Pe table question/ifr
11-30-2005, 11:34 PM
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Pe table question/ifr Okay question: If you change the Injector flow rate values to fit 36 # injectors vs 42 # injectors do the PE values still effect fuel the same way. I believe its a multiplier so If I adjust the IFR table from 42 # to 36# as long as the injector calibration is correct the PE values stay the same correct? They would still technically spray the same amount of fuel? Could it be correct to say as long the injectors are calibrated correctly the PE values still spray the same amount of fuel could someone please verify this? Thanks in advance.
Eric
Eric
11-30-2005, 11:42 PM
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Your fueling comes from an equation that reads many tables/sensors. Changing the injectors requires you to adjust all of the effected injector tables. But, this doesn't alter volumetic efficiency or the MAF because you're not altering the motor's ability to 'pump' more or less air. The only way it would affect those tables is if you were beyond the capabilities of the injectors. As for the switch and telling the computer you have 'X' injectors, it will still calculate the same amount of fuel needed. What changes is your injector pulse width/duration.
12-01-2005, 12:04 AM
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Just try to think like the PCM. 
Simply put, all PE does is tell the car what AFR to be at when you are at WOT.
However, in order to achieve that AFR the PCM has to have the correct data. All your other tables are going to do is tell the PCM how much airmass is in the cylinder. It takes that calculated airmass and divides that by what AFR you run and gets the amount of fuel to add. It then uses the IFR table to determine how long the pulse width needs to be to add the correct amount of fuel.
This is a VERY SIMPLIFIED idea of what is going on in there. Basically, if you don't have the IFR correct you won't get the correct air/fuel ration you are commanding via the PE table because the PCM doesn't really know how much fuel its putting in there. Of course, if your VE/MAF isn't right then it has no idea how much air is in there either... which is why we tune
Simply put, all PE does is tell the car what AFR to be at when you are at WOT.
However, in order to achieve that AFR the PCM has to have the correct data. All your other tables are going to do is tell the PCM how much airmass is in the cylinder. It takes that calculated airmass and divides that by what AFR you run and gets the amount of fuel to add. It then uses the IFR table to determine how long the pulse width needs to be to add the correct amount of fuel.
This is a VERY SIMPLIFIED idea of what is going on in there. Basically, if you don't have the IFR correct you won't get the correct air/fuel ration you are commanding via the PE table because the PCM doesn't really know how much fuel its putting in there. Of course, if your VE/MAF isn't right then it has no idea how much air is in there either... which is why we tune