Diodes and Fuel Injectors
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Joined: Jun 2016
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From: Central Cal.
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Joined: Dec 2004
Posts: 2,178
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From: Florida
ive never heard of people adding them but ive heard of them being utilized inside ECUs for this purpose. Someone mentioned that the new haltech has some updated circuitry compared to their prior elite ecus on some of the outputs that close things quicker with a diode.
i dont think its a big problem these days though, i had 1000ccs on my 2l evo that idled fine, and my 5.3 has a relatively small cam and does fine with 1500s.
i dont think its a big problem these days though, i had 1000ccs on my 2l evo that idled fine, and my 5.3 has a relatively small cam and does fine with 1500s.
They're typically used with inductors in parallel but reverse to provide a current path when the EM field breaks down and the polarity across the inductor flips. Never seen a reason for doing it on an injector though. Maybe a coil lol.
TECH Enthusiast
Joined: Aug 2021
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Back ElectroMagnetic Forces ALL MOTORS that operate by using the flow of electrons, current flow, that causes a Magnetic Field.
This "field" can be around the wire, the coil around the Iron and has N/S polarity.
This Field when it is reduced, during Voltage being stopped, will cause current flow in the opposite direction,
when that voltage is high enough to DAMAGE the gate in the semiconductor causing a short.
Motors ARE ignition coils, fuel injectors, VVT actuators, NOS valves and other types of motors.
The "grounding" of the BEMF will also speed up the motors operation.
The use of a 1N5366 is one choice for an injector, MOST coil drivers, IGBTs, have "built in" diode protection.
This "field" can be around the wire, the coil around the Iron and has N/S polarity.
This Field when it is reduced, during Voltage being stopped, will cause current flow in the opposite direction,
when that voltage is high enough to DAMAGE the gate in the semiconductor causing a short.
Motors ARE ignition coils, fuel injectors, VVT actuators, NOS valves and other types of motors.
The "grounding" of the BEMF will also speed up the motors operation.
The use of a 1N5366 is one choice for an injector, MOST coil drivers, IGBTs, have "built in" diode protection.
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TECH Enthusiast
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Starter Shock, quite strong Yes, I have been shocked by the operation of a starter motor solenoid.
MANY here complain about engine bad running/missfire, etc.
The EMI of an ALT Diode, a blown shorted diode, will cause EMI.
The A/C clutch, the cooling fan motor(s), fuel pump, etc. can cause electrical noise.
The cure could be as simple as installing a MOV or a TVS.
Most modern cars have a CAN buss that does not like noise.
MANY here complain about engine bad running/missfire, etc.
The EMI of an ALT Diode, a blown shorted diode, will cause EMI.
The A/C clutch, the cooling fan motor(s), fuel pump, etc. can cause electrical noise.
The cure could be as simple as installing a MOV or a TVS.
Most modern cars have a CAN buss that does not like noise.
Yes, I have been shocked by the operation of a starter motor solenoid.
MANY here complain about engine bad running/missfire, etc.
The EMI of an ALT Diode, a blown shorted diode, will cause EMI.
The A/C clutch, the cooling fan motor(s), fuel pump, etc. can cause electrical noise.
The cure could be as simple as installing a MOV or a TVS.
Most modern cars have a CAN buss that does not like noise.
MANY here complain about engine bad running/missfire, etc.
The EMI of an ALT Diode, a blown shorted diode, will cause EMI.
The A/C clutch, the cooling fan motor(s), fuel pump, etc. can cause electrical noise.
The cure could be as simple as installing a MOV or a TVS.
Most modern cars have a CAN buss that does not like noise.
Thread Starter
TECH Fanatic
Joined: Nov 2014
Posts: 1,309
Likes: 660
Let's stay on topic. Let's keep it to Fuel Injectors.
So my buddy is having a hard time idling his 4 banger with 1500s. He's looking to get finer control of the injectors, with lower fuel delivery per pulse, at low pulse widths. He has heard that zener diodes can help him reduce the amount of fuel per pulse.
I don't think adding zener diodes to his existing setup will speed the closing of his injectors. My opinion is that the injector drive MOSFETS in his engine management, like most, have a built in diode to protect the mosfets and these diode slows down the closing of the injectors. Adding external diodes will only make it worse if the MOSFETS already have internal diodes. Any diodes shunting the voltage generated by the field in the injectors coil slows down that movement towards closing. But the diodes are necessary to protect the MOSFETS from high reverse voltages.
If you have a drive without internal protection diodes, then an external Zener that limits the reverse voltage to somewhere higher than 12 volts but low enough to protect the drive from high reverse voltage will probably speed the closing. But that would require a completely different drive method.
I also have an idea for another method to speed it up, but that requires an H bridge and is more complicated.
Lets keep the discussion to this topic.
So my buddy is having a hard time idling his 4 banger with 1500s. He's looking to get finer control of the injectors, with lower fuel delivery per pulse, at low pulse widths. He has heard that zener diodes can help him reduce the amount of fuel per pulse.
I don't think adding zener diodes to his existing setup will speed the closing of his injectors. My opinion is that the injector drive MOSFETS in his engine management, like most, have a built in diode to protect the mosfets and these diode slows down the closing of the injectors. Adding external diodes will only make it worse if the MOSFETS already have internal diodes. Any diodes shunting the voltage generated by the field in the injectors coil slows down that movement towards closing. But the diodes are necessary to protect the MOSFETS from high reverse voltages.
If you have a drive without internal protection diodes, then an external Zener that limits the reverse voltage to somewhere higher than 12 volts but low enough to protect the drive from high reverse voltage will probably speed the closing. But that would require a completely different drive method.
I also have an idea for another method to speed it up, but that requires an H bridge and is more complicated.
Lets keep the discussion to this topic.
Let's stay on topic. Let's keep it to Fuel Injectors.
So my buddy is having a hard time idling his 4 banger with 1500s. He's looking to get finer control of the injectors, with lower fuel delivery per pulse, at low pulse widths. He has heard that zener diodes can help him reduce the amount of fuel per pulse.
I don't think adding zener diodes to his existing setup will speed the closing of his injectors. My opinion is that the injector drive MOSFETS in his engine management, like most, have a built in diode to protect the mosfets and these diode slows down the closing of the injectors. Adding external diodes will only make it worse if the MOSFETS already have internal diodes. Any diodes shunting the voltage generated by the field in the injectors coil slows down that movement towards closing. But the diodes are necessary to protect the MOSFETS from high reverse voltages.
If you have a drive without internal protection diodes, then an external Zener that limits the reverse voltage to somewhere higher than 12 volts but low enough to protect the drive from high reverse voltage will probably speed the closing. But that would require a completely different drive method.
I also have an idea for another method to speed it up, but that requires an H bridge and is more complicated.
Lets keep the discussion to this topic.
So my buddy is having a hard time idling his 4 banger with 1500s. He's looking to get finer control of the injectors, with lower fuel delivery per pulse, at low pulse widths. He has heard that zener diodes can help him reduce the amount of fuel per pulse.
I don't think adding zener diodes to his existing setup will speed the closing of his injectors. My opinion is that the injector drive MOSFETS in his engine management, like most, have a built in diode to protect the mosfets and these diode slows down the closing of the injectors. Adding external diodes will only make it worse if the MOSFETS already have internal diodes. Any diodes shunting the voltage generated by the field in the injectors coil slows down that movement towards closing. But the diodes are necessary to protect the MOSFETS from high reverse voltages.
If you have a drive without internal protection diodes, then an external Zener that limits the reverse voltage to somewhere higher than 12 volts but low enough to protect the drive from high reverse voltage will probably speed the closing. But that would require a completely different drive method.
I also have an idea for another method to speed it up, but that requires an H bridge and is more complicated.
Lets keep the discussion to this topic.
Thread Starter
TECH Fanatic
Joined: Nov 2014
Posts: 1,309
Likes: 660
Draw a diagram of how you think it should be connected and I will test it. I have an injector calibration test set. Drivers I use are IRF540n.
Last edited by LSswap; Sep 14, 2021 at 12:54 PM.
I disagree. I believe that if the driver FET or Transistor has a protection diode, and they probably all do, then no improvement with flyback diode. The internal protection diode already acts as flyback diode. Any load on the reverse voltage from the coil slows down the movement of the aramature.
Draw a diagram of how you think it should be connected and I will test it. I have an injector calibration test set. Drivers I use are IRF540n.
Draw a diagram of how you think it should be connected and I will test it. I have an injector calibration test set. Drivers I use are IRF540n.
