BMW M20 Injector wiring

[Sam8888]

Hi there!

I'm about to convert my M20B25 to VEMS.

How should i do the injector wiring? Motronic using 2 batches originally (3-3), but if i use it like that, the amount of current will be bigger than if it's only one injector connected to one output.
So should i use it just like that? Hook up the two batches to two injector outputs and that's it? Any modifications needed in the ECU for that? Or should i just wire them individually?

I've read myself through the manual, and googleing around for about two weeks for the VEMS, now i guess i'm ready to do it, but didn't found any info from that...

Thanks

[VEMS]

Hello Sam8888,

It is recommended to use one injector output per injector, to make use of functions like: individual injector trim, per bank ego control, injector end angle control etc.
But joining 3 High-Z injectors one one injector output is also supported however limits in functions listed above.

Best regards, Dave

[Sam8888]

Okay, thank you for the answer. I don't want to use those functions, so that doesn't bother me.

Although on the required fuel calculations, since i have 2 injector output in use with 3 injectors each, i have to calculate this like:

6,49x(2500[engine displacement]/2[since i have 2 banks]/690[i want to use 230cc/min injectors, but in two banks, so 3x230=690]

Am i right with these calculations?

That'll be ~11,7ms.

[gunni]

It depends on if you plan on opening the injectors twice or once per cycle.
If you open twice you loose the dead time from the available opening time per cycle, not a big deal until you get to higher rpm and generally not a big deal.

You still only have 6 injectors and 230cc each

(2500/230/6) * 6.49 = 11.75ms

If you open twice per cycle vs once the fuel VE numbers will be halfed, so you could half the req_fuel value and maintain a normal looking fuel table.

If you open the injectors twice per cycle make sure you get the dead time very good as its now double effective and needs to be accurate for good closed loop fuel control and so that all y% changes are in fact going to change the lambda by y%

[Sam8888]

Thanks Gunni!

It depends on if you plan on opening the injectors twice or once per cycle.

What are the benefits of two opening per cycle?

I guess i can set this up with the injector divider set to 2 on the Injector settings page?

[gunni]

The fuel will be distributed twice per cycle so that wets the port better as injection timing by opening 3 at a time will only really work well for two of them and not the last one.

i.e open for cyl1 and 6 and then also 4 perhaps, the cyl4 is not timed the same as 1 and 6,

I´d just stick to once per cycle