For anyone still using handheld diablo for 99-08, like myself, and wanting to or already have upgraded to larger or smaller injectors... Here is a simple equation to throw you in a very close range of where you should be...

To properly set up injector size changes it is recommended that you increase/decrease the current slope by injector % change.
Example:
24 lbs. injector to 30 lbs. injector
(30-24) / 24 * 100 = 25%
so you increase the injector slope by 25% to get you in the ballpark. If you are stepping down to a lower injector size than stock then you would decrease the injector slope by % change in injector size.


Determining long term fuel trims: Long term fuel trims are an accumulated (averaged) value received from the feedback of the Oxygen sensors (o2 sensors) of fuel added or subtracted during closed loop (part throttle) operation. The long term fuel trim ratings are abbreviated as LTFT1 and LTFT2 in the live data monitoring feature of the Predator. LTFT1 denotes the long term fuel trim for bank 1 and LTFT2 denotes the long term fuel trim for bank 2. These are not STFT1 or STFT2 which are the instantaneous samples taken by the o2 sensors. The samples taken by the o2 senors are aggregated and averaged into the long term fuel trims (LTFT1 and LTFT2). They will show values bouncing around that will never stabilize. That is why you want to monitor the averaged values in LTFT1 and LTFT2. To verify and tune for long term fuel trims, drive the vehicle for 30 minutes or until warmed up, monitor long term fuel trims until they stabilize and record/remember the average value. The easiest way to do this is to get on the highway, enable cruise control, and sit at 55-65mph while monitoring the data. Ideal values should be in the 0 to negative 2 (-2) range.

Once you get the average long term fuel trim value you need to make the following adjustments:
Positive long term fuel trims
For a positive value you subtract that value in percent in the Predator injector slope. It is also recommended to lean (subtract) both WOT (Wide Open Throttle) fuel tables by the same percentage.
Negative long term fuel trims
For a negative value you add that value in percent in the predator injector slope. It is also recommended to richen (add) both WOT (Wide Open Throttle) fuel tables by that same percentage.

Once adjustment is done and tune installed, take the vehicle out and verify the long term fuel trims per previously described method. Adjust again if necessary.

 

you would just have easily sent your info to Mike at Diablosport, and had him change your injector flow rates/settings in a custom tune.

after that was loaded, then you could have fine tuned LTFT's and PE settings

iirc, 25% was all the adjustment you have on injector slope with a predator, and if you really mod an engine, you are going to require larger than a 30lb injector to support the power combo.

i run 44 lb delphi's.... so that 25% end user adjustment would most likely not have sufficed.

just food for thought. Mike is very helpful there, and can/will do as much to your tune with info provided to get it as close as he can, leaving the fine tuning to the end user

any deeper with the modding, and a full tuning suite is the only way to go. e.g. heads/cam/intake/nitrous/etc.