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which ifr is right?



I have replaced my fuel injectors, map sensor, front o2 sensor, fuel pressure regulator, throttle position sensor, and maf sensor.


I am wondering if there is a way to test the fuel rails for correct pressure and flow, the diagnostic troubleshooting guide says the return line can get damaged from an incorrect engine movement, or maybe zzp's quality control sucks and their fuel rails failed prematurely.
 


I'm going to try putting the previous injectors I had in before the fuel trims went rich. I leaned my 42 lb injectors to a 40 lb/hour injector flow rate and the car starts better, so I wonder if I have a fuel pressure issue. I may try to install a fuel pressure gauge today and see what it looks like but I may not have time to do it.

with the 40lb/hour IFR my fuel trims come closer to 5% of 0 while driving better.
 
SgtMarshal said:
I have replaced my fuel injectors, map sensor, front o2 sensor, fuel pressure regulator, throttle position sensor, and maf sensor.


I am wondering if there is a way to test the fuel rails for correct pressure and flow, the diagnostic troubleshooting guide says the return line can get damaged from an incorrect engine movement, or maybe zzp's quality control sucks and their fuel rails failed prematurely.
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I usually go to the dealership for a diagnoses because they can usually say exactly what is wrong...


Haha...just messing with ya. Or am I?? :)
 
I talked with the service manager at the dealership, he didn't seem to happy about the idea of trying to figure out why it was running rich. Trust me, if that had been an option, I would have done it. I swapped a different set of 42 lb injectors in, and reset my fuel trims LTFT went to 0, STFT went to -25. drove around for about 35 minutes and while driving the LTFT went rich, like -20, but the STFT was usually about 5% within 0, so I think given enough driving my fuel trims might come back to where they should be.

Saturday I am driving 100 miles to get the custom tune done, we will start on the street, and then finish it on the dyno. something about driving 100 mph bothers me. I plan on coordinating with the tuner to take a scan with the hp tuner so we will have all that data to start with, maybe it will speed up the tuning process.
 
If your ltft locked in at 20, I don't think they will improve that much. But wudda I know? You taught me half of it, lol.

I had high ltft, but since you helped me figure out TM, my trims have been pretty nice. Still a little lean on decel, but not sure if its worth it to worry about. Seriously, one run through table modifier made them worlds better. Hope to get another session in tonight.
 
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decel is always going to be lean, the pcm is programmed to do that. I dont remember what my decel numbers were, but talking with the service manager at the dealership, he said they were going to lean out and to not worry.
 


SgtMarshal said:
I'm going to try putting the previous injectors I had in before the fuel trims went rich. I leaned my 42 lb injectors to a 40 lb/hour injector flow rate and the car starts better, so I wonder if I have a fuel pressure issue. I may try to install a fuel pressure gauge today and see what it looks like but I may not have time to do it.

with the 40lb/hour IFR my fuel trims come closer to 5% of 0 while driving better.
Click to expand...

if you wanted the computer to think that the injectors are smaller you need to tell the computer they are larger than they are. say your injectors are 100lb/hr for nice even numbers if you tell the computer they are 80lb/hr injectors given the same air flow the computer is going to think that it will need a longer pulse to get the same amount of fuel out to the cylinder. now if you tell the computer they are 120lb/hr the computer will think it needs a shorter pulse to deliver that same amount of fuel. so if you increase the IFR over what your injectors are rated you will get less fuel and if you decrease the IFR below what the injectors are rated you will get more fuel. (this is for HPtuners) for DHP the value of the numbers in the computer will do the exact opposite of what is described above.
 
NebTurboST5 said:
if you wanted the computer to think that the injectors are smaller you need to tell the computer they are larger than they are. say your injectors are 100lb/hr for nice even numbers if you tell the computer they are 80lb/hr injectors given the same air flow the computer is going to think that it will need a longer pulse to get the same amount of fuel out to the cylinder. now if you tell the computer they are 120lb/hr the computer will think it needs a shorter pulse to deliver that same amount of fuel. so if you increase the IFR over what your injectors are rated you will get less fuel and if you decrease the IFR below what the injectors are rated you will get more fuel. (this is for HPtuners) for DHP the value of the numbers in the computer will do the exact opposite of what is described above.
Click to expand...

so they are injecting more fuel with the ifr I have now. I like the hp tuner better, it is more intuitive. I'll go and change the ifr again.
 
NebTurboST5 said:
if you wanted the computer to think that the injectors are smaller you need to tell the computer they are larger than they are. say your injectors are 100lb/hr for nice even numbers if you tell the computer they are 80lb/hr injectors given the same air flow the computer is going to think that it will need a longer pulse to get the same amount of fuel out to the cylinder. now if you tell the computer they are 120lb/hr the computer will think it needs a shorter pulse to deliver that same amount of fuel. so if you increase the IFR over what your injectors are rated you will get less fuel and if you decrease the IFR below what the injectors are rated you will get more fuel. (this is for HPtuners) for DHP the value of the numbers in the computer will do the exact opposite of what is described above.
Click to expand...

I'm slow on the uptake sometimes, but this finally got through my skull. I changed the ifr to 47-50 and its not running near as rich. I might richen it up a little to somewhere around 45-48, but I want to see how it does after an hour of driving.
 
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