Hey man
Thanks for your input before. I have tried everything I can imagine to get this to work and it just won't.

Heres a brief rundown

The car runs perfectly with the bosch external modules. Using pullup resistors and Spark output normal.

I have 2 VB921s in the prototype area with 1/4 of a Pentium1 headsink bolted to the back of each. They aren't getting too hot.

If I wire them like suggested in the extra page, they work and fire, but I'm guessing I have a horrible amount of noise being introduced into my VR Sensor Wires. (I use missing tooth)

If I have it all setup but just leave the coils disconnected I get normal rpm cranking around 200.

If I plug the coils in I get rpm blips to 700000rpm and its all over the place when cranking and running.

Internally I run 2 10A rated wires directly from the VB921 leg to the DB37 Pin (29 and 31 I'm using but it doesn't matter I don't think)

I also run an internal 10A wire ground strap from both VB921s to Pin1 on the DB37, which then runs off to the chassis ground

Basically, when megatune displays RPMs it is just reading off the CAS wire? Its definetly interferance causing the RPMs to go mad?

What steps can I take to get rid of all the interference?

 

the best way to reduce noise with vb921's is to mount them outside the MS case on a separate board somewhere, and ground them separately as well...

Also, try reducing the dwell, as if the dwell is too high, they'll go into current-limit mode, which is known to cause all kinds of nasty noise. If you're running COP coils with the vb921's they need very little dwell, like 1-1.5ms or so.

Ken

 

Problem wasn't dwell, I also removed the ground for the VB921s and made a wire direct to the ground I've been using successfully for everything else.

Still bad!

 

Is it possible for a faulty VB921 to do this?

 

I just tested the two individual VB921 circuits by driving the same coil with each by changing the coil plugs over.

I had an old lead and a BR8ET sparkplug sitting on the bonnet hinge.

With one circuit I get smooth cranking rpm in megatune ~160rpm,

with the other I can a rather eratic 200-320rpm display, so I just changed the VB921 that corresponds to that circuit with one of my ones destined for the trailing ignition. Hopefully the problem was just a esd (static) damaged VB921!

 

Same symptom is still there, and I verified the coil yesterday, so I'm sure its not the coil either.

 

Well I have reverted to using my big ugly hideously wired Bosch Ignition Modules again, if someone can shed some light on getting these VB921s working I will be very happy!

 

I'm going to try mounting the VBs external to my case today/tomorrow. Wonder if this will fix the problem. I will probably just use FC coilpacks if I need to mount the VB921s external to get them to work properly tho!

and it turns out the coil driver that wasn't causing any noise wasn't even firing the Coil, so thats why that one seemed to not be causing any problems