Fuel injector duty cycle diagnostic
Fuel injector duty cycle diagnostic
This was brought up recently in another post, I decided I had to have it.
http://www.cardomain.com/member_page...562_9_full.jpg
ref: http://www.impconcepts.com/fuelinjec...torforsale.htm
http://www.cardomain.com/member_page...562_9_full.jpg
ref: http://www.impconcepts.com/fuelinjec...torforsale.htm
Originally Posted by ejj
So what's it telling you with your current setup?
So how exactly does this work?
I may be way off, but isn't 'duty cycle' how long out of the time available for the injector to spray that it does spray?
If so, isn't/couldn't that be different for every car?
I may be way off, but isn't 'duty cycle' how long out of the time available for the injector to spray that it does spray?
If so, isn't/couldn't that be different for every car?
Originally Posted by DA-MAX
duty cycle is "how hard" the injector is working(% wise) and since its reading off the injector signal wire which all cars have its pretty much universal
Originally Posted by ejj
An injector is either opened or closed, it can't "open hard", correct? So, isn't "how hard" its working a measure of the time that its open?
The duty cycle indicator is pretty neat. In normal driving usually only the first LED lights up. Accelerating lights up two or three LEDs, and they all go out when I let off the gas pedal. I don't ever see the amber LEDs (70-80% duty cycle) light up unless I'm boosting. The first red LED (90%) lights up right after the MEVI opens. So far I haven't seen the last LED light up, but I've got my bov set to leak and limit boost to 10 psi.
Originally Posted by Stephen Max
That's right, Eric. A duty cycle of 50% means the injector is open 50% of the time, 100% means it's open all the time and you are getting maximum flow through the injector (for the particular fuel pressure you're at).
Originally Posted by ejj
So how does the unit know what % of the available cycle the injector(s) are open? That "window" (cycle length?) can't be the same on every engine.
Originally Posted by Stephen Max
I think it just compares the amount of time the injector sees current compared to the amount of time it doesn't. That's pretty much the definition of duty cycle and is the same for every type of injector.
Originally Posted by ejj
But, wouldn't it never see current during 3 out of the 4 strokes (intake stroke)?
There is a specific term for this, but I forget what it is. I think I have a book in my car that talks about this, I'll have to go get it and look it up.
Originally Posted by Stephen Max
At low rpm this is true. At high rpm the the intake stroke and consequently the pulse width becomes so small that the injector switches from pulsing only during the intake stroke to pulsing even when the intake valve is closed, in order to get enough fuel to the cylinders.
There is a specific term for this, but I forget what it is. I think I have a book in my car that talks about this, I'll have to go get it and look it up.
There is a specific term for this, but I forget what it is. I think I have a book in my car that talks about this, I'll have to go get it and look it up.
Originally Posted by ejj
Interesting. No need to look it up on my behalf. That makes sense when I think about it.
Two variations of EFI systems are available: sequential and nonsequential. Sequential, which is the most common, pulses an injector in the same order as the firing order of the engine and in some cases according to the specific postion of the intake valve. In so doing, sequential pulses each injector every other revolution; that is, once per engine cycle. Nonsequential usually pulses all the injectors at the same time and on every revolution. Sequential EFI therefore usually has a pulse duration twice as long as nonsequential, but nonsequential pulses twice per engine cycle, thereby closely approximating delivery of sequential EFI. A clever variation on sequential injection is the ability to adjust exactly when the pulse occurs relatvie to the opening of the intake valve.
One might think pulsing the injector relative to the intake valve opening would be advantageous, but at higher rpm, the injector is open much longer than the valve. In fact, the injector can be open as much as 90% of the engine cycle time. Since the intake valve is open only about 40% of the cycle time, it is easy to see that sequencing the injector relative to the intake valve loses significance rapidly as the engine gains rpm. Therefore, sequential injection becomes a low-speed economy and emissions device, with no relationship to maximum power. Virtually all sequential injection systems stop sequencing at around 3000 rpm and revert to one pulse per revolution, the same as nonsequential. The distinction between the two types can therefore be ignored in calculating additional fuel flow as long as pulse duration is checked above approximately 4000 rpm. Then it is accurate to analyze available pulse increase based on one pulse per revolution.
It's interesting to note that the Maxima engine has a power dip then a surge in the 3000-4000 rpm range. That must be the injectors changing from sequential to nonsequential pulsing.
Originally Posted by Stephen Max
Too late, here is an excerpt from Supercharged! Design, Testing and Installation of Supercharger Systems, by Corky Bell:
Two variations of EFI systems are available: sequential and nonsequential. Sequential, which is the most common, pulses an injector in the same order as the firing order of the engine and in some cases according to the specific postion of the intake valve. In so doing, sequential pulses each injector every other revolution; that is, once per engine cycle. Nonsequential usually pulses all the injectors at the same time and on every revolution. Sequential EFI therefore usually has a pulse duration twice as long as nonsequential, but nonsequential pulses twice per engine cycle, thereby closely approximating delivery of sequential EFI. A clever variation on sequential injection is the ability to adjust exactly when the pulse occurs relatvie to the opening of the intake valve.
One might think pulsing the injector relative to the intake valve opening would be advantageous, but at higher rpm, the injector is open much longer than the valve. In fact, the injector can be open as much as 90% of the engine cycle time. Since the intake valve is open only about 40% of the cycle time, it is easy to see that sequencing the injector relative to the intake valve loses significance rapidly as the engine gains rpm. Therefore, sequential injection becomes a low-speed economy and emissions device, with no relationship to maximum power. Virtually all sequential injection systems stop sequencing at around 3000 rpm and revert to one pulse per revolution, the same as nonsequential. The distinction between the two types can therefore be ignored in calculating additional fuel flow as long as pulse duration is checked above approximately 4000 rpm. Then it is accurate to analyze available pulse increase based on one pulse per revolution.
It's interesting to note that the Maxima engine has a power dip then a surge in the 3000-4000 rpm range. That must be the injectors changing from sequential to nonsequential pulsing.
Two variations of EFI systems are available: sequential and nonsequential. Sequential, which is the most common, pulses an injector in the same order as the firing order of the engine and in some cases according to the specific postion of the intake valve. In so doing, sequential pulses each injector every other revolution; that is, once per engine cycle. Nonsequential usually pulses all the injectors at the same time and on every revolution. Sequential EFI therefore usually has a pulse duration twice as long as nonsequential, but nonsequential pulses twice per engine cycle, thereby closely approximating delivery of sequential EFI. A clever variation on sequential injection is the ability to adjust exactly when the pulse occurs relatvie to the opening of the intake valve.
One might think pulsing the injector relative to the intake valve opening would be advantageous, but at higher rpm, the injector is open much longer than the valve. In fact, the injector can be open as much as 90% of the engine cycle time. Since the intake valve is open only about 40% of the cycle time, it is easy to see that sequencing the injector relative to the intake valve loses significance rapidly as the engine gains rpm. Therefore, sequential injection becomes a low-speed economy and emissions device, with no relationship to maximum power. Virtually all sequential injection systems stop sequencing at around 3000 rpm and revert to one pulse per revolution, the same as nonsequential. The distinction between the two types can therefore be ignored in calculating additional fuel flow as long as pulse duration is checked above approximately 4000 rpm. Then it is accurate to analyze available pulse increase based on one pulse per revolution.
It's interesting to note that the Maxima engine has a power dip then a surge in the 3000-4000 rpm range. That must be the injectors changing from sequential to nonsequential pulsing.
Wonder if there's a dip (or bump) in most guys AFR at that same range. I've never paid that much attention. Time to hunt through the dyno forum!
Originally Posted by Stephen Max
Too late, here is an excerpt from Supercharged! Design, Testing and Installation of Supercharger Systems, by Corky Bell:
Two variations of EFI systems are available: sequential and nonsequential. Sequential, which is the most common, pulses an injector in the same order as the firing order of the engine and in some cases according to the specific postion of the intake valve. In so doing, sequential pulses each injector every other revolution; that is, once per engine cycle. Nonsequential usually pulses all the injectors at the same time and on every revolution. Sequential EFI therefore usually has a pulse duration twice as long as nonsequential, but nonsequential pulses twice per engine cycle, thereby closely approximating delivery of sequential EFI. A clever variation on sequential injection is the ability to adjust exactly when the pulse occurs relatvie to the opening of the intake valve.
One might think pulsing the injector relative to the intake valve opening would be advantageous, but at higher rpm, the injector is open much longer than the valve. In fact, the injector can be open as much as 90% of the engine cycle time. Since the intake valve is open only about 40% of the cycle time, it is easy to see that sequencing the injector relative to the intake valve loses significance rapidly as the engine gains rpm. Therefore, sequential injection becomes a low-speed economy and emissions device, with no relationship to maximum power. Virtually all sequential injection systems stop sequencing at around 3000 rpm and revert to one pulse per revolution, the same as nonsequential. The distinction between the two types can therefore be ignored in calculating additional fuel flow as long as pulse duration is checked above approximately 4000 rpm. Then it is accurate to analyze available pulse increase based on one pulse per revolution.
It's interesting to note that the Maxima engine has a power dip then a surge in the 3000-4000 rpm range. That must be the injectors changing from sequential to nonsequential pulsing.
Two variations of EFI systems are available: sequential and nonsequential. Sequential, which is the most common, pulses an injector in the same order as the firing order of the engine and in some cases according to the specific postion of the intake valve. In so doing, sequential pulses each injector every other revolution; that is, once per engine cycle. Nonsequential usually pulses all the injectors at the same time and on every revolution. Sequential EFI therefore usually has a pulse duration twice as long as nonsequential, but nonsequential pulses twice per engine cycle, thereby closely approximating delivery of sequential EFI. A clever variation on sequential injection is the ability to adjust exactly when the pulse occurs relatvie to the opening of the intake valve.
One might think pulsing the injector relative to the intake valve opening would be advantageous, but at higher rpm, the injector is open much longer than the valve. In fact, the injector can be open as much as 90% of the engine cycle time. Since the intake valve is open only about 40% of the cycle time, it is easy to see that sequencing the injector relative to the intake valve loses significance rapidly as the engine gains rpm. Therefore, sequential injection becomes a low-speed economy and emissions device, with no relationship to maximum power. Virtually all sequential injection systems stop sequencing at around 3000 rpm and revert to one pulse per revolution, the same as nonsequential. The distinction between the two types can therefore be ignored in calculating additional fuel flow as long as pulse duration is checked above approximately 4000 rpm. Then it is accurate to analyze available pulse increase based on one pulse per revolution.
It's interesting to note that the Maxima engine has a power dip then a surge in the 3000-4000 rpm range. That must be the injectors changing from sequential to nonsequential pulsing.
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sorry for bringing up this old thread:
I have a few question about the isntall:
so the box just have two wires according to the manufacturer. one is power and it can be tapped to the ignition. And where is the fuel injector singal wire? does anyone have a graph or picture? I assume it is one of the wire on ECU.
I have a few question about the isntall:
so the box just have two wires according to the manufacturer. one is power and it can be tapped to the ignition. And where is the fuel injector singal wire? does anyone have a graph or picture? I assume it is one of the wire on ECU.
Originally Posted by [maxi-overdose]
sorry for bringing up this old thread:
I have a few question about the isntall:
so the box just have two wires according to the manufacturer. one is power and it can be tapped to the ignition. And where is the fuel injector singal wire? does anyone have a graph or picture? I assume it is one of the wire on ECU.
I have a few question about the isntall:
so the box just have two wires according to the manufacturer. one is power and it can be tapped to the ignition. And where is the fuel injector singal wire? does anyone have a graph or picture? I assume it is one of the wire on ECU.
ECU pins:
According to my FSM:
Injector No. 1: 101 R/B
Injector No. 5: 102 L/W
Injector No. 2: 103 R/W
Injector No. 6: 104 PU/R
Injector No. 3: 105 R/Y
Injector No. 4: 107 R/L
Each injector bank is controlled separately, so if you're only going to only buy one, I'd monitor the bank closest to the firewall, ie 1, 3, or 5. Doesn't matter which injector you tap, since they're all controlled the same.
According to my FSM:
Injector No. 1: 101 R/B
Injector No. 5: 102 L/W
Injector No. 2: 103 R/W
Injector No. 6: 104 PU/R
Injector No. 3: 105 R/Y
Injector No. 4: 107 R/L
Each injector bank is controlled separately, so if you're only going to only buy one, I'd monitor the bank closest to the firewall, ie 1, 3, or 5. Doesn't matter which injector you tap, since they're all controlled the same.
Originally Posted by [maxi-overdose]
sorry for bringing up this old thread:
I have a few question about the isntall:
so the box just have two wires according to the manufacturer. one is power and it can be tapped to the ignition. And where is the fuel injector singal wire? does anyone have a graph or picture? I assume it is one of the wire on ECU.
I have a few question about the isntall:
so the box just have two wires according to the manufacturer. one is power and it can be tapped to the ignition. And where is the fuel injector singal wire? does anyone have a graph or picture? I assume it is one of the wire on ECU.
Originally Posted by [maxi-overdose]
thx Stephen and Alex for the tips and wiring instruction 
so Stephen, why did you choose to monitor injector #6? or just any injectors will be ok.
so Stephen, why did you choose to monitor injector #6? or just any injectors will be ok.
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