BPW change with bigger injectors

[immortality]

Hi guys,

Started doing some tuning on my mates 355 with small cam.

Once the engine is running all is fairly well but starting is very hard. Once it starts it blows black smoke for a bit.

I'm fairly certain I need to change the BPW tables to suit the new bigger injectors but I thought I'd better confirm.

The old injectors were the standard ones which I think are about 19lbs or 150 g/min, the new injectors are 34lbs or 260g/min.

So if I divide the old injectors value by the new injector value and then alter the BPW tables by the same amount it should be about right (for the injector change) or

150/260 = 0.5769 (multiply the original BPW tables by this number).

Then there is the matter of the engine configuration change. Seeing as he's stroked the engine from 304 to 355 cubes it's going to draw more air during cranking so this would probably require a little more fuel during cranking?

Cheers

[VL400]

I would start with multiplying the cranking PWs by about 0.7 to allow for the injector change and displacement change. It should get you close and can adjust it from there. The VE might be out in the higher MAP area it fires in so could be overfueling due to being loaded up with fuel?

If after adjusting the cranking PW it fires quickly from the cranking fuel but then runs rich for a few seconds can adjust how the initial AFR increases from a rich offset to the cold engine table or target AFR table value.
"Map X: A/F Ratio - Initial Run A/F Ratio Offset vs Coolant Temperature" - The initial AFR offset (subtracted from the cold engine/target AFR value) before running
"A/F Ratio - Run A/F Time-Out Interval Vs Coolant Temp" - how long it takes to decay the offset to zero after the engine is running.

[immortality]

Cheers mate.

A ended up going with about .73 which is the injector change + 16% increase for the extra cubes.

Guess we'll find out how well it works in a couple of days.