gpr

iTrader: (6)

I have a front mount turbo kit with a 7875 turbonetics and stock ls1 with head studs and cam. I originally had a new recetronic fuel pump and kit in the car so when i went turbo i added a second walbro 255lph pump.

I thought 2 255lph pumps would be enough, but when I get into boost (~4psi) I drop fuel pressure big time! Logged boost yesterday and I set fuel pressure as high as possible at 70psi then drops down to 30.

I'm realistically going to only make 600hp on e85 but would like a pump to support more so i'm not running on the ragged edge. Do you think something is wrong with the pumps? Should I add a third walbro 255?

Ryans99ls1

iTrader: (16)

I run 2 255's and make over 700wheel on E85. Something is up with your pumps/fuel system. FWIW i run a 58psi base pressure and 80lb injectors with -8an feed and -6an return

HRHohio

Did you add the correct 255lph walbro? There are "low Pressure" and a High Pressure versions I believe.

What model 255 did you get? (P/N, etc). Where did you get it from?

I ask this because I bought a BBK 255 fuel pump from a friend when mine went bad. Turns out it didn't like boost. Ended up getting a Walbro 450 on Ebay instead.

Here's an interesting thread:
http://contour.org/ceg-vb/showthread...low-vs-HP-data

skinnies

iTrader: (33)

Two 255's will support right at 800rwhp before they run out, done it many times. I recommend a 3rd pump after 750rwhp.

gpr

iTrader: (6)

I got the walbro from show me speed. Was going to buy one of their double pumper kits but since i already had the racetronix pump he just sent me one pump with the rest of the parts for the kit.

I have the walbro and the racetronix (which is a walbro pump) both mounted in bucket going to a tee then it goes directly to the outlet of the fuel pump housing. I removed the in tank regulator. I have factor lines to the factory rails, and a boost reference regulator connected to the shradder valve of the fuel lines, then it returns back to the tank in the evap line. I did it this way as i saw several other people running stock lines with no issues at big hp levels.

The odd thing I don't understand is how I can hold 70psi while driving, then once in boost it drops to 30??? I will pull the tank and check it out. Maybe only one pump is working?

One thing is the racetronix pump has that extra port that comes off it and goes to a small line, which in a factory bucket is just used to keep the bucket full of gas. Would this be hurting me when running dual pumps?

smokeshow

iTrader: (17)

Try setting your base fuel pressure lower instead of higher... Give it a shot around 45psi. Make sure any necessary changes are made in the tune to account for the different fuel pressure.

DropShipDave

I'd def check and see if the other pump is working. I'm planning on running dual 340's for my car. Planning on ~800whp on e85 when its all said and done.

gpr

iTrader: (6)

I had the fuel pressure set at 45psi and then 58psi at one time and both were running lean in boost. (I'd assume the fuel pressure was dropping then too but didn't have a gauge hooked up.) So i cranked it up as high as possible to see if it would still go lean.

turbo6man

iTrader: (5)

Is your regulator a 1:1 boost referenced. If so as the boost increases it squeezes off the return which should increase the fuel pressure by 1 pound per pound of boost. This makes the pumps work harder. if your pumps are not up to snuff the pressure will fall. If your having this type of problem the pressure drop gets worse if you increase base pressure. Also a bad ground or low voltage to the pump will also make them not perform as they should. I just went thru a crazy problem with my fuel pressure dropping. This probably does not relate to you, but I had a problem where my 140 amp alternator had a diode Bad in the rectifier circuit. It would charge fine up to about 50 amps then it would quit charging all together. So driving around everything looked good but under boost when the electrical load was greater than 50 amps it would quit charging and go to battery voltage. I data log fuel pressure and I can tell you my pump puts out a lot more at 13.7 volts than it does at 12.2 volts. To make matters worse (this was a totally different issue)when I checked voltage at the pump it would loose just over a volt from what battery voltage was. I replaced my fuel pump relay with the recommended one from Magnafuel and that cured my voltage drop from the battery to the pump. Good luck and I hope you get it figured out.

turbo6man

iTrader: (5)

I also remember when I first switched to E85 I had the aeromotive fuel filter which was the fiber type installed. I started to have a fuel pressure drop. I removed that filter and put in the recommended stainless steel mesh one and the problem went away.

On a side note when I removed the original filter I could barely blow thru it. I left it off and let it dry while I ordered the stainless one. For some reason I blew thru it again when it was dry and it blew thru fine??????

HexenLord

Unhook your boost reference on your regulator. Run it at 58 PSI static for a few PSI of boost and see what happens. Worst case scenario, the same thing happens.

Also, do both of the pumps have internal check valves?

gpr

iTrader: (6)

These are some good ideas i will try in the morning. the fuel filter i think is stock... Where do you get a stainless mess one? i might remove it and puncture it so it is straight through then reinstall and try it again to make sure the filter isn't the issue.

and yes the regulator is a boost reference 1:1 regulator installed after the rails. I will put it back to 58psi and modify the tune for it and try that as well.

69Tinindian

Are your pumps Y'd or in a series in line?...I had to y mine I was out of fuel at 600hp

turbo6man

iTrader: (5)

I have an aftermarket Aeromotive filter and I just screwed it apart and installed the stainless one. When was the last time the filter was replaced? You should be able to remove it and blow thru it right away. If it is plugged you will know it. A good filter is usually alittle hard to blow while it is filled with fuel, but once you blow that out it blows pretty darn easy. A bad filter will be hard to blow thru even after the fuel is out of it. Best of luck

gpr

iTrader: (6)

I pulled the fuel filter and blew threw it. Blows through very easily and does not seem to be anyway restrictive even when it was full of fuel.

I changed the fuel pressure to 58psi, and in doing so i think possibly my regulator is not working correctly. To set pressure i pull the vacuum line off and turned the screw till it was right at 58~59psi. I then stuck the line back on and it dropped to about 45psi at idle. I pulled the vacuum line off again and fuel pressure really didn't change any. I would think it would go back to 58psi?

So i started turning pressure up again and it suddenly shot up into the high 60's. so seems as if my regulator might be bad.

Also i noticed as i drove it this morning that at different vacuum levels the fuel pressure was different. As i was driving at different throttle positions and rpms, that at 7.0 psi of vaccum no matter what should have same fuel pressure?

gpr

iTrader: (6)

One more question on how a boost reference regulator should work. If I pull the hose and set the fuel pressure to 58psi, once I start building boost (so 0 boost but 0 vacuum) I should be back at 58psi, correct?

Then as i get into boost at 1psi boost i should be at 59psi, at 5psi boost i should be at 63psi fuel pressure etc... correct?

gpr

iTrader: (6)

Ok, i went and ran the car again unplugged the vaccum port on the regulator so it was a constant fuel pressure. I was still loosing pressure once i get into boost.

Here is a screen shot of the log, but by doing this i'm thinking there has to be something wrong with the fuel pump. It is almost like only one pump is working. Also note that at 14.3 psi on the map sensor is about 2psi boost at my elevation.

HexenLord

Odd.

The reason I wanted you to run the regulator without the line hooked up to it was to see if the rate of gain was incorrect or if the line was hooked up incorrectly. With no line attached to the regulator you should have maintained a constant 58 PSI even when you went into boost. You SHOULD put a check valve on that fuel pressure regulator line. You dont want the regulator seeing vacuum, only boost pressure. With an open line, the regulator sees vacuum which pulls the fuel pressure down.

Look at your log between frames 2600 and 2700. You start building boost around the 2600 mark, and your fuel pressure comes down at almost the exact same rate. The lines for fuel pressure and boost pressure between these frames looks like a mirror image. You were only at about 3000 RPM here when your fuel pressure started to drop, so you definitely weren't running out of pump.

Was your vacuum line to the regulator hooked up during this run? Your fuel pressure shouldn't tank like that at 4 PSI or less, even if only one pump is running. How do you have your pumps setup? Are they running parallel or in series?

And yes you have it right with the boost/pressure gains on the regulator. You should never go below 58 PSI, and pressure should go up 1 PSI for each PSI of boost assuming you have a regulator with the correct 1:1 rate of pressure gain.

gpr

iTrader: (6)

The screen shot i posted was taken with the vacuum line disconnected from the regulator. The fuel pressure remain constant at 58psi all the time except when I got on it, and you can see it drop. Thus why I was thinking the pumps aren't supplying enough fuel.

Maybe the regulator isn't good? (it is an old one I had laying around and ran it on a supercharge grand prix back in the day) Because if i pull the vacuum line from the regulator and set the pressure when I reinstall the vacuum line to the regulator then fuel pressure drops. This isn't suppose to happen?

My setup is as follows: I have a racetronix 255lhp and a walbro 255 pump both in the factory bucket. I have them tee'd together into the output of the fuel bucket. (btw, I currently have both pumps wired to run all the time) This runs into the factory fuel line up to the rails. (i have the tee in the factory line back by the tank remove so it can't return to the tank) Then off the front drivers side factory fuel rails I have a line that runs into my fuel regulator, then a line out of the regulator into the evap line. At the back i have the evap line connected into the return on the fuel bucket.

HexenLord

If the regulator will hold 58 before going into boost, then its probably not a bad regulator, especially since this is happening with no vacuum line hooked up.

Also, you want a check valve on that vacuum line, you don't want the regulator seeing vacuum, only boost. its much easier and safer to tune for a narrow sweep of fuel pressure than a wide one.

Also, are there check valves on those pumps, and are both of them rated for high pressure? Its possible that one is back flowing through the other. Also, are you data logging fuel pump voltages during these runs?

You're going to have to go through a process of elimination. Like swapping in a different fuel filter or doing a run without it, and checking voltages on both pumps