Author Topic: Odd stalling issue  (Read 5093 times)

Offline dnb

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Odd stalling issue
« on: August 19, 2015, 01:32:00 am »
I drove my TVR out of the garage for the first time in over a year (work gets in the way somewhat) and thought I better put some miles on the engine I built for it at the end of last year.  It can and does idle when cold, however nearly every time after driving it, I stop at the garage ready to open the door, and the car stalls.  I have plotted a chart to show the moment of one of the stalls.  (Sorry, no datalog of it at the moment due to finger trouble) 

I have to confess I am a little stumped by this particular issue, so any help is appreciated.  I have checked (several times) everything I can think of and the problem still happens.  I have been running 1.2.30 firmware with dual widebands for a while now and most of the time the car behaves very well.   I have the VEMS configured to control a fully sequential v8 (36-1 crank sensor and single tooth cam sensor), so use all 8 injection and ignition channels, the IAC stepper driver and most of the low power outputs to run the engine and ancillaries, and most of the available sensor inputs including 2 widebands and EGTs and a fuel temperature sensor, so it's a non-trivial configuration, but one I believe should work well.



The RPM drops like a stone, but neither the spark timing increase or IAC ramping up stop the stall happening.  They don't actually appear to have any effect at all on the RPM change.  The injector pulsewidth is not zero, so I assume the engine is getting fuel, and there is certainly air getting in to the cylinders because I used the throttle stop to open the throttles slightly to test this and it made no difference.  The only thing I haven't tried yet is totally disabling the idle control, but this seems like admitting defeat...

The whole thing seems like something has decided that the engine should not be running, so turns it off like a switch.  So what vital fact might I be missing here?  No doubt I have missed something obvious...

Offline gunni

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Re: Odd stalling issue
« Reply #1 on: August 20, 2015, 11:33:15 am »
Link to your map?

I think its worth doing a vemslog of this happening,that will help everybody give some support.

Offline fphil

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Re: Odd stalling issue
« Reply #2 on: August 20, 2015, 08:47:52 pm »
Nice instability, a feedback control running out of its domain can causes this. Are you cutting the ego corrections under 800rpm per ex.? On my car I had to increase the fuel @ about 0.7 bar 800 rpm as a barrier because the integral term of idle regulation does not catch up fast enough (I had to use small P)

Offline dnb

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Re: Odd stalling issue
« Reply #3 on: August 21, 2015, 12:32:40 am »
I thought EGO switched off at 950 RPM (big cam, so needed a bit more tolerance - this used to work reasonably well on the old engine) but I see from the config that it has got set to 700 and I can't remember when and why I did that - it could be just enough to cause a problem. 

Anyway, it's something simple (like I thought there would be) to fix next time I get out to the car.  I will not accidentally delete the log this time...