Finally going through the tuning process on my car, full build, 35r etc etc. The idle and cruise is fine, but when i go WOT it goes very lean. Tried making the map very rich, and still had a lean WOT condition.

Fuel setup- FULLBLOWN double pump (possible cause?)
-10 feed
-6 return
edlebrock FPR
AEM Fuel rail
FIC 2150
Relay to pumps

Boost leak tests were already done and good, its a speed density setup as well. Some say fullblown units can have this issue, but what are some causes and diagnostics i could to eliminate the possibilities?

Any help is appreciated! Thanks!

 

Do you have a fuel pressure gauge on the rail? I wish their was a way to remotely monitor the fuel rail pressure. I have seen the gauges under a cowl hood for fuel pressure, but that doesn't really work for our hood. You may be able to use one of the spare sensor channels and connect a pressure sender to data log it. I forget which channel you can use on the stock ECU, I think it's fuel temp or something along those lines. Or a stand-alone data logger could be an option also. Have you datalogged your Injector time (ms) or Injector duty cycle %?

 

Yeah there is a gauge on the fuel rail, set to 43.5psi. InDC and the time are good. As for using the fuel temp channel, I currently am using that for the speed density. Need to find a way to log the fuel pressure, but dot want to do more pulls with it going so lean..

 

Yeah, be careful with lean WOT. I just did a compression check and was low out of spec on #3 cylinder. Boo..

 

You can use the Rear O2 sensor channel if you are not using that one. The plug is under the passenger seat. I have my LC-1 output analog 0-5V to that for wideband logging. Easier than using the digital interface sometimes.

It takes some TephraMod v7 table changes to disable the ODB-II checks on the rear o2. I disabled them when I got my TurboXS turbo back, which free'd that channel.

 

What would I do to go about actually logging fuel psi? Sensor? Hookup? Wiring?

 

Yeah, it would probably all custom. First, get more fittings and Tee-off the pressure gauge. The 2nd line would thread into a fuel pressure sender. Finding one that accepts 5V and outputs 0-5V for a range of pressure would be ideal.

The sensor should have 3 connections

+5V
Signal output
Ground

You could expect a linear pressure/voltage plot which you would be like this for example.

0V = 0 Psi
1V = 25 Psi
2V = 50 Psi
3V = 75 Psi
4V = 100 Psi
5V = 125 Psi

Those are totally made up by the way, the sensor should have its ratings with it.

Now wire the sensor output up to the Rear o2 signal wire.
Also, the Rear O2 has to be disconnected. If the sensor is connected, it will affect the readings

In evoscan or similar, log the MUT ID for the Rear o2, but the formula would be like this.

X = 0 - 255 (which corrosponds to 0-5V)

Fuelpressure = (x/255)*(125psi)

Simple enough.

 

You might want to actually verify the sensor supply voltage, I am saying +5V from memory, the Factory Service Manual has the actual wiring tables and voltages in it.

 

Yeah easy enough, I'll have to give that a shot. What I'm still leaning more towards is a fullblown issue but not sure what the causes would be. What is a suggested gauge power wire from batt to relay, and relay to pumps?

 

Depends on the current draw from the pumps. I'd say 8-gauge would be plenty. The manufacturer should have directions/specifications that will give you the installation details.

8-gauge can safely transmit 24 amps. Here is a chart.
24 amps at 14.4 VDC is 345 watts.

Current capacity of a wire is not the only problem, if your fuel pump has a low resistance motor (most motors are relatively low resistance), and the wire is too small, the Ohms/1000 ft will be high enough that a voltage drop will occur before the pump, causing low pump discharge.

http://www.powerstream.com/Wire_Size.htm

 

Up for some more input.

 

I routinely log fuel pressure, but I don't think you need to do it. If you're running lean on a double-pumper with -10 AN supply and 2150s, then its its one of a few possibilities:

1) One of the fuel pumps isn't working.
2) The fuel filter is clogged.
3) The supply line has somehow kinked.
4) If one of the two pumps is on a hobbs switch, then maybe the switch has gone bad.

Not much else it could be.

 

Now that I think about it a little more, its also possible that the FPR isn't working properly (broken, or vacuum line leaking), or there could be a fuel leak in the hose between the pump outlet and the Full Blown housing.

 

Currently have 2 relays one for each pump, I had planned on a hobbs but went away with it, so I'm going to jump one relay, then the next to check if both pumps are working.

No kinked lines, and no leaks from the lines.

There could be the possibility of pump to housing leaking, so I'll try pulling the housing and check those lines.

Inline uel filter was checked prior to install and clean.

Its an edlebrock fpr, adjusted to 43.5psi. What's the best way to know if that's broken?

 

Watching the pressure at the rail can verify a few potential issues:

1) When the motor is shutdown, the fuel pressure should hold 43.5 psi for at least 15 minutes, if not 30+ minutes. Generally, what happens is that when the motor is shutdown, fuel pressure may initially drop to around 25-30 psi, but it tends to drift back up to the base fuel pressure, probably due the engine bay temperature causing expansion of the fuel. This will be more true on a warm day. After it reaches base pressure, fuel pressure should hold until the fuel cools off or until FPR or fuel pump check valve allow a bit of seepage. If that doesn't happen, then there's likely either an issue with the fpr not sealing or the hose sections between the pump and the pump housing are leaking.

2) Basic FPR performance can be examined simply by reving the motor while watching the fuel rail pressure. If the vacuum line is attached to the fpr, rail pressure should vary as the motor is reved. Also, disconnecting the vacuum line should cause the rail pressure to jump to 43.5 psi.