Boost multiplier

[Lawso]

Ok, another question...

What does the boost multiplier actually do? I am helping out with a turbocharged holden 5lt and as such, need to understand what needs to be done to get it happening correctly.

The engine is fitted with twin turbos and 42lb injectors.

Now, normally with an NA engine, I would adjust the injector rate to get around 80-90% VE at MBT.
Should I be aiming for the same target, but at max boost? Or, does the multiplier affect the injrate? Or is it just trying to multiply the 100% VE?

[antus]

When you set the flags for 2 bar map, the 20-100kpa table does not need any modification, so what you are doing there stays the same. Ive not studied up on boost tuning with 12p yet myself, though I will be get getting in to that next week.

[Jayme]

Its the multiplier for the 100-200kpa ve table columns. Leave it as is, it can be adjusted to multiply an entire column to be richer or leaner if you have a rising rate reg for example. Ive done 2 boosted cars with 12p now and one had stovk reg and i left the multiplier table alone. The other had 2:1 rising rate so i adjusted the multiplier down a bit to compensate

[vn5000]

Yeah as jayme said ive always left it as it is and never had a prob.

[VL400]

The table is used to keep the VE below 100% under boost, without it you would be seeing up to 200% at 200kPa which the factory code wont allow - 8bit does not allow much resolution so 255 decimal = 100%. Its reason though is to offset the fuel pressure reduction from boost, if your using a 2:1 reg then you can adjust it to suit - default is for a stock reg. The table is used in GM factory turbo MAP code from the US, its call F77 in those. I have used it a little differently in that the table is not used until you enter boost, in the factory code the 100kPa value effects all off boost so had to be 0. You also have a boost VE table unlike factory code where the 100kPa column is your boost VE and the multiplier is used to adjust boost fueling.

[Lawso]

Thanks mate.

Makes sense now.