Mechanical/vacuum advance with ms firing coil

rs2000 · Post by **rs2000** » Tue Jun 20, 2006 9:46 pm

As the topic says i'm about to have another crack at spark control. I haven't had much luck in the past, and have had it stop working on me.

What i want to do intially is hook up a VB921 and the easy VR circuit i'm building and let ms fire the coil. I'd prefer not to lock down the dizzy right away, as if anything goes wrong when i'm out driving i want to be able to chuck the old ignition module back in to drive home. That way i can have the circuit and setup fully tested before commiting fully to the setup.

What i was thinking of doing was setting the ms trigger angle to 10* BTDC, and then setting the whole spark map to 10* so it fires the second it sees a trigger. Then the mechanical and vacuum advance will change the actual advance. Will this work or will it confuse ms?

thanks
andrew

ms V2.2, extra 029-l

Post by **jsmcortina** » Wed Jun 21, 2006 5:13 am

You aren't achieving anything by doing that. Plus, trying to fire at the same advance as the trigger is not necessarily reliable on the MS1/Extra code.

If you could arrange a crank trigger for the Megasquirt then you could leave the dizzy in place with no issues.

James

rs2000 · Post by **rs2000** » Wed Jun 21, 2006 9:37 am

yeah i know i'm not achieving anything by doing it, except that i can let ms control the coil for a few hundred kms without having to worry about how i'll get the car home if it stops working, since i'd still have everything original i could just swap the wires back and drive it as it is now. Basically it was an idea for proving my coil firing (VB921) and Easy VR circuit.

As i said in the first post the eventual goal is to wire up the mechanical advance and let ms control the advance. But seeing as firing at the trigger isn't reliable i might have to just go for it and cross my fingers!

thanks

andrew

Post by **jsmcortina** » Wed Jun 21, 2006 10:38 am

Like I said, can you add a crank trigger? On a 4 cyl this could be as simple as two longer bolts on the crank pulley or flywheel.

If you did that then you could very simply switch between MS spark control and distributor spark control. Plus it will give you more accurate timing.

James

milosch01 · Post by **milosch01** » Wed Jun 21, 2006 4:01 pm

There must be a way to lock down the distributor in a way which can be undone quickly. Perhaps tie-wraps would last long enough for you to test your MS ;) Otherwise, some small bolts tapped in might work to hold the weights in place.

rs2000 · Post by **rs2000** » Wed Jun 21, 2006 6:10 pm

Locking the dizzy requires taking the dizzy out and disassembling it from the bottom in order to get to the weights.. I can't really see how to do a more temporay solution without cutting/modifying it. James i was hoping to just use the distributor as the trigger to avoid having to install a crank angle sensor.

I think i'll just install it and hope it doesn't stop working. I suppose if it does i can always swap the circuit and just drive it home with locked timing.

andrew

milosch01 · Post by **milosch01** » Wed Jun 21, 2006 6:53 pm

Ah, ok. I was able to get to mine from the top. I think you will be happier in the long run with a trigger wheel, too. But definitely go this route first, because, in my experience, it's good to see the progression and try out all options. You will get to know your engine a lot better in the process.

rs2000 · Post by **rs2000** » Wed Jun 21, 2006 7:44 pm

Yeah thats what i though.. eventually i would like to try wasted spark with a 36-1 trigger wheel and 2 VB921's, but i thought i'd try a simpler method first to get some experience..

andrew