Injector BPC Affect Cranking BPW

[Dylan]

I've doing some tuning and wondering if altering the injector bpc affects the cranking fuel?
From my understanding VE and AFR has no affect it's just a time in ms?

[antus]

That is correct. There are no calculations in the operating system - it is purely a time in milliseconds. You need to adjust both cranking fuel tables by the % change of the flow rate of the injectors. Similar logic applies for alternate fuels, as well as engine capacity changes if moving the tune to a different engine. If you change several of these things at once, calculate the corrections and apply them one after the other.

For $12P:
Map A: Crank - First Stage Crank Base Pulse Width vs Coolant Temp
Map A: Crank - Second Stage Crank Base Pulse Width vs Coolant Temp

[Dylan]

Thanks Antus. When doing a write cal in flash tool is the injector bpc written if it's been updated?
After a day of tuning yesterday I noticed the injector bpc missed an update, maybe I forgot to save it.

[antus]

Yes, all the calibration is in the cal segment and will be flashed in.

[Dylan]

Thanks i obviously missed a save or hit wrong number.
I wanted a bpc of 0.13 but ended up with 0.15. Is there an easy way to re scale the ve after changing? Ive got the curve pretty right but peak ended up around 85%.
I was wondering why it was low.

355 with 24lp injectors come in at 0.12 on the calc so i was going for 0.13 for head room.

[VL400]

You can divide the VE table by the same amount the BPC has changed.

So 0.15/0.13 = 0.866
Select the entire VE table and divide it by 0.866. It will make 85% values very close to 100% though.

[Dylan]

Awesome thanks! I thought you could do something like that with the percentage change.
Thanks guys!

[Dylan]

You can divide the VE table by the same amount the BPC has changed.

So 0.15/0.13 = 0.866
Select the entire VE table and divide it by 0.866. It will make 85% values very close to 100% though.

Thanks mate I appreciate your input. Im no maths genious but I got a figure of 1.15 when doing that calc.
Have I missed something?

[Jayme]

yeah he meant old BPC/new BPC so 0.13/0.15
easy way to remember is if you make BPC go up then you need to make VE go down, so just divide it in the direction that does that

[vlad01]

Just a question, say you change your injectors to ones that flow 5% less, do you multiply the cranking PW values by 1.05?