Changing Injectors - Reqfuel or VE map alterations

[fizban]

Hello,
I am using 440cc injectors and going to replace to 750cc injectors. My current 440cc are simply to small (I get 100% duty cycle and i would also like to increase the boost)
my reqfuel is 6.2ms and this is my current ve map (currently the engine max load is 180 - with current boost):


Should i just remove the reqfuel to compensate or alter all the ve map. The refuel is the easier way but i understand that the resolution of  changes is bigger, when changing only the req fuel.
what do you think?
BTW - currently,  engine load is 160-190kpa - depends on my boost controller settings. I intend to go up to 230. Rev limiter at 7000rpm. Full boost is around 3500-3600rpm.
Thanks,

[jrussell]

If the car is tuned well already, I would just rescale the reqfuel. 440cc/750cc = .58, 6.2ms * .58 = 3.6ms new reqfuel. You may have to "tune" the new injector open time, ramp-up, voltage compensations, etc. to get them to act perfectly linear. From the looks of your map, you didn't do that with the 440's. It's not necessarily a problem, but with proper injector calibration, the map is nearly flat. I have a feeling your in-boost fueling is very rich.

[fizban]

Hi,
Thanks for the reply!
The car is not tuned well. You are right about the in-boost fueling. it is now set on 10.6:1.
But even with 11:7:1, of course, the DC is at 95%. It is not healthy and therefore my rev limiter is at 6K RPM instead of 7K. Until I deal with this.
You were also right about the injectors open time. Originally the map was built for 215CC Bosch injectors. After adding the force induction, i replaced them with new Ford sport 440CC.
I would very much like to learn how to "tune" the injectors. Can you provide a link to relevant documentation?
Thanks

[fizban]

Hi again,
I've replaced the 440cc with 750cc. I indeed used 3.6 reqfuel, but since i also changed to fuel pressure regulator from 3.5bar to 3 bar (to get better idle), i increased the reqfuel to 4.1 and the transition was very (and surprisingly) smooth.
PW in idle is around 1.2/1.3ms (RC injectors) and idle is ok at 950 rpm.
So if  i understand you correctly, the values in the VE tables should stay ~identical if i go up in the rpm band, and only change when i move across the engine load axis - if the injectors are tuned?
I removed a lot of fuel and still i get around 0.74 lambda in boost (i am aiming for 0.79 or 0.77) - maybe its because i thought i should increase fuel in rpm axis.
Here is a snapshot of my fuel and timing. I am not sure the timing is right (i think i retarded it too much in boost - just to be safe)





I also have some logs of runs, but i guess that if my map is not good enough, there is no point of uploading them, yet.
Thanks.

[gunni]

Make sure your injector dead time is configured right, if it is then no changes should be needed, but that usually isn´t the case. So you will almost always need to make some VE table changes

[fizban]

I am using 1.1.63 -  is there a dead time feature there?

current setting are:
opentime 13.2v - 0
rampup 960
rampup voltage compensation - 4080
voltage compensation - 256

There are a lot of fluctuations at light load 2100-3500rpm. You can  see it in the ve table 
I am working on it all the time, taking logs and updating the tables accordingly. At least until i set a dyno day