Blown Injector FETs

[Sprocket]

Hm. Why alternate banks from h[0] is 0 only. With such setting only simultaneous firing is possible.

In the pic bellow the left settings are from a known good working set up with same family injector, but larger cc, and the right is the settings I have.

 

[Sprockets]

If the settings on the right are yours, and left is a running setup, then the big differnece is the PWM setting.  Yours is at 1ms, and the running is at 25.5 (ie, disabled).....this would give the fet something to work hard over!!!

-Gavin

[rob@vems.co.uk]

If injpwm DC is 100% then there's no PWM occuring

[Sprockets]

Which really, when you think about it......makes sense lol!

Must rememeber to start thinking more :p

-Gavin

[GintsK]

Sorry about 0 only: I have too small screen and I was lazy slide right side of picture visible.
 

If injpwm DC is 100% then there's no PWM occuring

Are you 100% sure 
IMHO 25.5ms and 100% is safer. I will scope this on the bench, if find time.

Correct PWMing can be Ubatt dependent: More % at low voltage, less at high.

But anyway. First component failed must be TVS diode if PWMing is active.

Gints

[Sprocket]

Had a thought

Would an inadequate, rather than poor ground cause FET failure?

The reason I say this is the ground point I am now using, is not the same one as that I have used on the 1400 which was the factory ground. I did however check the reisitance of this ground point to the battery, and there was no resistance. But, im now thinking that even though the ground resistance is fine, when its loaded up with current, it becomes a problem. I say this, As I know that it is a riv nut that I fitted, and I used some wax oil on the mating faces when I crimped it in.

First thing I will do is relocate this ground

Could this be the answer?

Could this also be the answer to blowing fuses on the ignition coils with slightly higher dwell times, and why the stepper driver doesnt seam to work correctly

[GintsK]

I do some labor work regarding injector settings.
PWMing can't kill your FETs. It is voltage dependant. But PWM% can only rise from configurated, when voltage falls. When voltage rises PWM% stays as configurated. 100% in this case. 14V seems is breakpoint.

But surprise!!! injrampup_battfac 4080 did not disable correction. It is maximal possible correction in fact!!
works in very strange way. It describe some kind of coefficient for inj_eff_rampup time. No influence @7V
If inj_eff_rampup time is configurated as 1500, it adds 1000us @7V. But injrampup_battfac scale this value @13V by aprox. :
4080 - 0.78
2000 - 0.89
500 -   0.97
0    -   1.0

So if injrampup_battfac is 4080 and inj_eff_rampup time is configurated as 1500 we get 1000*0.78=780us adder to PW @13V.
Very confusing and user unfriendly! Why, why

Both other settings are more straightforward:
Inj_open_time @13.2V is simple adder at any voltage. 1:1. 500us=500us
Battfact is PW added @7V It scales down to 0us @13.2V.

Sorry about offtopic! Rob, can you move it to appropriate place?

Gints

[rob@vems.co.uk]

It sounds like I need to clean this up and add it to the UserGuide.

[Sprocket]

Its bolloxed

[Sprocket]

I have calmed down a bit now

I have just ordered, 13 new FETs, 10 for me, and 3 to replace the ones I borrowed from Bat. Also ordered two TCP259 chips, to replace the one that smoked today Nobady's fault but mine for that one

Anyway. I am pulling the loom out tomorrow, and re hashing it with as short wire runs as possible, the ground will get extra care, and Im installing the ECU under the bonnet where it will not get wet.

I doubt the length of the loom is the problem as considering the size of the engine bay, its pretty small

The saga continues

Edit, Im going to feed each injector seperately and fuse them, any idea on the size of fuse that would survive, 5 amp?

[gunni]

http://ourworld.compuserve.com/homepages/Bill_Bowden/ohmslaw.htm
Voltage (E) = Current (I) * Resistance (R)
Power (watts) = Current Squared (I^2) * Resistance (R)
Power = I*E = E^2 / R

So each fuse has to be 1amp.
12v / 16ohm injector = 0.75amp

The 12v to the injectors would be
0.75 * 4 = 3amp, I´d go for 5amp fuse

[Jorgen]

Hi Gavin.

I would be worried about two things when desoldering a FET, you will heat it up a lot when desoldering it. That in itself can damage the FET but you can also likely to damage it with ESD when you handle it. FET's are VERY sensitive to ESD. I would NEVER try to reuse a semiconductor.
 
When you have blown a FET, regardless of why, you should always replace the FET drivers. They are often damaged when a FET shorts out and even if they seem to work we often see the FET's fail repeatedly if the FET driver isn't replaced.

So if a FET blows, replace the FET, the FET driver AND the FET that use the same FET driver.

If it happens again you should definately replace the capacitors servicing the FET drivers.

Also get rid of the 1.5KE30CA bidirectional transient suppressor diode, I am fairly certain that they have caused problems now and then. Use the 1.5KE30A unidirectional TS diode.

It is also safe to use IGBT's instead of FET's but you need to use them on all injectors on the same engine as they behave slightly different. I have used IGBT's on one car that recived a set of broken SARD highZ injectors. After running for two years with different injector types the SARD injectors went in and one of the FET's started blowing. Nothing short of fitting IGBT's fixed it.

What kind of injectors do you use?

Note that a 10A fuse will not protect a 15A semiconductor from a low resistance short. Never use a bigger fuse then you need.

It's not related to the injectors, but for the ignition the biggest acceptable fuse is 7.5A, unless you really know what you are doing.

Check that the flyback wire is properly connected and that the ground wires are max 150-200mm long and that they are joined like this: http://www.vems.se/forum/viewtopic.php?f=2&t=460

Stacked ring shaped cable ends is NOT acceptable, the above connection is pretty much the only connection that works in the long run.

I hope that this will help you get the car running again.

Jörgen Karlsson
Gothenburg, Sweden.

[Sprocket]

Cool

a little more work

However, where do I get the FET driver chip from? They are not in the webshop?

I may well have some in the rescue kit from the first board but I hed nothing with the second board, not even the inductor

Also, which capacitors do you speak of, are they the ones between the driver chips?

Excellent help, keep up the good work

[Sprocket]

Hang on, the driver chips are in the PWM Kit, lol, confusing

[Sprocket]

Oh, and Sprockets, is Gavin, Sprocket is Colin

Very confusing , I thought some one had hacked my account at first