system (see tee fitting in website image). You plumb the return from the engine to one side of the tee and the return to the tank to the other side. I am feeding the surge tank with a low pressure Airtex 8016S pump. On the engine side of the surge tank is a high pressure Walbro GSL392 pump. The obvious problems with this kind of are the following: 1) Mounting everything (there aint much room) while staying away from the exhaust and the suspension and anything else that moves (rips). 2) Return Pressure Part A - there must be free flow from the fuel pressure regulator (FPR) to the tank. If the system lacks enough return capacity (adequate fuel line inside diameter), pressure can build up in the surge tank. In this case that is not an option because the tank is nothing more than a thread on filter. People have reported problems with their bcbroncos accumulator tanks leaking. I suspect that is because they did not have adequate return capacity to the tank and pressure built up inside the surge tank. 3) Return Pressure Part B* - if there is not free flow after the FPR then the HP pump has to work under load and will get HOT! = BAD for pump and WIRE! If the HP pump is working hard and getting hot then the WIRE feeding it juice is getting HOT. 4) Noise of external pumps (live with it) * - source Tony D. 1) After looking around the back of the car for a while I found a cluster of three threaded holes. I made a plate (1/8-inch) and threaded M6 hardware into the holes. I use the plate as a base to weld an extension out of some small box tubing. This was needed to move everything away from the Mustache Bar. I welded another plate to the box tubing, drilled to accept the surge tank and pump mounting plate (16-gage sheet metal). 2) After exchanging emails with Tony D, I was convinced that I needed to increase my return capacity to the tank. I already replaced the little pinner 3/16ths return line with 5/16ths when the drivetrain was out. But the stock tank has that 3/16ths return above the 5/16ths pickup. I decided to swap my usage of the 3/16ths return line with the smaller top of tank vent line (@ 5/16ths or a little bigger. At this point you simply need to make a 3 to 5/16ths adapter to plump the stock return to the vent tank. 3) After doing some research on the amp draw of the pumps and exchanging emails with Yury at Wiringspecialties.com we decided that I would be OK running both pumps over the stock 10-guage wire that runs from the back of the car near the tank (Nissan ran it back there to allow for an optional electric fuel pump on the carburated cars) to the front (Green wire). I am monitoring the wire (grabbing it to see if it gets hot) as I've running the cat over the last few weeks and have felt to heat at all. The Walbro has never gotten hot at all. The LP pump gets warmish, but not hot. 4) The Airtex pump makes a lot of noise (grumble) at idle. Can't hear it when you are underway. It doesn't bother me. Priming the system, I disconnected the power and ground to the Walbro and cycled the car in the ON position running the LP pump. I waited until I heard gas falling from the vent fitting back into the tank. I connected the HP pump back up and went for it. Damn thing started right up. Crazy. The Bad/weird part. When I shut the car off the LP pump continues to run for a second or two. I have a an inline fuel pressure gage in the engine bay. After I turn the car off it reads @ 25 psi pre-rail. After 20 minutes or so the pressure bleeds off. I am concerned this may not be good for the FPR. BUT the remnant pressure is great for one thing, starting the car back up. When I had my intank setup. I had to prime the system in the ON position everytime I started the car. Now, no need, the fires right up on the the first crank everytime. Thanks for reading. Bonk
