dead vnd5n07
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dead vnd5n07
Just a note to the group. I lost an omnifet last week. Driving along and then injector #2 was full on! This is on a board I built with 2 - 2 channel fet drivers and 4 omnifets. The other 3 omnifets worked just fine and continue to . There was no electrical issue that I am aware of (no shorts, I was not 'playing with anything nor have I touched it in months). These should be protected against the release spike when the injector closes. Dunno what happened, but it was a bit scary.
This is my first component failure on a MS device since my initial install when I shorted the injector driver (single) fet and filled the engine with gas. THis was figuring how to mate the V2.2 board with my Saab's wiring harness.
Keith
This is my first component failure on a MS device since my initial install when I shorted the injector driver (single) fet and filled the engine with gas. THis was figuring how to mate the V2.2 board with my Saab's wiring harness.
Keith
Re: dead vnd5n07
I've lost several VNDs on customers' cars as well. They usually go at high rpm/load, when the duty cycle is high.
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Re: dead vnd5n07
The VNDs have protection circuitry at all ends and should in theory be very hard to destroy, yet there are still multiple reports of them dying. (http://www.msextra.com/forums/viewtopic ... 31&t=43083)
Was there a bad batch of them, or does anyone have a theory about why they die?
Was there a bad batch of them, or does anyone have a theory about why they die?
Joachim
1974 Jensen-Healey
1990 VW Caravelle Syncro - running MS3+X
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Re: dead vnd5n07
I found mine when I probed the gate. The fet driver, IXDN404, was not able to drive the gate any more. My schematic has a pull down resistor on the gate and a resistor inline to the gate from the fet driver. When it failed, I was in 3rd gear going about 15 mph. I pressed on the accelerator and then it was running on 3 cylinders. So, the PW was low then went high when they failed. Mine failed and never came back. These are Bosch -431 HiZ injectors.
KeithG
KeithG
Re: dead vnd5n07
All my cases were high Z as well, but probably on the low side of high (11.5-12R).
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Re: dead vnd5n07
Are these the injector drivers on the MS3x?
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Re: dead vnd5n07
Yes they are.Ute_Man wrote:Are these the injector drivers on the MS3x?
There are behind the scene plans to get a greater understanding of this. No results as of yet.
James
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Re: dead vnd5n07
I just scoped mine to look at the active clamp (internal to the device) to have a look. It clamps right at 39 volts.
If the internal clamp failed, then the device could/would get killed by the fly-back pulse from the injector coil. A secondary clamp in addition would provide protection if the active clamp died. Mine isn't running on the car yet but I imagine that a stuck ON injector isn't a good thing.
How far can one go to protect against this?
I was considering designing a watchdog to monitor injector pulses assuming that the pulse width never hits 100% ON, this could easily be done.
Do other ECUs do anything to protect against a dead driver?
Attached is a pic of the working vnd5n07 if anyone is interested.
If the internal clamp failed, then the device could/would get killed by the fly-back pulse from the injector coil. A secondary clamp in addition would provide protection if the active clamp died. Mine isn't running on the car yet but I imagine that a stuck ON injector isn't a good thing.
How far can one go to protect against this?
I was considering designing a watchdog to monitor injector pulses assuming that the pulse width never hits 100% ON, this could easily be done.
Do other ECUs do anything to protect against a dead driver?
Attached is a pic of the working vnd5n07 if anyone is interested.
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Re: dead vnd5n07
You can put a diode on a relay to help clamp the flyback, could you do the same at the injectors? Might not be the desired long term solution, but seems like it'd get rid of that 39v spike. Think a 1n4001 would do the trick, or would it need to be stronger/faster than that?
Brian
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Re: dead vnd5n07
The VND5N07 was purposefully designed to allow the flyback voltage to reach 60V. The higher voltage allows the injectors to close more quickly than if they were clamped to 12V with a 1N400x.UnaClocker wrote:You can put a diode on a relay to help clamp the flyback, could you do the same at the injectors? Might not be the desired long term solution, but seems like it'd get rid of that 39v spike. Think a 1n4001 would do the trick, or would it need to be stronger/faster than that?
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Re: dead vnd5n07
Interesting. So if it didn't clamp them at all, they'd close even faster? Allow the voltage to go up to whatever it wants?
Brian
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Re: dead vnd5n07
That's true in theory, but there are practical limitations to consider: such as the Vds/Vce of the switching MOSFET/transistor.UnaClocker wrote:Interesting. So if it didn't clamp them at all, they'd close even faster? Allow the voltage to go up to whatever it wants?
Re: dead vnd5n07
Could injectors be driven with IGBT's? Those things seem a lot more robust than MOSFETs, they take some pretty wicked flyback from the coils from time to time. (Sorry if I'm going off on a tangent here, always trying to expand my knowledge)
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Re: dead vnd5n07
Many different devices are suitable for driving injectors. Structurally, IGBT's are similar to a MOSFET driving a bipolar transistor. That alone doesn't make them anymore robust than a MOSFET, though. The IGBT's you're thinking of probably have built-in circuitry to protect against high voltages. The VND5N07 also has built-in circuitry for the same purpose, yet sometimes they fail.Ute_Man wrote:Could injectors be driven with IGBT's? Those things seem a lot more robust than MOSFETs, they take some pretty wicked flyback from the coils from time to time. (Sorry if I'm going off on a tangent here, always trying to expand my knowledge)
No one is sure that the flyback is what's damaging these VND5N07's anyway.
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Re: dead vnd5n07
Has anyone looked at it with a high resolution scope (like an Agilent 3000 or 7000)? There could be a short spike there that goes above 60V and over time wears out the protection circuit (or the FET itself). A slow sampling scope would miss the spike for sure. A transient protection diode may be faster than the internal circuit?EFIDART512 wrote:I just scoped mine to look at the active clamp (internal to the device) to have a look. It clamps right at 39 volts.
If the internal clamp failed, then the device could/would get killed by the fly-back pulse from the injector coil. A secondary clamp in addition would provide protection if the active clamp died. Mine isn't running on the car yet but I imagine that a stuck ON injector isn't a good thing.
[snip]
Attached is a pic of the working vnd5n07 if anyone is interested.
Joachim
1974 Jensen-Healey
1990 VW Caravelle Syncro - running MS3+X
2014 Ford Fiesta EcoBoost
1974 Jensen-Healey
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2014 Ford Fiesta EcoBoost
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Re: dead vnd5n07
Launching a theory here: Although the VND is internally ESD protected there are limits to how much they can take. Is there some common point in time and/or space all the failed components share? Could they have been mishandled somewhere before installation?SymTech Laboratories wrote:No one is sure that the flyback is what's damaging these VND5N07's anyway.
Joachim
1974 Jensen-Healey
1990 VW Caravelle Syncro - running MS3+X
2014 Ford Fiesta EcoBoost
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Re: dead vnd5n07
That's certainly a possibility, but we've seen failed VND5N07's on more than just the MS3X. As far as we know, they were all driving high impedance fuel injectors when they failed.subwoofer wrote:Launching a theory here: Although the VND is internally ESD protected there are limits to how much they can take. Is there some common point in time and/or space all the failed components share? Could they have been mishandled somewhere before installation?
Re: dead vnd5n07
I've also seen several failed VNDs on the sequential injection module offered by DIYAutoTune.com for the DIYPNP.
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Re: dead vnd5n07
Can you measure the gate to source resistance of the dead device?Keithg wrote:I found mine when I probed the gate. The fet driver, IXDN404, was not able to drive the gate any more. My schematic has a pull down resistor on the gate and a resistor inline to the gate from the fet driver. When it failed, I was in 3rd gear going about 15 mph. I pressed on the accelerator and then it was running on 3 cylinders. So, the PW was low then went high when they failed. Mine failed and never came back. These are Bosch -431 HiZ injectors.
KeithG
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Re: dead vnd5n07
We have a dead VND5N07 here, and the gate-to-source resistance is ~49k ohms, just like the working ones; so the status feedback circuit isn't enabled if that's what you're asking. It's interesting to note that the MOSFET's body diode seems to shorted: the Rd-to-s and Rs-to-d are both in the 200k ohm range. Perhaps there's a negative voltage at the drain causing the diode to conduct (e.g. flyback recovery overshoot).Peter Florance wrote:Can you measure the gate to source resistance of the dead device?