1. Was the L31 injector that was measured an original poppet-type or the MFI upgrade type ?
The replacement injectors are saturated type as are the original. Electrical characteristics are close enough that they can be interchanged without a recalibration.
2. I plan on selecting MPFI mode in the PCM, so I would obviously wire the 4 injectors in paralell. But I would only perform the sense resistor mod and not need a resistor wired in paralell with the injectors, correct ?
Apples and oranges. MPFI mode refers to when the injectors are triggered in relation to the Distributor Reference Pulse. Peak and Hold or Saturated mode refers to the current control mechanism used when the injectors are energized. TBI injectors are typically peak and hold injectors but so are low impedance pfi injectors. 12 Ohms resistance typically puts the injectors in the "saturated mode" category.
3. I will take resistance measurements of the unit that I end up purchasing, but ultimately the driver circuit should be configured the same regardless of whether the injector assembly is the original poppet-style or the MFI upgrade, correct ?
Ultimately, a driver circuit configuration that works with one injector will work with the other.
4. I would like to better understand the process of how you determine the injector offsets with the charging system disabled.
I don't actually think I'd try it. Adjusting small PW offsets can be tricky enough without the added complexity of falling system voltage. I'd stick with adjusting the voltage scalars and leave the offsets alone.
I have a '99 L31 calibration for comparison. There are three tables of interest. Voltage correction to injector flow rate vs voltage, injector latency vs voltage, and small PW correction. For this cal I'd start with the flow rate correction vs voltage table.
Code:
Volt Correction
4.5 0.800
5.5 0.850
6.5 0.917
7.5 0.958
8.5 0.970
9.5 0.981
10.5 0.992
11.5 1.000
12.5 1.000
13.5 1.000
14.5 1.006
15.5 1.016
16.5 1.026
17.5 1.035
Since these values represent change in flow, and the $0D table represents change in time, you'll need to invert them (time = 1 / flow). As a sanity check, when the numbers are correct, the highest voltage values will have the smallest corrections. Here's the table with inverted values:
Code:
V Multiplier
4.5 1.25
5.5 1.176470588
6.5 1.090512541
7.5 1.043841336
8.5 1.030927835
9.5 1.019367992
10.5 1.008064516
11.5 1
12.5 1
13.5 1
14.5 0.994035785
15.5 0.984251969
16.5 0.974658869
17.5 0.966183575
Use Excel or another program to fit this curve to the voltage steps in $0D.
Small PW offsets look a little different than the typical TBI offset table:
Code:
ms offset
0.0 -0.34
0.2 -0.34
0.4 -0.34
0.6 -0.15
0.8 -0.07
1.0 -0.04
1.2 -0.04
1.4 -0.04
1.6 -0.04
1.8 -0.01
2.0 -0.01
2.2 -0.01
2.4 -0.01
2.6 -0.01
2.8 0.00
3.0 0.00
There are two other values to consider as well:
Base injector latency: .94ms
Low injector PW Correction Threshold: 2.49 ms.
The low injector PW correction threshold indicates that no corrections are needed below 2.49ms and it's easy to populate the $0D table with zeros from 2.44ms to 3.9ms. The negative values in the correction table may be the result of table biasing using the base latency of .94ms. I'd start by inputting the base latency value into Async Short BPW Offset Bias (as 940us) then populating the Async Short BPW Offset vs. BPW table with the values from the L31 (again, multiply them by 1000 to get microseconds).
Finally, there's the latency vs voltage change table.
Code:
4.5V 2.424
5.5V 2.234
6.5V 1.457
7.5V 1.167
8.5V 1.024
9.5V 0.926
10.5V 0.835
11.5V 0.761
12.5V 0.701
13.5V 0.653
14.5V 0.611
15.5V 0.578
16.5V 0.547
17.5V 0.549
This table may benefit from adjusting on the vehicle. Use Excel or another program to fit this curve to the $0D voltage correction table as a starting point. For this to work you must have the tune so it's good enough for the car to idle in closed loop with BLM and INT showing minimal corrections. The process to get actual changes is to idle the car in closed loop and disable the alternator. Monitor system voltage and BLM / INT. As system voltage approaches the next lower voltage in the correction table, adjust the table entry so there's no BLM / INT correction needed.
I've uploaded a new $0D definition file version 251 which properly biases the Async Short BPW Offset vs. BPW table table. You might want to head over to the $0D thread to get a copy. http://www.gearhead-efi.com/Fuel-Inj...ull=1#post2202
^^^^^^
Correct file should now be in place.
HTH.
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