in Tunerpro. Is that where I put in my size injectors?
I'm using 8 that are LT4 style, 28lb/hr. Presently the number in there is 56.05. Just making sure its correct. thanks

 

That sets the injector flow rate for the WUD's trip display.

The injector flow rate for the fueling calculations in the ECM is set by the BPC vs VAC table entries.

RBob.

 

So there is no place to put in my size injectors in the constants? From what your saying all fueling is based off the BPC-Port worksheet. If thats incorrect then the whole fueling table is off. Which could explain my "lean" problem.

Spoke with Jon at Ficinjectors and he told me that my injectors are not actually 28 lb/hr and that GM advertised those for the LT4 but actually used a injector that flowed 25.7 lb/hr. So I reset my BPC to 160. At first it acted better but after a couple of BLM VE's it started to run lean again.

Also used a couple of worksheets online and based on 350hp at the crank I should be using a injector rated at 31lbs/hr. But can't find a conversion to see what FP I can run to compensate for the differance.

Wondering now if I should be running my FP closer to 50psi. If anyone knows this conversion please let me know.
thanks

 

The BPC (base pulse constant) is the engine displacement term and injector flow rate term rolled into one value (or table of values based on manifold vacuum). For a port injected engine all BPC table entries will be the same.

Setting those table entries takes care of both the engine displacement and the fuel injector flow rate for the PW calculations. Acceleration enrichment (AE) fuel PW are handled separately as there own set of PW calculations.

The INJ - MPG (mile per gallon) injector flow constant is for the WUD's trip calculations. This constant is not used in the ECM at all. It is in the calibration to be forwarded to the WUD for it's calculation of fuel consumption.

To calculate the required fuel requirement and/or the required increase in fuel pressure for this requirement, can use the BPC-Port SS. On the right side of the SS it displays the approximate HP that can be supported by the current entries. This is at .45 BSFC and 85% duty cycle.

Just change the fuel pressure until the HP number is what you want.

The injector flow rate can be calculated as: NewFlow = SqRt(NewPsi / OldPsi) * OldFlow

If the O2 feedback in closed loop is causing the engine to run lean, then there is a different issue then the injector flow rating. Look to see what the BLMs are doing. That will tell you what the O2 sensor feedback is telling the ECM.

It may be something as simple as a silicon poisoned O2 sensor.

RBob.

 

Think I understand what your saying.
So I think I'm making progress but need to check with you.

Reset my Fuel pressure to a Static Pressure of 50psi
When the car is running my Fuel Pressure is 42-44 psi
Set my BPC-BPC vs Vac to 151 ( got this using the BPC-Port ss , 25.7 lb/hr for injectors and 50psi )

At cold idle my WB02 was 12-14
Once warmed up in Closed loop WB02 range was 14-16. Ran the car up to 2500 RPM. It does seem to have improved my A/F

Should my Fuel Pressure be set higher while the car is running?
Or do I use my Static Pressure for the BPC calcuation.

Think I'm getting close just need to pick your brain a little more.
thanks

 

On a port injected engine the fuel pressure should be set with the vacuum line off (static pressure). This is the value to use in the flow rate or BPC calculations.

With the discharge end of the injector exposed to manifold vacuum, a VRFPR is used to maintain the same fuel flow rating throughout the manifold vacuum range. That is the differential pressure between the injector inlet and the output remains the same. As such, so does the injector flow rate.

The newer vehicles that run a constant pressure system with no return line have an injector flow rate table vs vacuum. Similar to the EBL when used with TBI and a VRFPR. Which is why that table exists in the EBL.

RBob.

P.S. need to change your sigs to HSR

 

Sig is changed... thanks for the reminder.

Think I'm making progress on this. Set FP to 43 (running) BPC is at 165. Seems to act a little better. WB alarm in software is still going off quite a bit.
I was able to start my BLM VE learns today on the road. Put about 10miles on it at this point.
thanks for your help.... again!