injector flow rate tables

After playing around with my tun I realize that tuning a pcm always are compromises between theory and practical experience. There are so many unknown factors in those operating systems that the easy theory seldom works out.
I am working on a 12212156 os that I am using on a stock ls3 engine. The engine runs and it has run a few hundreds kilometers this summer.
I started with a self made mix of ve tables and have used calc ve tuning and wideband to correct this table. The result is that more tuning and correcting, les sane values in the ve table. Obviously something is wrong. I have not trusted the wideband readings and now I have two new nb sensors and one new wideband sensor to be installed. Even then I don’t think this is the problem.
I also have a new used 411 pcm in the post somewhere. I need to eliminate every possible fault factors.
To build a correct ve table I feel that I need to start with correct injector flow data. I thought this was the easy part but not. The stock ls3 injector have bean used for several years with several application. I have got some tables from jocar and some other posted on the forum. First I thought that the ls3 had new injectors in 2010, and used some data from 2010 camaro because this was higher. The ve table upper part got fine but a bit to high. The lower part was way too high. Then I used the corvette values from jocar and that values gave to low readings in the upper portion and retained the same values in the lower part. My practical experience tells me that something is preventing the injector from give short enough opening time. Or less enough fuel. I have found a cax file for table b9021 and am going to test it.

The flow rates on the injectors are corrected by b3701 pulse width voltage adjustment. On the small ls1 injector this is about 0,4 ms at 14v. On the large ls3 injector this is about 0,7ms. This is a lot of fuel added on this big injector. How is this table handled in conjunction with the b4001 injector flow rate table? Is this correction also added to small pulse, (more then one pulse each stroke)?
When testing injectors. Are they stuck open for a longer period of time and the amount of fuel measured? And is this why we need a correction in b3701 at 14v, to imitate a duty cycle? Or are the injectors tested at different duty cycles and the B4001 average corrected for opening and closing time?
Can somebody please explain how this fuel injector tables in the 12212156 work together to give correct fuel flow numbers?

Hi Tor,

This is how we believe the PCM calculates IBPW: showthread.php?13364-IBPW-B4005-B3701-correlation

Also see post #27: showthread.php?10179-Injector-Base-Pulsewidth


Injectors are flow tested by running static open (100% duty cycle) at something like 12V.

At other voltages, the injectors respond differently (quicker as voltage increases), so B3701 is required.

The difference between the commanded open time and the actual open time is referred to as the injector offset; this is what the various injector characteristic tables are modeling.

Hi joecar

Thanks for the very informative links. I have changed back to recommended injector date from 2008 ls3 corvette, and are doing auto ve with wideband and maf disconnected. The ve table takes form, but I need more full throttle date, and need to understand what happens in the two lower 15 and 20 maf part of the ve table before I am satisfied.
I wonder what in the tune that adjusts the air that’s entering the engine on deceleration? I have a feeling that the IAC let to much air in to the engine when letting of the throttle and slightly reducing speed. Is this the iac park position? Throttle cracker? Or is it some other tables?

Good question... possibly the throttle cracker (by way if IAC) may be allowing air thru... but the PCM recognizes this as being deceleration mode... so I'm not sure what the PCM does with the IAC/cracker.

Post some logs including IAC, STATE05 and some airflow pids.

When thinking thru ought this deceleration situation I realized that when I built the tun I used a mix of tables from ls3 Corvette Camaro 2002 and ls6 zo6. Most of the idle stuff was from z06 because the cam data is closer to the ls3. The ls6 use a drive by wire throttle body. I use a cable driven NW 92 mm with 2000 Camaro IAC. The throttle cracker data on zo6 and the Camaro is very different.
As a test I copied over the throttle cracker and throttle follower data from a stock 2002 Camaro. Then I logged, first the pids for auto ve and then some iac pids on the same trip.
Under the test drive I realized that the deceleration was better with no bugging or stumbling. Still I would like some more engine braking, but it is quite like stock.
When looking at the auto ve log I se that the data have changed a lot in the lower then 1200 rpm range. It seams like the altered settings in the throttle cracker and follower have influence on the ve table. Another change is that my natural idle speed now is to high (650) or so. I am attaching the two logs, and the auto ve tun of today.
I would Appreciate any comments on this subject, or on the tun it selves.

The IAC Airflow tables (Desired Airflow, TC, & TF) only have a tangential influence on fueling. If you log IBPW1 and MAF Frequency (or VE Table Look-Up), you will not see any change in those parameters when you change the IAC Airflow. What does happen though, is by adding/subtracting air..you inadvertently change the RPM/MAP rate of change. I.E., if you 'hang' the idle, the RPM & MAP will also hang. But the IBPW1 and MAF frequency do not change. So if fueling is affected, it is in essence 'back-dooring' it.

Which proves Desired Airflow, TC & TF need a lot of work to get a perfect balance between normal deceleration and dropping to slow or too fast.

My only advice is not drive around with too much air in the TC. It really comes into effect when you take the foot off the throttle. Too much air will hang you up. The TF is mainly used when your foot is on throttle. As long as your decay rates are fast enough, you can usually go as much as 400-500% higher on TF airflow. It almost seems to act as an 'accelerator pump'. With enough TF when you hit the throttle it really opens up. I use the TF RPM Multipliers as indicated in the Idle Tutorial..http://forum.efilive.com/showthread....ul-Info-Inside

I use the TC from a 1998 Camaro Automatic and then fine-tune it. Much less air than stock M6, but enough to give some throttle response..http://www.holdencrazy.com/EFILive/stockTunes.php.

Hope that at least gives you some insight.

Good luck..