JasonCzerak

My main problem is running out of fuel at 1/2 tank and fuel gauge reading 0/empty.

Recently I've done an e85 conversion and upgraded my ECS stage 1 pump to an A&A twin pump (using the ECS supply/return block already installed on the tank) and Holley rails (bumped injectors from 60# to 80# as well).

Fairly straight forward install (oem feed line/pump for normal driving) retaining the in tank regulator and the Holley external regulator. We shouldn't need to be beyond 58-62psi (actual psi) in the rail to obtain WHP goals under boost ( effective 48-50). I have the boost/vac line hooked up to the regulator per the tuner request.

I also removed the evap line that runs from tank to throttle body. The tuner didn't want any extra vapors messing with A/F. One thing to note is that I did "cap the line" at the firewall until lastnight.

I'm fairly sure i'm not missing anything else relevant, but ask away!

I've done some minimal research around how the transfer works so i'm not completely sure how some of the physics works in my situation. I understand the passenger side tank empties first then the drivers side and i understand this to be a venturi effect type of process. there's also a Y in the lines with some check valves as well as a regulator in the passenger tank. There are some flow specs, but i'm not going to be able to test them since i'm not dropping the tanks any time soon.

• Would blocking off the evap thing at the motor cause pressure differentials to mess with the tanks ability to transfer fuel?
• If my seconday regulator is set to say, 40 or 50psi at idle motor running under vacum, is there enough pressure at the intank plumbing to create a flow diversion into that Y in the tank to effectively move fuel from the passenger side to drivers side?
• Chances of e85 breaking up crud in a 32,000 mile old 2006 car clogging that fuel transfer stuff?

JasonCzerak

Well, not sure how I didn't run across this before

http://www.lingenfelter.com/mm5/merc...3#.Vf21-d9Viko

schpenxel

Basically as long as your fuel pressure is near stock (at the minimum point), then you don't have to replace the passenger tank bypass valve thing. If you get down somewhere in the low to mid 50's, the bypass valve in the passenger tank closes, effectively disabling the system that transfer fuel from the passenger to driver tank.

The logic is that if fuel pressure is too low (relative to what GM designed it to have..), then don't waste what you do have on moving fuel around.. I would think this would only happen on a stock or near stock setup for a few seconds at a time near red line @ WOT on a totally stock fuel system.

I'd try bumping the pressure up to 60psi or so and seeing what happens. Actual PSI, not effective.

You really need to block off the driver side built in regulator if you want the regulator you've added to actually do much.

tblu92

Are you sure both sides of the tanks are vented properly ? and isn't there a transfer pump between the 2 sides ??-

JasonCzerak

Unless something recently clogged things up, all venting is untouched with exception of removing the motor side stuff and leaving the front to back tube wide open.

schpenxel

There isn't a separate pump.. it uses pressure from the fuel pump to power a system that moves fuel from passenger to driver tank.

Here's more than you've ever wanted to know about how it works:

http://www.corvetteactioncenter.com/...ystem-389.html

JasonCzerak

So I settled on the fact that only fuel from the drivers tank will be used until we over-ride the passenger tank venturi pump (thinking, -12 lines at the bottom of each tank and let gravity transfer).

Today was interesting again. Based on miles driven and MPG average that I should be getting (about 20-22 with stop and go and higher speed highway) and a total of 50 miles driven I should of consumed 2.5 gallons.

Well, the fuel gauge was moving rather fast by the time I got to near my destination the fuel guage worked it's way to just past a 1/4 tank... weird, should of been about 1/8. Then the gauge went to zero! Pulled over and checked the fuel pressure, spot on at 50 (yes, lower then 58, but there's a reason for this). So I got fuel. Car's driving fine.

Decided to drive to the Holiday and top off on e85, 1.3 gallons and the nozzle clicks off. I'm just over a gallon short of what I needed to put in the tank?..

Unless for some reason I was actually getting 38MPG with e85 this isn't right.

I'm thinking the venting is broken now.

JasonCzerak

Another though after looking at the link schpenxel provided, I wonder if the FLVV was what was blocking my expected extra gallon. Considering the venurri pump isn't working perfectly as expected, I could of very well not consumed enough fuel to properly fill the expected amount.

schpenxel

I was about to say the same.. sounds like the passenger tank is still full, meaning the fill vent is closed.. which will make it tough to get more fuel in the tank since air is trapped

JasonCzerak

So, even with only a few gallons used, the fuel level thing isn't working all that correctly..

What do you think about adding a -12 line between both tanks at the bottom to facilitate a fuel transfer? as apposed to dropping the tanks to cap off the internal regulator(s)?

I wonder if I do this, I could disable/unplug the internal pump, cap off the OEM fuel line and run one of the Holley pumps (A&A kit) full time.

schpenxel

Can you not just bump the fuel pressure up? At the very least temporarily to make sure that's the issue?

JasonCzerak

I'm considering that, but the tune gets upset with more fuel then expected.

schpenxel

Put it in closed loop and let fuel trims do their job

(and bump 10% out of MAF/VE tables, it'll be fine)

JasonCzerak

Just a brief update on this. There wasn't and hopefully won't be a need to drop the trans out of the car any time soon, thus blocking the internal regulator wasn't happening

We did end up connecting the two tanks with a -8 line. On the right side we tapped into the plastic, on the left we T-ed into the ECS bulkhead fitting's supply -8 that was going to the secondary pumps. The idea here is that when the secondary pumps kick on under boost, it draws from both tanks, plus an additional hole wasn't needed in the left tank. When under normal driving, the -8 line will use gravity to balance/transfer the fuel.

I may have that right side tap replaced with an ECS bulkhead fitting, since this one drips every now and again ( argh ). It really is a nice fitting.

The end result was a perfect success! The fuel gauge works properly all the way down to 1/16th of a tank. No funky check engine codes. Even under brief acceleration while < 1/4 tank it doesn't appear to be staving the motor (A/F stayed where it needed to). I'm very happy to have nearly 200 mile range on e-85 on a tune that hasn't focused on any sort of MPG yet.

The down side to this hack is the internal regulator is still in play. So with just the A&A twin pump installed max fuel pressure will not exceed 58psi by much since the fuel will end up getting pushed back down the OEM feed.

In my case, the tuner, KLTunes wanted to work with 50psi of idle vacuum/boost referenced to 58. It was a good compromise and worked out will (805whp is the current power level).

This coming spring I'm going to re-work the fuel lines under the hood a little. I need to upgrade to ID1000's so I'm going to re-do the A&A lines as well as my lines to the holley rails.

Apparently you can get a one way AN fitting with a check-ball valve for a -6 line. I plan it put this checkball on the OEM feed, effectively disabling the internal regulator during conditions when the secondary pumps are active, allowing for >58psi of fuel rail pressure.

Another upgrade will be flex-fuel sensor and Ethanol % gauge plumbed into the return line. I've decided I'm not going to deal with testing fuel at the pumps constantly to guess what exactly is in my tank at the moment.

JasonCzerak

realcanuk

I'm not sure I would be comfortable with that crossover being so low and also so near the exhaust.

I have a very similar setup to your fuel system and have also not dropped the tanks to do the block offs, because is don't feel like dropping the tanks. I run it at a base of 58 psi, and everything works as it should. Main difference is I am not on E85 but I don't see that should make a difference.

JasonCzerak

After 1500-ish miles or so we put the car on the lift and inspected, everything seemed just fine. No melting, no movement. we'll see what happens on longer trips and hotter days, but these are the same tubes for the oil cooler and other various things on the car.

brodyscorvette

If you add a check valve to the discharge side of your external pump and another one to the factory feed line (before they 'Y' together) would the factory feed be able to supply flow to the total flow at >58psi rail pressure?

JasonCzerak

The external pump (A&A kit) already has a check valve, the only check valve I'd be adding is in the factory feed.

i'm no fluid dynamics expert here, but due to the regulator in tank, the factory feed line will never see anything beyond 58psi until it's capped. Considering the dual pumps as a pair are much more powerful than the factory pump it's actually pushing fuel back down the factory feed past the factory regulator; that's what I'm intended on stopping with the check valve in the factory line at the motor. The entire motor will be running on fuel supplied from the A&A pumps at WOT with the ability to tune that pressure beyond 58psi, once the check valve is in place.

If you were to block the in tank regulator, I'm sure all 3 pumps would work together (with out a check valve in the feed)

Proud Owner

After running E85 for the past 8 years I am NOT going to run it in this Vette. The HP/TQ gain is not worth it to me anymore. Burning 30% more, fuel pumps,fuel lines,surge tanks,running lean,road trips,locating a station, finding a tuner that really knows E85 is not easy (ghost knock), the extra expense of the mods necessary to run this stuff. I know it sounds like a rant and it is.