PCM Re-Tune For Just An Injector Size Change?
03-27-2012, 05:14 PM
#1
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PCM Re-Tune For Just An Injector Size Change? I posted this over on CamaroZ28 and the link to that thread is here:
http://www.camaroz28.com/forums/lt1-...pgrade-857765/
But my question is:
If you already have a good "mail order" tune for a somewhat modded car (see signiture), and all you want to do is "upgrade" to a larger size fuel injector, what all needs to be changed in the PCM tune?
TIA for any replys here!
http://www.camaroz28.com/forums/lt1-...pgrade-857765/
But my question is:
If you already have a good "mail order" tune for a somewhat modded car (see signiture), and all you want to do is "upgrade" to a larger size fuel injector, what all needs to be changed in the PCM tune?
TIA for any replys here!
03-27-2012, 05:29 PM
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03-27-2012, 10:19 PM
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If the mail order tune was running properly, then you dont need a bigger injector. If it wasn't, then you will need a retune after the injectors anyway because it was likely demanding a bunch of pulse width to meet the fuel demands.
Regardless, if you actually do need to swap injectors.... in TunerCats you would go under the ECM Constants you update the new injector flow rate.
There is a spread sheet / calculator out there (search for it) that will give you the data for SVO injectors. Ford bases it on 40psi IIRC and LT1 is 3 bar or 14.67 * 3 = 44.01psi (actual will vary).
The spreadsheet also gives you offset data IIRC. If not you should be able to find it online somewhere as popular as those injectors are.
You would adjust that under the table "Injector offset vs Battery Voltage".
03-28-2012, 10:56 AM
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Agree 100%
If the mail order tune was running properly, then you dont need a bigger injector. If it wasn't, then you will need a retune after the injectors anyway because it was likely demanding a bunch of pulse width to meet the fuel demands.
Regardless, if you actually do need to swap injectors.... in TunerCats you would go under the ECM Constants you update the new injector flow rate.
There is a spread sheet / calculator out there (search for it) that will give you the data for SVO injectors. Ford bases it on 40psi IIRC and LT1 is 3 bar or 14.67 * 3 = 44.01psi (actual will vary).
The spreadsheet also gives you offset data IIRC. If not you should be able to find it online somewhere as popular as those injectors are.
You would adjust that under the table "Injector offset vs Battery Voltage".
If the mail order tune was running properly, then you dont need a bigger injector. If it wasn't, then you will need a retune after the injectors anyway because it was likely demanding a bunch of pulse width to meet the fuel demands.
Regardless, if you actually do need to swap injectors.... in TunerCats you would go under the ECM Constants you update the new injector flow rate.
There is a spread sheet / calculator out there (search for it) that will give you the data for SVO injectors. Ford bases it on 40psi IIRC and LT1 is 3 bar or 14.67 * 3 = 44.01psi (actual will vary).
The spreadsheet also gives you offset data IIRC. If not you should be able to find it online somewhere as popular as those injectors are.
You would adjust that under the table "Injector offset vs Battery Voltage".
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03-28-2012, 11:18 AM
#8
GIZMO, well maybe(?) I'm not fully understanding your post here? If I datalog injector "duty cycle" vs engine RPM and the smaller injectors duty cycle hits 100% at say 6,200 RPM, and the engine then starts going lean air-fuel ratio wise only at engine speeds above 6,200 RPM ............ then isn't that injector "maxed out"????
03-28-2012, 12:02 PM
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GIZMO, my current "situation" is that I got a good deal on Ford SVO 42 lb/hr fuel injectors over the Winter, and, in past data logs of my engine, running my current Ford SVO 30 lb/hr injectors .......... I'm seeing duty cycles of 100% at higher, (about 6,200/6,300 plus), RPM.
This got me to thinking that installing the bigger injectors, and dropping that duty cycle back into the 70/80% range at maximum RPM (about 6,700/6,800 for my car) ................... was worth doing???
The injector swap is, of course, a "no brainer" for me to do ........ it's re-programing that darn PCM for the larger injectors thats got a tuning "newbie" like me ................ starting this thread.
This got me to thinking that installing the bigger injectors, and dropping that duty cycle back into the 70/80% range at maximum RPM (about 6,700/6,800 for my car) ................... was worth doing???
The injector swap is, of course, a "no brainer" for me to do ........ it's re-programing that darn PCM for the larger injectors thats got a tuning "newbie" like me ................ starting this thread.
Last edited by 97 6speed z; 03-28-2012 at 12:13 PM.
03-28-2012, 03:54 PM
#10
GIZMO, my current "situation" is that I got a good deal on Ford SVO 42 lb/hr fuel injectors over the Winter, and, in past data logs of my engine, running my current Ford SVO 30 lb/hr injectors .......... I'm seeing duty cycles of 100% at higher, (about 6,200/6,300 plus), RPM.
This got me to thinking that installing the bigger injectors, and dropping that duty cycle back into the 70/80% range at maximum RPM (about 6,700/6,800 for my car) ................... was worth doing???
The injector swap is, of course, a "no brainer" for me to do ........ it's re-programing that darn PCM for the larger injectors thats got a tuning "newbie" like me ................ starting this thread.
This got me to thinking that installing the bigger injectors, and dropping that duty cycle back into the 70/80% range at maximum RPM (about 6,700/6,800 for my car) ................... was worth doing???
The injector swap is, of course, a "no brainer" for me to do ........ it's re-programing that darn PCM for the larger injectors thats got a tuning "newbie" like me ................ starting this thread.
03-28-2012, 07:38 PM
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duty cycle isn't how long the injector is open... it is the calculated time of open time/time available. The time available decreases as engine rpm goes up.
You could up the fuel pressure if you are having "duty cycle" problems... But if you aren't going lean then the injectors are fine.
You could up the fuel pressure if you are having "duty cycle" problems... But if you aren't going lean then the injectors are fine.
03-29-2012, 08:00 AM
#13
I will admit that I don't know a darn thing about the stock computer and how you are logging, but there is no way that you are maxing out 30 lb SVO injectors with your combination. If it were mine I would run 24's. If you are serious about performance you are going in the wrong direction. There is nothing wrong with a 100% duty cycle for short periods.
And SVO 30's are fueling just fine on up to 500 rwhp combo's with the stock computer.
03-29-2012, 08:21 AM
#14
gregrob and gizmo along with everybody else in here are completely right....also what i agree on the most is i cant see how you are maxing out 30lb injectors right now......my GTO with stock LS2 injectors is making 420+rwhp shifting at 6800rpm and im seeing 85-90% DC with a smaller injector.......i ran 30lb injectors in my 355 LT i used to have in my car with TFS heads and a healthy cam with good compression and never maxed them out and i was running 120+mph traps at 3450lbs shfiting at 6800 in the mid 11's........im wondering if your tune is excessively rich and using far too much injector.....whats your AFR's at WOT above 4500rpm??
Last edited by quik95lt1; 03-29-2012 at 08:27 AM.
03-29-2012, 08:34 AM
#16
running low Z injectors now ......problem solved
03-29-2012, 11:03 AM
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Guys, I got the information I requested in my original post from a thread in another forum, but ........... I did want to stop back and sincerely thank those of you who also replied here.
Thanks (again) to all who responded!
Thanks (again) to all who responded!
