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heff0018 wrote:I understand why you would cut three slots in the harmonic balancer e.g 120 degrees for a 6 cylinder firing 3 times per crank rotation but with the crank trigger wheel with only one big slot how does the ignition/ECU where to fire? I assume the big slot is signifying TDC?

I'm confused. If your intention is to convert to crank trigger via Delco DIS then you need 7 slots, not 3, and you'd need to do one or the other, either cut 7 slots into your harmonic balancer or attach the 36:1 crank trigger wheel after removing all but 7 teeth.

Have you read this? viewtopic.php?f=15&t=128&hilit=dis

Don't worry so am I.

I am not at this stage converting to DIS. Thanks for that link I did start looking through it last night but didn't finish it. I quickly looked through it again and now I think I understand that VL400's DIS module recognises the big gap signifies TDC and it counts the gaps from there on. So this is different to how I would be using the crank trigger at this stage?? Maybe the 36 tooth wheel is not the right one. Should I have a solid wheel with 3 slots or slot the balancer as done by others. Cheers

so if your goal is to retain the dizzy, but move the trigger from the dizzy to the crank, so you can avoid the erratic timing that is a result of all the slop in timing chain and dizzy gears?
if so, then I guess there are normally 2 ways... if using a reluctor, and camira module, you could just take a 36 tooth wheel and knock all but 3 teeth, each tooth would pass the sensor at 10 deg timing, then feed the sensor to camira module and then put the single coil outlet into the dizzy still... that would give you more accurate rpm readings AND more stable timign than you would have feeding the module with a dizzy trigger.

for a 6 cylinder you need 3 slots in the dizzy or chopper wheel as the crank rotates 2 revolutions for one revolution of the dizzy..... so each slot gets read twice.

with VL400's ignition module and a 36-1 chopper wheel it uses the missing slot to know where TDC is, but then it just fires in wasted spark, so cyl 1 & 6 fire together, first revolution cyl 1 fires on the compression stroke, and 6 is on the exhaust stroke, then second revolution 6 is on the compression stroke and 1 on the exhaust .... the only way to get each cylinder to fire individually is with a cam sensor as well which tells the module when its back to the start of the firing order.

all the 3 slots in the balancer does (or a 3 slot chopper wheel) is allows you to use a CAS for firing the coil as apposed to the dizzy pickup, and really this only means probably less chance of getting a dodgy signal at higher revs from the play between crank/cam/dizzy gears...

in all honesty, if your not planning to use 6 coils or something like that, then there is really no reason to do any of this, just lock the dizzy, add camira ignition module to it and go on your way.

Jayme wrote:so if your goal is to retain the dizzy, but move the trigger from the dizzy to the crank, so you can avoid the erratic timing that is a result of all the slop in timing chain and dizzy gears?
if so, then I guess there are normally 2 ways... if using a reluctor, and camira module, you could just take a 36 tooth wheel and knock all but 3 teeth, each tooth would pass the sensor at 10 deg timing, then feed the sensor to camira module and then put the single coil outlet into the dizzy still... that would give you more accurate rpm readings AND more stable timign than you would have feeding the module with a dizzy trigger.

Yes that is correct at this stage and thanks that clears up a lot of my queries.

Holden202T wrote:for a 6 cylinder you need 3 slots in the dizzy or chopper wheel as the crank rotates 2 revolutions for one revolution of the dizzy..... so each slot gets read twice.

with VL400's ignition module and a 36-1 chopper wheel it uses the missing slot to know where TDC is, but then it just fires in wasted spark, so cyl 1 & 6 fire together, first revolution cyl 1 fires on the compression stroke, and 6 is on the exhaust stroke, then second revolution 6 is on the compression stroke and 1 on the exhaust .... the only way to get each cylinder to fire individually is with a cam sensor as well which tells the module when its back to the start of the firing order.

all the 3 slots in the balancer does (or a 3 slot chopper wheel) is allows you to use a CAS for firing the coil as apposed to the dizzy pickup, and really this only means probably less chance of getting a dodgy signal at higher revs from the play between crank/cam/dizzy gears...in all honesty, if your not planning to use 6 coils or something like that, then there is really no reason to do any of this, just lock the dizzy, add camira ignition module to it and go on your way.

Thanks, that covers the rest of my queries and will wait until I go for the 6 coils. Lots of other things to work on yet but a good learning process all the same. I have brand new timing gear installed and it has a cam button to stop cam walk + not high revving so all good for now.
Cheers

have a look at page 5 in this thread, theres some screen shots of data logs showing the difference in the trace for rpm.