Blow injector channel when bouncing off the rev limiter hard

[tom70]

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. I use it for drifting, so I will need to keep on the limiter to stay on the power.

[rob@vems.co.uk]

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.

[dnb]

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.

[GintsK]

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

[rob@vems.co.uk]

While this is all well and good - its the fact that this installation has been run on the limiter for two years.

[MWfire]

change fet to irf640n

[tom70]

Thanks for input guys.

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.

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! 

[rob@vems.co.uk]

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.

[tom70]

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.

[rob@vems.co.uk]

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.

[tom70]

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?

[rob@vems.co.uk]

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

[tom70]

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?

[MWfire]

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.

[dnb]

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.