Question about fuel pressure and BL numbers

[cottonpicker14]

Hi. my fuel pressure was set around 45 lbs on a stock TTA and my BL lean number was reading 151 at idle at operating temperature. I have changed all my hoses.
I dont have my own fuel pressure guage, but today I started the car, warmed it up and turned the screw in (clockwise) on the adjustable fuel regulator. I turned it about 2 full turns and as I turned it my BL number started to drop from 151 down to 137.
Since I dont know what my pressure is now, (will order a guage tomorrow) I was wondering that since I turned the screw inward I assume I am dropping the pressure.
Since the BL came down with lower fuel pressure, what would be the minimum pressure I should run (vacuum hose off) before its too low ? Seems my BL number is tied to a low fuel pressure but I dont want to have to little pressure and destroy the engine.
Thanks

 

[Jicaju]

Nope, your raising your fuel pressure.

 

[cottonpicker14]

So you are saying that by turning the screw in I am raising the pressure ? Ok, I thought that by turning it in, I would be decreasing the pressure since I was restricting the flow.
Any ideas where to get a fuel guage that mounts to the fuel rail ?

 

[TTA1326]

Hopefully one of the resident experts will check me on this, but here goes...


The BLM cells are a "learned" average of the fuel correction going on when your engine is running. A number higher than 128 indicates the ECM is adding fuel to compensate for a lean condition, and a number lower than 128 indicates the ECM is removing fuel to compensate for a rich condition. Factory calibrations keep the BLM numbers in the 110-150 range, but some aftermarket chips allow 90-160. In a perfect world you would like to see BLM values that don't deviate more than 10 points from 128, so 118-138. However, there are too many things that can cause deviations: weather, air leaks in the intake system, fouled O2 sensor, etc.

Now, the corrections are based off the calibrations in the chip. The chip is setup for the combination you have (injectors, turbo, etc), and it expects the base fuel pressure to be at a specific value (most of them are 43.5psi - 45 psi). So, if you change the base fuel pressure you may be making it worse as the ECM now has to correct the fuel for the initial problem (if there was one) and the newly introduced change in fuel pressure. Your changes in the BLM number might just be the weather, or they might be an indication of a problem (something like a pinhole in the factory spiral air hose from the MAF to the Turbo, etc).

I think you need to set the fuel pressure back to where it supposed to be for your particular chip and then determine if you have a problem before making any changes. Was the car running badly before you made the change?

 

[Razor]

TTA1326... AttaBoy

Hi BLM's is a lean condition sensed by the O2 sensor. And the computer is adding fuel to offset the condition. The higher the number... the more fuel its adding.

Start searching... I did a write up on T6P library section.

HTH