I Am in Serious Need of Help
Registered User
Joined: Jul 2009
Posts: 310
Re: I Am in Serious Need of Help
So while I'm waiting on my next paycheck to dump into my baby lol, I'm trying to price out what all the possibilities are, and I have a quick question.
In the event that my injectors are the cause, I'm noticing that the psi on most of the more economically friendly injectors is significantly higher than stock even though they are listed as direct fit. Would I need a tune after installing these higher pressure injectors? Or would pcm adjust?
Again, this is Assuming that they end up being the problem (first thing I'm buying is a pressure Guage. Figure that could help me rule out some possibilities) instead of just throwing money blindly
In the event that my injectors are the cause, I'm noticing that the psi on most of the more economically friendly injectors is significantly higher than stock even though they are listed as direct fit. Would I need a tune after installing these higher pressure injectors? Or would pcm adjust?
Again, this is Assuming that they end up being the problem (first thing I'm buying is a pressure Guage. Figure that could help me rule out some possibilities) instead of just throwing money blindly
Prominent Member
Joined: Jul 2010
Posts: 1,520
From: Born on the Florida West Coast, now where can I retire?
Re: I Am in Serious Need of Help
So while I'm waiting on my next paycheck to dump into my baby lol, I'm trying to price out what all the possibilities are, and I have a quick question.
In the event that my injectors are the cause, I'm noticing that the psi on most of the more economically friendly injectors is significantly higher than stock even though they are listed as direct fit. Would I need a tune after installing these higher pressure injectors? Or would pcm adjust?
Again, this is Assuming that they end up being the problem (first thing I'm buying is a pressure Guage. Figure that could help me rule out some possibilities) instead of just throwing money blindly
In the event that my injectors are the cause, I'm noticing that the psi on most of the more economically friendly injectors is significantly higher than stock even though they are listed as direct fit. Would I need a tune after installing these higher pressure injectors? Or would pcm adjust?
Again, this is Assuming that they end up being the problem (first thing I'm buying is a pressure Guage. Figure that could help me rule out some possibilities) instead of just throwing money blindly
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Joined: Nov 1998
Posts: 71,099
From: Hell was full so they sent me to NJ
Re: I Am in Serious Need of Help
If the PSI at which the injector is flow rated is higher than the nominal 43.5 PSI (3 bar) at which the stock injectors are rated, you have a couple of options:
1 - buy an adjustable fuel pressure regulator and bump up the system pressure to match the pressure (PSI) at which the new, higher PSI are rated. In that way the injectors will actually flow their rated flow capacity (#/HR).
or
2 - run the higher pressure (PSI) injectors at the stock LT1 pressure (43.5 PSI), and calculate the new flow rating (#/HR) of the injectors. For example, LS1 injectors are typically flow rated for operating at 58 PSI (4 bar). An LS1 injector rated at 28.8 #/HR flow at 58 PSI will only flow 24.9 #/HR when operated at 43.5 PSI. Coincidentally, the same flow rate you will find in the stock PCM program. Flow rate correction is a function of the square root of P1/P2.
In any case, the new flow rate and injector offsets will need to be programmed into the PCM, as Gary indicates. Buying “economically friendly” (aka “cheap”) injectors is not a good idea. You can find an endless supply of what appear to be “Bosch” injectors on eBay, a set of 8 for less than $100. In fact, they are cheap Chinese counterfeits, totally lacking in quality. Just like buying a cheap Chinese rip-off $60 Opti.
PS: And you don’t have to drive the car to a shop to test the ICM. You just need to take the ICM.
1 - buy an adjustable fuel pressure regulator and bump up the system pressure to match the pressure (PSI) at which the new, higher PSI are rated. In that way the injectors will actually flow their rated flow capacity (#/HR).
or
2 - run the higher pressure (PSI) injectors at the stock LT1 pressure (43.5 PSI), and calculate the new flow rating (#/HR) of the injectors. For example, LS1 injectors are typically flow rated for operating at 58 PSI (4 bar). An LS1 injector rated at 28.8 #/HR flow at 58 PSI will only flow 24.9 #/HR when operated at 43.5 PSI. Coincidentally, the same flow rate you will find in the stock PCM program. Flow rate correction is a function of the square root of P1/P2.
In any case, the new flow rate and injector offsets will need to be programmed into the PCM, as Gary indicates. Buying “economically friendly” (aka “cheap”) injectors is not a good idea. You can find an endless supply of what appear to be “Bosch” injectors on eBay, a set of 8 for less than $100. In fact, they are cheap Chinese counterfeits, totally lacking in quality. Just like buying a cheap Chinese rip-off $60 Opti.
PS: And you don’t have to drive the car to a shop to test the ICM. You just need to take the ICM.
Prominent Member
Joined: Jul 2010
Posts: 1,520
From: Born on the Florida West Coast, now where can I retire?
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