Author Topic: injector rampup trick?  (Read 26422 times)

Offline z0tya

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injector rampup trick?
« on: May 20, 2010, 02:48:52 pm »
Is it possible to use bank/sequential injection method to find out the injector rampup characteristic?
In bank there is twice as injection per revolution than in sequential, so there is no diff in lambda when the rampup time is right swithc from bank to seq and bank isn't it?
(DTA has a injector characteristic setup method, when it is switch to 2 stroke / 4 stroke mode cyclic, and show lambda gauge.)


Would be nice a similar method in vemstune... :)

Offline multiplex

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Re: injector rampup trick?
« Reply #1 on: May 20, 2010, 04:06:33 pm »
thats a pretty cool method.  Don't most people set ramp up to zero?  (not that is ultimately correct)

is there an easy way to switch from sequential to batch in vems?  feels like you'd have to change a few things, but i'm not sure what.


Offline [email protected]

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Re: injector rampup trick?
« Reply #2 on: May 20, 2010, 09:20:05 pm »
To go from sequential to batch just change your injector outputs.

It seems like its doable

Offline z0tya

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Re: injector rampup trick?
« Reply #3 on: May 21, 2010, 07:07:57 am »
thats a pretty cool method.  Don't most people set ramp up to zero?  (not that is ultimately correct)

is there an easy way to switch from sequential to batch in vems?  feels like you'd have to change a few things, but i'm not sure what.



I am using Bob's user guide:
"
While VEMS takes care of the amount of Injector open time based on its fueling calculations, it needs to factor in the open, ramp up and ramp down times, or too little fuel is added. These times are also voltage dependent as a higher voltage will energise a coil quicker, so we must factor in battery voltage to ensure that the AFR does not lean out with low voltages.

    * Inj open time @13.2V (us)
    * Inj effective rampup (us)
    * Inj rampup_battfac (us)
    * battfac (us)

When using a Transient supression diode

    * Inj open time should be 0,
    * Inj rampup_battfac must be 4080 (which diables the feature)

"

So I set open time to 0, effective rampup to ~900, rampup_battfac to 4080 and battfac ~400 with most of injector (with siemens 630 too), but now I need to raise the eff_rampup to 1200 with siemens 840 because the ve was lumpy with 900 ms..

Offline Wayne

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Re: injector rampup trick?
« Reply #4 on: May 21, 2010, 08:35:15 am »
There is an other method to find the ramp up value.

You can measure the current of the injector with the oszi,
you can see the edge in the current, (blue line) when the
injector is fully open and the current goes down.


3sgte gen3 injector ramp up

Offline GintsK

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Re: injector rampup trick?
« Reply #5 on: May 21, 2010, 09:50:00 am »
There is an other method to find the ramp up value.

You can measure the current of the injector with the oszi,
you can see the edge in the current, (blue line) when the
injector is fully open and the current goes down.

It is not enough. Values in tuning program describes real injector [opening AND closing = flow pulse] versus electrical pulse. So we have to watch also on closing delay not only opening. It is visible on voltage scope. So injector "lag" will be [opening delay-closing delay]. Many modern injectors have "lag" below 0.5ms.

I always leave inj eff rampup time and  ramp-up voltage compensation as zero and insead configure inj open time @13.2V. and Injector voltage compensation. These are straightforvard values instead both others:
I do not knew is something changed in newer firmwares but in older ramp-up time was non-understandable value with no clarification. Same with ramp-up voltage compensation. Both is not clarified nowhere in English documentation. I found some clarification in Russian.

Here is what I found some time ago:
I do some labor work regarding injector settings.

But surprise!!! injrampup_battfac 4080 did not disable correction. It is maximal possible correction in fact!!
injrampup_battfac works in very strange way. It describe some kind of coefficient for inj_eff_rampup time. No influence @7V.
If inj_eff_rampup time is configurated as 1500, it adds 1000us @7V. But injrampup_battfac scale this value @13V by aprox. :
4080 - 0.78
2000 - 0.89
500 -   0.97
0    -   1.0

So if injrampup_battfac is 4080 and inj_eff_rampup time is configurated as 1500us we get 1000*0.78=780us adder to PW @13V. (1000=2/3*1500)
Very confusing and user unfriendly! Why, why ??? ??? ??? ???

Both other settings are more straightforward:
Inj_open_time @13.2V is simple adder at any voltage. 1:1. 500us=500us
Battfact is PW added @7V It scales down to 0us @13.2V.

Gints
And from same topic:
There is need for developers explanation...

My tests show something like this:

For injrampup battfact 4080:

PWefframpup=k*2/3*inj_eff_ramup_time

[email protected]
[email protected]
[email protected]
[email protected]
[email protected]  It is straight line in fact!

If injrampup battfact is reduced, we get k closer to 1.0. As example:
 if 2040 used [email protected]
if 0 - k=1.0 always
====
Battfact is in us bacause it is maximal adder to [email protected] It linearly scales down to [email protected]
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:
Quote
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:
Quote
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 understandable. Need additional bench tests. And very preferable some description of original idea.

Offline Sprocket

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Re: injector rampup trick?
« Reply #6 on: May 21, 2010, 07:03:13 pm »


Considering the general consensus to set the open time to zero, I found this interesting http://www.calibratedsuccess.com/Assets/Documentation/Fuel%20Injector%20Article.pdf

I personaly made an effort to calculate a reasonable assumption for all values, and my findings are found in the same topic that the above extracts/ quotes were taken.

Offline ryniobl

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Re: injector rampup trick?
« Reply #7 on: May 23, 2010, 10:16:03 pm »
This is the only way.
On my scope it looks like this

http://picasaweb.google.com/ryniobl77/Oscillograms#5474584213859532642

More info here http://automotivetestsolutions.com/images/escope/fuelingectortutorial/FuelInjectorWaveforms.htm

There is an other method to find the ramp up value.

You can measure the current of the injector with the oszi,
you can see the edge in the current, (blue line) when the
injector is fully open and the current goes down.


3sgte gen3 injector ramp up

« Last Edit: May 23, 2010, 10:22:00 pm by ryniobl »
/Richard

Offline GintsK

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Re: injector rampup trick?
« Reply #8 on: May 24, 2010, 12:35:44 pm »

Both scope-shots looks just on injector opening phase, but calculations in ECU relates to closing delay too.
Closing is also described in http://automotivetestsolutions.com/images/escope/fuelingectortutorial/FuelInjectorWaveforms.htm

ryniobl, why the only way??
We can find right values with changing injector pulses per cycle (may be not so good for big injectors).
Or calculate values from static and dynamic flow difference.

Gints



« Last Edit: May 24, 2010, 12:53:12 pm by mattias »

Offline ryniobl

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Re: injector rampup trick?
« Reply #9 on: May 24, 2010, 03:08:07 pm »
I mean its the accurate way.I was never satisfied with changing pulses per cycle.


Both scope-shots looks just on injector opening phase, but calculations in ECU relates to closing delay too.
Closing is also described in http://automotivetestsolutions.com/images/escope/fuelingectortutorial/FuelInjectorWaveforms.htm

ryniobl, why the only way??
We can find right values with changing injector pulses per cycle (may be not so good for big injectors).
Or calculate values from static and dynamic flow difference.

Gints




/Richard

Offline dnb

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Re: injector rampup trick?
« Reply #10 on: May 24, 2010, 08:10:44 pm »
Changing the pulse length doesn't give much change with big injectors, so you end up trying to estimate a big thing with two very small numbers.  This often doesn't work well...

Offline mads b (dk)

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Re: injector rampup trick?
« Reply #11 on: May 20, 2014, 02:55:54 am »
Was it possible to use the method in the first post to "calculate" inj ramp up time ?
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Offline mads b (dk)

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Re: injector rampup trick?
« Reply #12 on: May 22, 2014, 12:31:13 am »
What about this method http://blog.nsfabrication.com/2010/02/09/measuring-injector-dead-time-part-1/

do vems have the output test with the possiblity to set injector open time like the MEGASQUIRT in the link  ?
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Offline MWfire

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Re: injector rampup trick?
« Reply #13 on: May 23, 2014, 01:57:01 pm »
IMHO the easiest way to do that is:
do{
put labmda target at idle(stable) to 0.9
map VE to have 100% ego correction
change lambda target to 0.8
if now lambda is over 0.8 then you need do decrease dead time(and remap VE table), uder 0.8 increase deadtime(and remap VE table)

while(lambda=0.8 with lambda target 0.8 and lambda=0.9 with lambda target=0.9}



Offline mads b (dk)

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Re: injector rampup trick?
« Reply #14 on: May 23, 2014, 03:42:55 pm »
IMHO the easiest way to do that is:
do{
put labmda target at idle(stable) to 0.9
map VE to have 100% ego correction
change lambda target to 0.8
if now lambda is over 0.8 then you need do decrease dead time(and remap VE table), uder 0.8 increase deadtime(and remap VE table)

while(lambda=0.8 with lambda target 0.8 and lambda=0.9 with lambda target=0.9}


Thanks :-)
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