Injector Adjustment???
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Joined: Aug 2013
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Injector Adjustment???
Hey, last summer I had to replace my oil sender unit. As I was putting it all back together I cracked a few injector and it hasn't run the same sense. I have new injectors but I went with bigger injectors as I will eventually be upgrading heads can etc. this will be down the road a little ways yet. My question is,
Do I need to have the new 42# injectors duty cycles adjusted so the vehicle doesn't run rich, or will the PCM handle this?
Do I need to have the new 42# injectors duty cycles adjusted so the vehicle doesn't run rich, or will the PCM handle this?
Instructor
Joined: Mar 2009
Posts: 173
Likes: 3
From: Lenexa KS
You'll have to have the tune adjusted to run different injectors. The values defining the injectors are the foundation of the fuel model.
FWIW it isn't adjusting the duty cycle...duty cycle is a function of how much fuel is actually being delivered (derived from measured/calculated air mass, computation for target Lambda/AFR, then delivery based on the fuel model). Your tuner should change a number of tables that define the injectors.
FWIW it isn't adjusting the duty cycle...duty cycle is a function of how much fuel is actually being delivered (derived from measured/calculated air mass, computation for target Lambda/AFR, then delivery based on the fuel model). Your tuner should change a number of tables that define the injectors.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
When changing injector flow rates the only way to correct the fuel is to make the appropriate adjustment to your IFR table---otherwise a larger injector will make it run RICH
Also LS1 injectors are rated at 54 PSI most aftermarket ones are rated at 43 PSI---make sure you calibrate your new ones at 54 PSI or 4 bar-----
If you have stock ls1 28 lb injectors they are fine for up to 500 crank HP so no need to change---- a 42 LB injector which is a standard aftermarket mod is actually about a 48 lb injector on a LS1 system---way to big for a N/A engine
Also LS1 injectors are rated at 54 PSI most aftermarket ones are rated at 43 PSI---make sure you calibrate your new ones at 54 PSI or 4 bar-----
If you have stock ls1 28 lb injectors they are fine for up to 500 crank HP so no need to change---- a 42 LB injector which is a standard aftermarket mod is actually about a 48 lb injector on a LS1 system---way to big for a N/A engine
Pro
Joined: May 2014
Posts: 670
Likes: 46
From: Indiana
You can likely run the 42# injectors if you already have them, but as noted your tune needs to be adjusted.
I just replaced my 289,000 mile truck's blown 5.3 with a crate normally aspirated 6.0 that is supposedly good for 460 crank hp. Less fuel pressure than tblu noted above in that application so your mileage will vary, but as a reference point I'm getting a max duty cycle in that engine with the 42# injectors of about 60%.
I just replaced my 289,000 mile truck's blown 5.3 with a crate normally aspirated 6.0 that is supposedly good for 460 crank hp. Less fuel pressure than tblu noted above in that application so your mileage will vary, but as a reference point I'm getting a max duty cycle in that engine with the 42# injectors of about 60%.
Instructor
Joined: Mar 2009
Posts: 173
Likes: 3
From: Lenexa KS
Also, just to expand on it, there's a LOT that needs to be adjusted beyond just the injector flow rate to do it right. If you only change the flow rate your low pulse behavior will not line up with what you're telling the computer it will do...your tuner ends up bandaiding the tune by jacking around with the air model to correct for it.
Some things that may need adjustment:
Minimum pulse width
Default pulse width
Short pulse limit
Short pulse adder vs effective pulse width
Injector offset vs injpw vs map
Offset vs manifold vacuum vs vbat or offset vs differential fuel pressure or offset vs volts
Flow vs manifold vacuum or flow vs differential fuel pressure
I don't have HPTuners installed on my work laptop so I can't see which are correct for a genIII PCM, but the list actually changed should be a subset of what I listed above.
Some things that may need adjustment:
Minimum pulse width
Default pulse width
Short pulse limit
Short pulse adder vs effective pulse width
Injector offset vs injpw vs map
Offset vs manifold vacuum vs vbat or offset vs differential fuel pressure or offset vs volts
Flow vs manifold vacuum or flow vs differential fuel pressure
I don't have HPTuners installed on my work laptop so I can't see which are correct for a genIII PCM, but the list actually changed should be a subset of what I listed above.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
Also, just to expand on it, there's a LOT that needs to be adjusted beyond just the injector flow rate to do it right. If you only change the flow rate your low pulse behavior will not line up with what you're telling the computer it will do...your tuner ends up bandaiding the tune by jacking around with the air model to correct for it.
Some things that may need adjustment:
Minimum pulse width
Default pulse width
Short pulse limit
Short pulse adder vs effective pulse width
Injector offset vs injpw vs map
Offset vs manifold vacuum vs vbat or offset vs differential fuel pressure or offset vs volts
Flow vs manifold vacuum or flow vs differential fuel pressure
I don't have HPTuners installed on my work laptop so I can't see which are correct for a genIII PCM, but the list actually changed should be a subset of what I listed above.
Some things that may need adjustment:
Minimum pulse width
Default pulse width
Short pulse limit
Short pulse adder vs effective pulse width
Injector offset vs injpw vs map
Offset vs manifold vacuum vs vbat or offset vs differential fuel pressure or offset vs volts
Flow vs manifold vacuum or flow vs differential fuel pressure
I don't have HPTuners installed on my work laptop so I can't see which are correct for a genIII PCM, but the list actually changed should be a subset of what I listed above.
