N Alpha

[wrench459]

Could ya'll help a silly old fart understand..
Ok the N-Alpha is a crude way of measuring load.
Then theres speed density and mass air flow/seqential or so I thought.
My question is how are they firing the injectors in order in a speed density system? Or does it matter?

[davegt27]

After hours and hours of looking on the Internet it turns out that Alpha-N is another term for speed density


Or FI based on Throttle position

Mass Air flow is hot wire
AFM (75 FI) is Air flow meter other people call it something else but Bosch calls it AFM

Now how the injectors are fired

One way batch fire (all 4 injectors’ fire at the same time)

Sequential fire one at a time

Basically 12V rests on one side of the injector and an injector driver (transistor) is used to apply a ground (or signal low) to the other side of the injector and it fires


HTH
Davegt27

[oldopelguy]

The Opel EFI system, and as far as I know all EFI systems prior to about 1989 were batch fired, meaning all the injectors fired at the same time. Sequential EFI requires a crank and usually cam position sensors, and a much more sophisticated system. Batch fire isn't a bad thing, really, since all carb and throttle body EFI systems are supplying fuel all the time as well and seem to work just fine.

[markandson]

MegaSquirt is batch fire but you have 2 injector driver circuits so you batch fire half the cylinders at a time. So in the case of our Opels we are injecting into 2 cylinders at a time.

Alpha-N Blending: Older MS-II code only allows alpha-N below lo_rpm, a blend between lo_ and hi_rpm, and speed density above hi_rpm. However, the 2.8 code allows you to reverse this so you have speed density at low rpm but alpha-N above hi_rpm. The first setup is for big, "lopey" cams at idle, the second for when MAP peaks to 100 as soon as the throttle is cracked and there is no more load control unless you use alpha-N. There is also added a factor to allow spark advance with baro (when less than 100 kPa) for alpha-N mode. This isn't allowed in speed density since map in the spark table accounts for it. The rate of advance versus baro under 100 kPa is a user input

[wrench459]

Thank you very much.
At first I saw the 4 drivers pins 32,33,34 and 35. After looking at the PCB theres only two injector drivers.
While this helps in my application it got me to thinking about another problem child.
It has to deal with flybacks and cold restarts.
Now I'll need more reading time....