Connecting oscilloscope to car ignitions

[RKovach]

I have read that you can use a lab scope to check the secondary firing
patterns by connecting an inductive lead to the coil wire on #2 channel, and
connecting another lead to the #1 spark plug wire on #1 channel, and use it
to trigger the signal. This will show all the plugs, in the firing order, in
1 trace.
Can this somehow be used on a distributorless ignition system that does not
use 1 coil for all the plugs? Is it possible to use 5 pickups, for a 6 cyl.
engine, all wired together, and connect this to the #2 channel and connect
the #1 as above to get the same results?

 

[Bob Grimm]

Can this somehow be used on a distributorless ignition system that does not
use 1 coil for all the plugs? Is it possible to use 5 pickups, for a 6 cyl.
engine, all wired together, and connect this to the #2 channel and connect
the #1 as above to get the same results?

I assume you are referring to DIS (Direct Ignition) as oposed to COP
(Coil-on-plug) (another form of DIS) Ignition.

Unfortunately no you cannot just hook up 6 (for a six cyl) inductors
and view a readable pattern. Most DIS ignition systems fire the
coils in pairs with the secondary voltage travelling thru the current
cylinder to be fired and "returning" thru it's companion cylinders
plug/wire and back to the coil completing the circuit.

Unless it is an Automotive Scope that can be configured to handle/
filter that reverse polarity waste-spark you will not get an accurate
display of the firing lines.

This is also why a conventional rpm inductive pickup reads 2x
the acutal rpm when clipped to a DIS wire, since it reads that extra
waste-spark firing (during the cylinders exhaust stroke).

-BG

 

[Indian Summer]

I'm trying the same thing. My problem how do we capture infrequent events if
we're using normal scopes. If you succeed, please let me know. How does a
capacitive pickup work or an inductive lead? Anyone know?

Here take a look: This is a capacitive pickup which connects around the
insulation of an ignition circuit component such as a plug wire for scopes.

Secondary Ignition Pickup http://tinyurl.com/xoox

Indi