Hello all. I had a difficult time getting 80# injectors to idle decent using E85. I decided to run a return style system to lower the idle fuel pressure making less pressure on the injectors and getting it to idle smooth. I was unhappy with the results by changing the injector settings alone to get the injector pulse width small enough for a nice idle. With a bigger injector the ECU's injector driver struggles to fire the injector fast enough which ends up making the car idle choppy and usually rich.... To do this you will also need a way to modify the ECU such as HPTuners. The car runs great and idles perfect now. I am VERY HAPPY with the results. Some people can get bigger injectors to have a tolerable idle but I think a return style system is a better route. *** DISCLAIMER*** this is how I built my system. I am not responsible if attempt this and have bad results or blow something up.
Here's my parts list.
I decided to go with -6AN for the hose and fitting size. Its close to the 3/8" size of the fuel feed.
Misc Items: Zip ties and vacuum T
Hardware from Summit Racing:
AER-FBM2872 STEEL 3/8 BRAZE/#6 FLARE - $5.95 (1)
SUM-220166B -6 O-RING TO -6 FLARE FIT BLK - $6.95 (2)
SUM-220631B -6 PLUG O-RING BLK - $1.95 (1)
SUM-220637 -06 BULKHEAD UNION - $3.95 (1)
SUM-220687B -6 90 DEGREE BLACK HOSE END - $11.95 (3)
SUM-220690B -6 STRAIGHT BLACK HOSE END - $3.95 (1)
Hose from an Ebay Store:
-6 AN Braided Stainless Steel Fuel Line Hose 1500 PSI | eBay
You will need about 12 to 13 foot. Depending on where you want to mount the regulator.
Fuel pressure gauge from an Ebay Store:
Marshall 0-100 PSI Fuel Pressure Gauge 1.5 Black 15029 | eBay
Adjustable fuel pressure regulator from an Amazon store:
I went with the Aeromotive compact EFI regulator to save space. You can pretty much use any regulator with a boost reference port. I'd recommend getting a good name brand one.
You may also want to get a higher volume fuel pump while you are at it. I did not since mine was able to keep up with the demand of my setup.
You may also want to get a inline fuel filter since you cannot use the one in the tank. I got a mesh screen one from the auto parts store. Its part # is F29160 - Purolator. 2 high pressure hose clamps or ear clamps are needed too.
Another thing you may want to get is a LSJ fuel rail from an ION redline or Chevy colbalt since it is easier to modify to a return system.
Once you have all the stuff you need...
Step 1: Remove the trunk liner. It pretty much just sits in there. Dont forget to remove the convertible top drain tubes, elastic cords on the side and unplug the trunk light. If you are unfamiliar with dissembling the trunk you can look at the free shop manuals on line using Autozone's website. Put the liner in a safe location like a boat.
Step 2: Remove the metal access cover. Take out the 7mm screws and pry up gently with a screwdriver. This will give you access to the pump housing and the top of the fuel tank.
Step 3: Disconnect the fuel hoses and connectors. You may want to relieve the fuel pressure via the schrader valve on the fuel rail. No special tools need for hose removal. Most just push on the tab and pull off. The big hose next to the fuel line probably wont move enough to be fully disconnected. Just loosen it up for right now.
Step 4: Remove outer fuel tank ring. This is a challenging part. It took a little bit of time for me to get this sucker to move. I have seen people use an air chisel but, that didn't work for me so I use a prybar and hammered the tabs counterclockwise.
Step 5: Pull up slightly and back to the rear left side of the car. This should give you enough room to get that hose off. Once the hose is off then pull up but make sure you do not damage the fuel gauge float. At this time also you may want to drain the gas out of the sending unit by tipping it slightly to the side.
Step 6: Disconnect the 2 fuel hoses off the metal in tank filter. As you can see the pump sits in the center of this goofy filter. The stock fuel pressure regulator is also part of the filter so that will need to be removed. You can remove the stock filter and regulator or keep it in place. I decided to just keep it in there to make sure everything stays in place. This would also be the time to remove the stock pump if you are upgrading it.
Step 7: Bulkhead installation. Find the center of sending unit. There is enough room for the bulk head and the nut to fit. Make sure you check the bottom side of the lid so you do not drill into anything and you allow enough room for the bottom nut. I used a 1/2 " drill bit and threaded the bulk head into the plastic, then I secured the bottom side with a nut. You may also want to add an O-ring or some kind of thread sealer at this point. Remember, no hose or anything extra is needed to connect to the bottom side of this bulkhead since fuel is just getting dumped back into the tank.