I have noticed that actual injector flow tests (such as in the web link below) and the injector constant in the stock .bin doesn't match up with reality.

http://dtcc.cz28.com/flow/index.htm
(The data in the university test is fairly consistant with data I've seen in other tests and flow charts)

For example, in the arap, aryp, apyn etc .bin's for $6E, the injector constant is 22.38# @ 40 PSI. That would adjust to 23.3# @ 43.5 PSI.
The flow rate for the stock injector in the above flow test produced 21.6# @ 43.5 PSI. That adjusts to 20.71# @ 40 PSI. So, it appears that GM over-reported the real flow rate by about 1.76# (22.38-20.71)

Which brings me to my delima. Should I set the injector constant in the .bin to the ACTUAL flow rate for the PRESSURE I intend to run, adjusted to "40" PSI as stated in the .bin?

Granted, I realize that the injector constant may change during the tuning process, but wouldn't I want to start from the true value at the pressure I intend to run? And why would GM understate the injector size in the first place? Were they intentionally running it lean or is something wrong with my logic here?

 

Good question!

I hadn't realized before that in $6E the bin shows that the fuel injector constant calls out for a 40 PSI value.

 

I always set my injector constant in the prom to the actual flow rate of the injector at the pressure I am running, not advertised flow of the injector. Then I make all fueling adjustments in my prom. So I would say you are correct in your logic, although I can't explain what GM was doing with their settings.

 

I agree that you should set your injector constant in the prom to the actual flow rate of the injector at the pressure you are going to run BUT the actual flow rate will probably be in a range. In my case I am running 24lb Ford SVO's to support about 410-420 flywheel HP so I am running 50 psi to ensure enough head room at 6,000-6,200 rpms. The dilema I had was the same - whats the real flow. I found for my combo the Fords probably flowed more than 24 lbs at 43.5 psi and when I adjusted to 50 psi and set them at 25.? as I can't recall now, they were rich across the board. I now run them at 26.78 on the chip and the only MAF adjusts I had to make were in the first two cells and my BLM's are in the 129-130 range under all conditions and even without a wide band I feel safe that my O2 is over 875mv at any point in PE at all rpms and is mostly over 900 mv which is the best I can guess at with out a wide band. Plugs are also reading good with my limited knowledge.

 

Has your MAF been modified as in no screens or fins?

 

Rear screen removed - 20% of front strands removed - fins left alone.