Injector data - how to determine values?

[16Victor]

We are using 42lb/hr injectors with the following specs:



I believe I can get correct info for injrampup_battfac using FNPW_OFFSET.

Can injopen (Inj Open Time @ 13.2V) or injocfuel (Injector opening effective rampup time) be determined?  I'm looking at the MINPW value above, 1.13ms, wondering if that value includes both open time and rampup time, and if so, how do I split that amount of time up into injopen and injocfuel?

Thanks,
Ron

[rob@vems.co.uk]

Its almost impossible to correlate these values into the VEMS injector model.
I would start without any guess work by turning it all off:
Inj open time @ 13.2V: 0
Inj effective rampup (us): 0
injrampup_battfac (us): 4080

Get the engine idling, then adjust the settings as part of the tuning.

[lugnuts]

To adjust the Inj Open Time, you need to do a test.
Make a run to a certain RPM, and apply a fair bit of load. You want the injector time to go to 3ms or more to get the injector in its linear range.
Anyway, when you pick a rpm/load spot, do a test run, and then add or subtract 10% fuel. The warmup table is handy for this. Then do the test again, and see if the Lambd is lower/higher by exactly 10%, or if it is 4% or 13% for example.
The correct dead time (Inj Open) will give you exacting results when you trim the fuel by XX%.

Andrey has a custom firmware with standard injector dead time vs. battery voltage setting. He also has an excel calculator that converts the VEMS settings into the more traditional numbers like you see on the chart.

[GintsK]

Tests is on the sheet above.

VEMS give inj opening time @13.2V So your opening time will be aprox. 750usec
Next battfact is pw adder @7.0V In your case theoretically ~3000usec. But don't use so aggressive value. Draw some graph of FNPW_OFFset and find some tangent in real life operational area of 11...14.5V and find out battfact point @7V from this tangent not real curve. It will give value about 600usec.

You can calculate this values regarding your fuel pressure.

Both other VEMS values you can ignore and leave zero values.

Here is my old investigation:

There is need for developers explanation...

My tests show something like this:

For injrampup battfact 4080:

PWefframpup=k*2/3*inj_eff_ramup_time

k=1.0@7V
k=0.90@10V
k=0.78@13V
k=0.737@15V
k=0.70@16V  It is straight line in fact!

If injrampup battfact is reduced, we get k closer to 1.0. As example:
 if 2040 used k=0.85@16V
if 0 - k=1.0 always
====
Battfact is in us bacause it is maximal adder to PW@7V. It linearly scales down to 0@13.2V.
It is straight line too!

Now what? Straight line+straight line=straight line anyway. Why there is two straight line equations used for descscripting one straight line?

Here can be some answer:

If active PW comes close to 2/3*inj_eff_ramup_time (at very low injection times), Inj_rampup becomes scaled down. Smaller PW cause smaller  Inj_rampup adder.

It is my free translation from Russian from Andreys description in http://rus.vems.hu/punbb/viewtopic.php?id=42

Here is original text:

Если pulse_width < 2/3*Inj_rampup, то есть при очень малом времени впрыска идет дополнительное масштабирование Inj_rampup в меньшую сторону, чем меньше pulse_width тем сильнее масштабирование.

How it exatly works is not clearly understandabble. Need additional bench tests. And very preferable some description of original idea.

http://195.159.109.134/vemsuk/forum/index.php/topic,661.30.html