My no.4 cylinder injector channel blew up and ground'ed zero when i rev the engine until it bounces of the rev limiter hard (8500rpm for honda s2000 engine). So, I swap to another spare injector channel and replaced all the injectors, it works nicely for a few week until i rev it past the rev limiter and no.4 cylinder inject channel blew up again.
Is there any solution to this? other than changing the way I drive. ;D I use it for drifting, so I will need to keep on the limiter to stay on the power.
I'll ask the developers... Its strange that it's number 4 all the time - two FETs have died with the same injector.
It might be a co-incidence that it was the same injector - or it might be the injector causing it.
Just a thought, I'll ask some of the other people.
This sounds similar to a fault I had a couple of years ago.
The quick answer is that when the first FET died it caused damage to the FET driver IC, and from then on, any FET on that channel would be likely to die.
The easiest solution was to replace the injector FETs with IGBTs. This has worked well.
Again...
Some time ago I put some other MOSFETs for INJ outputs. Ratings seemed same as original ones. But I fried one after other when paired injectors on V8 was used.
Then I found in driver datasheet: drivers IC has not enough balancing capacitance (two 0.22uF capacitors for four driver ICs IIRC). And it could lead to overvoltage spikes to FET gates. Now I use additional 10uF ceramic capacitor for drivers 12V supply trace.
In problematic cases (e. g. may be short circuit somewhere/sometime) smartFETs are fine.
VNP5N07 for example.
Gints
While this is all well and good - its the fact that this installation has been run on the limiter for two years.
change fet to irf640n
Thanks for input guys.
Quote from: [email protected] on July 03, 2010, 06:12:15 PM
I'll ask the developers... Its strange that it's number 4 all the time - two FETs have died with the same injector.
It is the number 4, but not with the same injector because I have swap the injectors around for fault finding. My guess is probably the driver which controlling the no.4 cylinder FET is frying it... but hey.. i have very limited knowledge in electronics world and VEMs.
I have checked the resistance on all the injectors, they are all good.
Quote from: [email protected]
While this is all well and good - its the fact that this installation has been run on the limiter for two years
I didn't have limiter on my 20v, hence I blew it up when i mis-shift in 3rd.... my fault... lol..
Out of IGBT, capacitor or irf640 solution, which one is the best and fixable solution? because i have a race coming up this weekend.
thanks in advance!
probably to change to IGBTs - I'm not sure if dnb is saying that the FET driver will need to be changed.
If so, we need to figure out which driver chip is causing the problem, and group the injectors to the other driver.
My plan is to run the 4th cylinder on another spare inj FET for this weekend and be gently with the limiter, then I will have more time to play with it after the race.
Is there any guidance in changing it to IGBTs? I don't mind trying different things as it is a very good learning opportunity, however I will need more guidance in doing so. 8)
Which FET channels have broken?
We may have to swap some of the other FET connections around.
IGBTs will be opening the case and replacing the power transistors, so some soldering will be required.
Rob,
INJFET Ch.8 and Ch.64 are broken, so I still have Ch.128 and Ch.32 available to use.
All P259 channel are broken and I disabled them by cutting one of the leg off the chip.
Ch.16 is driving the rev counter.
I can get my mate to do the delicate soldering, do you have more information on replacing which and what on the board?
He should be able to get on with this: http://www.vems.hu/files/genboardv3/v3.3/v33_sch.pdf
When the PCB is removed from the box it should be straight forward, just a case of following the FETs from the pins on the PCB
(http://www.vems.hu/files/Fero/wiring/002.jpg)
Ok, sounds straight forward to me.
3 questions:
1. Is it just the case of replacing all the FET to a IGBT on the board. Providing they are physically identical?
2. Where to get those IGBTs? or any spec would help.
3. Any alteration to the loom or software?
dont use igbt from vems shop on fet place, becouse fets are driven with 12-14V and maximum source-gate voltage for igbt is 10V.
Put irf640n and 1uF condensator and check flyback wire.
Quote from: [email protected] on July 05, 2010, 06:17:02 AM
probably to change to IGBTs - I'm not sure if dnb is saying that the FET driver will need to be changed.
If you go for IGBTs there is no need to change the drivers.
Quote from: MWfire on July 05, 2010, 03:28:33 PM
dont use igbt from vems shop on fet place, becouse fets are driven with 12-14V and maximum source-gate voltage for igbt is 10V.
I suppose it is about 10V continuous voltage. Seems gate is protected from overvoltage. Internal protection elements generates heat if input voltage is higher.
I suggest VNP5N07. It is protected from almost all kinds of troubles...
The webshop IGBTs are fine for this (I had some spare, so I used them and know that they work), but there are better things available if you are buying new items.
These are the VNP5N07 FETs that Gints suggested:
http://uk.farnell.com/stmicroelectronics/vnp5n07-e/mosfet-smart-switch-to-220/dp/9804501?Ntt=VNP5N07
At £1.72 each you may as well get 12 - 8 of them to replace your injecter FETs, and four to fill the empty spaces in the ignition side of the board - as your P259 blew up you might want the extra channels to drive Fans, Fuel pumps and what have you...
There are ten FETs on the board, make sure that your mate only replaces the Injector FETs, and not the ones that go to the 18pin plug, as one of them drives the wideband and thats best left alone:
http://www.vems.co.uk/VEMS/WideBandO2.html
For IGBTs or smartfets or IRF640 (except IRF640FP) insulator sheet is necessary between enclosure and metallic pad.
All three has same pin arrangement as original FETs.
Ok... I will order 12x VNP5N07 as suggested. Thanks.
Will these new FET affect my MAP much? As in different opening and closing injection characteristic.
I would not expect any speed difference to be enough to change the fuelling.
You might want to play safe and get some of these:
http://uk.farnell.com/laird-technologies/ther-t-small/thermaflex-tube-to-220/dp/547566
Ok. I have the chips and insulator with me now. I will bring it to the track, just in case.
Well that's some hardcore race spares you're taking there.
Just don't forget the soldering tools, I had to re-solder a fuse on a car in the pits at Donnington with some bashed and well used Soldering iron courtesy of Driftworks' toolbox.
hmm.. just got back from the race. The engine just die after the first lap of practice and can't get it restarted until i reload the same map saved from my laptop.
Then, i had good 5 lap of hardcore hard reving in the following practice session. The engine was nice and strong.
but the no.4 cylinder FET decide to give up during the warm up of the qualifying session. not a happy bunny.
will swap all the inj fet next week
Quote from: MWfire on July 05, 2010, 03:28:33 PM
dont use igbt from vems shop on fet place, becouse fets are driven with 12-14V and maximum source-gate voltage for igbt is 10V.
Put irf640n and 1uF condensator and check flyback wire.
I have ran all IGTBs on all injector channels for over a year without problem, infact it was the only way I could stop smoking the FETs. I was advised to do so by the developers, in my case.
Sprocket, it isn't the only way indeed. And not most correct way also because recommended gate voltage exceeded at each injector pulse.
Fair enough, maybe its a matter of time before they fail, but so far I have had more success with the IGTBs up to 8000rpm which was better than 1200rpm and 30 seconds :D I am also not suggesting that it is the only fix :)
On second look at the datasheet, it states gate voltage of 12v pulsed and 10v continuous.
Most probably it will never fail. Ignition IGBTs has internal protection for gates.
but driving resistor can fail at big duty cyles if you have strange alternator(more than 14.4V).
Can I have some advice on desoldering the FET off the board. Me and my mate are having trouble with it. Cheers
Is everyone else as concerned as I am about how "fragile" these ECU's are in general? INJ FETs, P259, Flyback, etc.
Why is there such controversy about such a simple hardware issue?
I have installed 10 other brands of ECU and have never had an injector driver failure.
I did a Vi-PEC V44 last month, (old style with saturated drivers) and during diagnosing an unrelated car issue - the car was driven for several hours inadvertently with 2 ohm injectors (big no-no), and since then has been running flawless with Bosch 5 ohn 1600cc injectors.
With the VEMS I have 50+ ECU's that have never had a problem, and 5-10 that have had problems that nobody can pinpoint. That is simply a completely unacceptale failure rate.
The P259 problems really irriate me, sure I've never lost one since blowing it up on my first ecu, you then get it clear in your mind not to do it again - trouble is for a DIY ecu that means you've got the potential for a 1:1 failure, the reason for the seperation of grounds is a good one, and you'll find that theres better analog accuracy because of it.
FETs and IGBTs I've never personally had a problem with, and really a fuse should blow before a component like that would - most people think that its easier to "risk it" without a fuse. Sure there are cases like Tom70's here which I've not come across before.
Flyback is not uncommon on OEM ecus and if you decided to re-wire an existing ECU install and leave the flyback disconnected, you'd find the drivers failing. The flyback can be internally routed to the main ECU power supply but there were concerns about injecting high flyback voltages in directly to the components inside the case.
But there is something that shows a lack of completeness with these systems which I think is more about the software usability, upgrade path and configuration which makes these systems a nightmare to support, which is fine once you have a fully tested configuration, but it can be painful getting there. I'm pretty sure that other manufacturers have these issues with configuration (some I know do), but they're able to do the development in-house and send out fully configured and tested units with all the config closed to the user.
I know of one perticular manufacturer that boasted about how robust their ECU is and how they have never had a failure. I then had a chance to work on one of their engines, another story in itself, and found no spark. With no interface device, yes, thats right, you needed to spend anther £110 on software and an interface device to connect a PC, additional to an already expensive £550, suposedly robust ECU, that requires a non statdard dedicated connector that you cannot buy seperately so have to buy the complete loom. Only to have both ignition drivers fail. This was one of the manufacturers engines and it was their instalation, so it shouldn't have failed, but it did.
Its a bit like my work. I work for a manufacturer, and see loads of faults and issues with our machines, and if I were to just take that into consideration, I would have to think that the gear we manufacture was shite, when infact, the problems we see is only a tiny percentage of the machines we have in the field that we never ever see because they run perfectly without a problem for years.
One other thing to consider is that OEM ECU failures are not uncommon, and why there are loads Network 500 agents around the UK at least. The actual number of failures to cars on the road is tiny, but thats because of the multi million pound research programs OEMs have.
Ibuilt my own ECU and that is most likely why I had so many problems I did. I smoked the P259 chip trying to resolve the FET blowing by seperating out the grounds. like rob says, you do it once, and you dont do it again.
It is something wrong with hardware. I am not specialist of electronics. But now I think purpose is spikes on FET gates. And main reason could be too less balancing capatitance on FET drivers chips. There are four. But just two 0.22uF capacitors are used. Datasheet suggest :
QuoteSuggested capacitors are
a low inductance 0.1 uF ceramic in parallel with a 4.7 uF
tantalum. Additional bypass capacitors may be required
depending upon Drive Output loading and circuit layout.
Proper printed circuit board layout is extremely
critical and cannot be over emphasized.
For fet drivers manufacturers accent layout and balancing importance because of some inductive phenomena in long gates traces.
Now i use additional 10uF ceramic from rescue kit on each my board.
Gates seems most unprotected part. Some developers suggestion was to change respective FET driver chip for fried FET and then if it does not helps -
capacitors. I still can not imagine how driver can be damaged! These small chips are almost capable to drive injectors directly! But capacitors simply can be too small (it has huge tolerances like -20/+80%).
Other point - our local production ECU do not use flyback circuits at all. Many FETs are capable to suppress flyback spikes internally. And this ecu has no problems with FETs - much smaller smd ones with similar characteristics as ours. Also this says to me that most probably something from gate side is blameable.
But it is just my non-pro opinion.
Gints
Quote from: lugnuts on July 11, 2010, 08:21:48 PM
Is everyone else as concerned as I am about how "fragile" these ECU's are in general? INJ FETs, P259, Flyback, etc.
Why is there such controversy about such a simple hardware issue?
I have installed 10 other brands of ECU and have never had an injector driver failure.
I did a Vi-PEC V44 last month, (old style with saturated drivers) and during diagnosing an unrelated car issue - the car was driven for several hours inadvertently with 2 ohm injectors (big no-no), and since then has been running flawless with Bosch 5 ohn 1600cc injectors.
With the VEMS I have 50+ ECU's that have never had a problem, and 5-10 that have had problems that nobody can pinpoint. That is simply a completely unacceptale failure rate.
i allways use irf640n, put connection inside ecu for analog and power ground. So far more than 30ecu sold without any problem.
In my case I always use fully assembled ecu, and before that I used full assembled boards.
I have zero interest in re-designing and or repairing ecu's.
I have 100% interest in selling products that just "work".
I have been doing the Grounds and Flyback exactly to the recommended methods.
Nobody, I mean nobody else out there, uses fuses for the individual injector and ignition outputs.
It is very annoying to have to join analolg and power grounds.
No other ecu I work with has had any problem with "dirty or noisy alanog signals"
I hear "bad injectors, bad grounds" as excuses/reasons for Injector FET damage.
I never had injector cause ecu damage with other ecu. And if someone were to disconnect the ground, the engine would not run, you re-connect the ground, no issues, the engine simply starts and runs.
P259 - I have seen people recommend to not even bother using it.
It is also bad that if someone has a problem with the P259 - it can cause the car to not run due to loss of trigger.
Not all ecu companies are perfect. Autronic decided to change the design of their main firmware chip socket, to a surface mount soldering instead of thruhole.
That, and there was a boundry layer insulation problem with the chip itself that drove us nuts.
But I can honestly say, in 11 years of doing this, that no other ecu I work with has had a problem with injector driver that caused fuel to be dumped into a running engine.
I fully agree with Gints. Hardware design issue.
I believe he was the one last year who commented that the Autronic SMC has many many capacitors inside for protection.
<<<i allways use irf640n, put connection inside ecu for analog and power ground. So far more than 30ecu sold without any problem.>>>
- Please clarify this statement. What is the irf640n protecting? And how exactly do you join analog and power grounds?
IRF640n has 200V breakdown voltage. They don't fail even disconected flyback. Once they were driving high z and low z(1.9ohm) injectors in parallel without resistors and without pwm without problem.
For gnd
http://img155.imageshack.us/i/groundn.jpg/
Yes, but originally used FETs has built in diode for avalanche suppression at 60V. IMHO it should easily handle flyback spike from high imendance injector.
200V robust ones with gate protection: http://www.rohm.com/products/databook/tr/pdf/rdn100n20.pdf
You dont need individual fuses for the injectors, but if the case with these blowing FETs is due to capacitance issues then theres not going to be any fuse that helps you.
Why are you sticking with VEMS though for nearly 60 installs?
imho gate-source voltage isn't problem. Problem is bad flyback in some instalation. But if you put 200V mosfet then you have space for error.
And 1-3.3uF plastic(MKP) condesator is good between flyback and gnd.
The only way we'd know is to scope Tom70's offending channel when its driven hard - and unfortunately no one has the time or resources to do this, so we'll have to keep guessing.
BTW - What's the problem with the FET soldering Tom70?
BTW Megasquirt use almost same design of FET circuits. Usually on one FET two or more injectors connected.
FET driver chip is balanced with two capacitors as datasheet suggest to do. I do not remember any problems with irfiz34 60V ones.
Again my example of another ECU of our local production - no any flyback clamping circuits except built in MOSFET itself. http://www.irf.ru/pdf/irf7380.pdf VEMS FETs seems to me have much stronger avalanche suppression capabilities:
http://www.fairchildsemi.com/ds/FQ/FQPF20N06L.pdf
Both points above leads me to think that voltage spikes on gate is the cause. Yes spikes could be flyback sourced. And capacitor in this circuit simply makes it less noisy for overall wiring. And less noise means less chance feed it back to gate. You think no?
It is obvious that there has been a problem but we have been unable to recreate it.
So far I have never seen a FET failure in any of my test cars with the old FETs.
I have seen a FET failure that could be traced to one SARD injector on a customer car, when the injector was moved to an other cylinder that FET driver would fail shortly. I ended up fitting ignition IGBT's in that ECU to be able to use that set of injectors.
A number of modifications has been done over the years to try to find the problem where one of the last included a pretty big capcitor in the flyback circuit. This seems to have solved the problem. Soon after we also started using a far more robust FET, it should handle any flyback issues better. So far I have not heard of any FET failures since the last changes and the spec has remained the same for some time now.
Over the years we have done quite a few repairs and we have never seen problems with lowZ injectors, only with highZ injectors. So if you have experienced problems with lowZ injectors it is very likely that it has just been a short in the harness.
Jörgen
Quote from: tom70 on July 11, 2010, 07:25:20 PM
Can I have some advice on desoldering the FET off the board. Me and my mate are having trouble with it. Cheers
Simply cut the legs from the FET near the capsule and then desolder the legs one by one, this is by far the safest way to remove them. The old FET's should be thrown away in any case.
Jörgen
Quote from: [email protected] on July 12, 2010, 04:03:33 PM
BTW - What's the problem with the FET soldering Tom70?
We couldn't remove the old solder after melting it, maybe we need a stronger "solder" sucker. Maybe cutting the leg off will make things easier as Jorgen suggested.
Quote from: tom70 on July 13, 2010, 09:55:21 AM
We couldn't remove the old solder after melting it, maybe we need a stronger "solder" sucker. Maybe cutting the leg off will make things easier as Jorgen suggested.
Yes it will do, the package will be acting as a heat sink and drawing away the heat from the soldering iron.
I prefer using solder braid to solder suckers. Solder suckers can drop little balls of solder onto the board leaving you with intermittent shorts
I'd cut the package off, then heat the solder up and pull the leg out with tweezers/small pliers. Often you will find it easier if you add some solder when heating the leg to remove a component.
Then use the solder braid to clean the hole out
http://195.159.109.134/vemsuk/forum/index.php/topic,1342.msg14124.html