Dwell while cranking

rs2000 · Post by **rs2000** » Mon Aug 07, 2006 12:23 am

I've got a VB921 to control spark. I've been playing with it on the bench using a 12V bulb to represent the coil (ie to load up the VB921).

If i set the cranking dwell below about 6 ms the light flashes strangly. It goes flash flash flash nothing nothing nothing.. like 3 pulses on 3 pulses off.

If i disconnect the globe it flashes once every pulse, as expected.

Increacing the dwell to 6 ms or above cures it. I can get the same behavior on 029Q2 and 029l.

Is this normal and if so what is causing it to happen? How should cranking dwell be set?

Thanks

andrew

MS1 V2.2 029l

Post by **jsmcortina** » Mon Aug 07, 2006 5:13 am

What other settings do you have? Wheel decoder or not? What rpm are you testing at?

James

rs2000 · Post by **rs2000** » Mon Aug 07, 2006 5:28 am

No wheel decoder, on the stim with MSnS mode selected, LED 17 as spark output. Testing at cranking rpm which is about 200-300. I tested at a number of revs around that area with the same results. It is only while cranking, which for me means both banks of injectors pulse at the same time (instead of altenating) It only happens with load on the VB921 (ie my bulb) and as soon as i'm out of cranking mode its fine again.

Its a V2.2 board so the VB921 is mounted on its own board connected to the right of R26 with a 330 ohm resistor.

I cant seem to datalog spark pulses, if its possible let me know how and i'll log it happening.

andrew

Post by **jsmcortina** » Mon Aug 07, 2006 6:09 am

Could you post your MSQ please

James

rs2000 · Post by **rs2000** » Mon Aug 07, 2006 6:32 am

ok. I included the ini file for megatune too. It is a variation of keithmac's idle code

I managed to demonstrate a similar thing on 029Q2 with the msq that comes on it, only changing the spark stuff