Tweaking a tune with new injectors.

[pilihp2]

Best practice when going to bigger injectors? Go to a whole new tune, or just modify the req fuel amount and tweak VE settings as needed?
Hoping to start my buddies s4 tonight and we've gone from 440's to 850's. Engine has been completely rebuilt fresh and I'm hoping to not fuck anything up with the tuning during the break in period.
This is in a PNP vems urs4.

[EDIGREG]

Injectors have different characteristics at different pulse widths, so most of the time you will have to re-tune the fuel table. But changing req_fuel is a good place to start.

[boost_addict]

I change req fuel to new calculated amount.

make sure your using low basemap timing, & nothing from some tune u did on a dyno maxing the old setup out,

then I will add 5% before a bar. 10% between 1-2 and up on VE table. depends what the setup and what kind of jump in injector &/or other parts being changed too(turbo, manifolds, etc) but that's the basics.
should be pretty easy. take it slow and watch the lambdas and take a log. USE vems tune by statistics. Done.
most times u can just pull some back out on a log and your set., but its always better to be on the fat side of the money line, as I call it.

[pilihp2]

Well he had VEMS for a half a week before the motor decided to blow so base map timing wasn't even touched during that time period.
Appreciate the info guys. I'll tweak some things and we'll see if it starts tonight.