bruce said:
Let's see, F.A.S.T. claimed a true VE table, and ideal gas law as a selling point, and then you have to guess, or approximate the injector openings. It sounds like in the end, weither it's a true of VE table is actually moot, since there's so much guessing or fudging of numbers to get the system to work (VE tables to line up with reasonable values).
Can someone shine some light on why if you have to guess/ fudge the entries, why it's better then a well designed BPC, or BPW calculation style of calculation?.
First of all BRUCE wouldn't it be NICE for all the INJECTOR MFG'S to SPECIFY what their Minimum Injector Opening Times were??? Even if they did it would be subject to slight change due to conditions.
Lets see 160#, 95#, 83#, 75#, 72#, 65#, 60#, 57#, 55#, 50#, 42.5#, 40#, 38#, 36#, 32#, 30#, 28#, 19#, 17# Injectors. These seem to cover most used. Then there are the differences relating to high impedance and low impedance etc, Not to mention the constantly varying volatge changes & loads the injectors are operated under.
For your information, I am listing below what is printed in the FAST Help/Manual regarding Minimum Injector Opening Time:
6.2.6 Injector Opening Time (ms)
You should not have to change this parameter with most popular engine applications. Always start at 1.0 ms.
This parameter defines the amount of time that it takes from the instant that an electrical signal is applied to a fuel injector until fuel actually flows from the injector.
This value is added to the base pulsewidth value to compensate for injector opening delays. Because the base pulsewidth value is always changing and this value is constant, the effects of changing this setting will be most pronounced where the base pulsewidths are smallest - typically at idle and light cruise. Here is an example.
Let's assume the engine is idling, and the base pulsewidth value is 3.0 milliseconds. The injector opening time is set to 1.0 millisecond. These two values will be added together, and the reported pulsewidth will be 4.0 milliseconds. If you were to increase the injector opening time by 0.5 milliseconds, the new reported pulsewidth would be 4.5 milliseconds - a 12.5% increase.
Now let's assume that with this same calibration, the base pulsewidth at full throttle and 5000 RPM is 20.0 milliseconds. With an injector opening time of 1.0 millisecond, the reported pulsewidth would be 21.0 milliseconds. Increasing the injector opening time by 0.5 millisecond as in the last example yields a new reported pulsewidth of 21.5 milliseconds - a mere 2.5% increase!
The actual time an injector takes to open will vary slightly as battery voltage fluctuates. Higher battery voltages will open an injector faster, so the injector opening time will be reduced to compensate for this. Alternatively, as battery voltage decreases, an injector will be slower to open. The injector opening time is increased to make up for this. Note that this battery correction only applies to the “Injector Opening Time” – the extra time that is added to the base pulse width value to compensate for injector opening delays. The base injector pulse width calculated by the ECU is not changed. The opening time will be modified as per the following graph:
"UNABLE TO POST GRAPH"
To my & all others knowledge, all ecu manufacturers, including OEM, have to deal with the same issues as it relates to varying conditions etc., and appropriate corrections are applied to compensate.
Joe